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2821 lines
107 KiB
C++
2821 lines
107 KiB
C++
//===- SROA.cpp - Scalar Replacement Of Aggregates ------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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/// \file
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/// This transformation implements the well known scalar replacement of
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/// aggregates transformation. It tries to identify promotable elements of an
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/// aggregate alloca, and promote them to registers. It will also try to
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/// convert uses of an element (or set of elements) of an alloca into a vector
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/// or bitfield-style integer scalar if appropriate.
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///
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/// It works to do this with minimal slicing of the alloca so that regions
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/// which are merely transferred in and out of external memory remain unchanged
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/// and are not decomposed to scalar code.
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///
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/// Because this also performs alloca promotion, it can be thought of as also
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/// serving the purpose of SSA formation. The algorithm iterates on the
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/// function until all opportunities for promotion have been realized.
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///
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "sroa"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/DIBuilder.h"
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#include "llvm/DebugInfo.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/IRBuilder.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Module.h"
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#include "llvm/Operator.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/TinyPtrVector.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/Loads.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/GetElementPtrTypeIterator.h"
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#include "llvm/Support/InstVisitor.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/ValueHandle.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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using namespace llvm;
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STATISTIC(NumAllocasAnalyzed, "Number of allocas analyzed for replacement");
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STATISTIC(NumNewAllocas, "Number of new, smaller allocas introduced");
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STATISTIC(NumPromoted, "Number of allocas promoted to SSA values");
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STATISTIC(NumLoadsSpeculated, "Number of loads speculated to allow promotion");
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STATISTIC(NumDeleted, "Number of instructions deleted");
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STATISTIC(NumVectorized, "Number of vectorized aggregates");
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/// Hidden option to force the pass to not use DomTree and mem2reg, instead
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/// forming SSA values through the SSAUpdater infrastructure.
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static cl::opt<bool>
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ForceSSAUpdater("force-ssa-updater", cl::init(false), cl::Hidden);
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namespace {
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/// \brief Alloca partitioning representation.
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///
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/// This class represents a partitioning of an alloca into slices, and
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/// information about the nature of uses of each slice of the alloca. The goal
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/// is that this information is sufficient to decide if and how to split the
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/// alloca apart and replace slices with scalars. It is also intended that this
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/// structure can capture the relevant information needed both to decide about
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/// and to enact these transformations.
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class AllocaPartitioning {
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public:
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/// \brief A common base class for representing a half-open byte range.
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struct ByteRange {
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/// \brief The beginning offset of the range.
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uint64_t BeginOffset;
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/// \brief The ending offset, not included in the range.
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uint64_t EndOffset;
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ByteRange() : BeginOffset(), EndOffset() {}
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ByteRange(uint64_t BeginOffset, uint64_t EndOffset)
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: BeginOffset(BeginOffset), EndOffset(EndOffset) {}
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/// \brief Support for ordering ranges.
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///
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/// This provides an ordering over ranges such that start offsets are
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/// always increasing, and within equal start offsets, the end offsets are
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/// decreasing. Thus the spanning range comes first in a cluster with the
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/// same start position.
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bool operator<(const ByteRange &RHS) const {
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if (BeginOffset < RHS.BeginOffset) return true;
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if (BeginOffset > RHS.BeginOffset) return false;
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if (EndOffset > RHS.EndOffset) return true;
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return false;
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}
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/// \brief Support comparison with a single offset to allow binary searches.
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friend bool operator<(const ByteRange &LHS, uint64_t RHSOffset) {
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return LHS.BeginOffset < RHSOffset;
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}
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friend LLVM_ATTRIBUTE_UNUSED bool operator<(uint64_t LHSOffset,
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const ByteRange &RHS) {
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return LHSOffset < RHS.BeginOffset;
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}
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bool operator==(const ByteRange &RHS) const {
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return BeginOffset == RHS.BeginOffset && EndOffset == RHS.EndOffset;
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}
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bool operator!=(const ByteRange &RHS) const { return !operator==(RHS); }
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};
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/// \brief A partition of an alloca.
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///
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/// This structure represents a contiguous partition of the alloca. These are
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/// formed by examining the uses of the alloca. During formation, they may
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/// overlap but once an AllocaPartitioning is built, the Partitions within it
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/// are all disjoint.
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struct Partition : public ByteRange {
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/// \brief Whether this partition is splittable into smaller partitions.
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///
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/// We flag partitions as splittable when they are formed entirely due to
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/// accesses by trivially splittable operations such as memset and memcpy.
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///
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/// FIXME: At some point we should consider loads and stores of FCAs to be
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/// splittable and eagerly split them into scalar values.
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bool IsSplittable;
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Partition() : ByteRange(), IsSplittable() {}
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Partition(uint64_t BeginOffset, uint64_t EndOffset, bool IsSplittable)
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: ByteRange(BeginOffset, EndOffset), IsSplittable(IsSplittable) {}
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};
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/// \brief A particular use of a partition of the alloca.
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///
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/// This structure is used to associate uses of a partition with it. They
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/// mark the range of bytes which are referenced by a particular instruction,
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/// and includes a handle to the user itself and the pointer value in use.
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/// The bounds of these uses are determined by intersecting the bounds of the
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/// memory use itself with a particular partition. As a consequence there is
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/// intentionally overlap between various uses of the same partition.
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struct PartitionUse : public ByteRange {
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/// \brief The user of this range of the alloca.
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AssertingVH<Instruction> User;
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/// \brief The particular pointer value derived from this alloca in use.
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AssertingVH<Instruction> Ptr;
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PartitionUse() : ByteRange(), User(), Ptr() {}
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PartitionUse(uint64_t BeginOffset, uint64_t EndOffset,
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Instruction *User, Instruction *Ptr)
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: ByteRange(BeginOffset, EndOffset), User(User), Ptr(Ptr) {}
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};
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/// \brief Construct a partitioning of a particular alloca.
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///
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/// Construction does most of the work for partitioning the alloca. This
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/// performs the necessary walks of users and builds a partitioning from it.
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AllocaPartitioning(const TargetData &TD, AllocaInst &AI);
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/// \brief Test whether a pointer to the allocation escapes our analysis.
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///
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/// If this is true, the partitioning is never fully built and should be
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/// ignored.
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bool isEscaped() const { return PointerEscapingInstr; }
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/// \brief Support for iterating over the partitions.
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/// @{
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typedef SmallVectorImpl<Partition>::iterator iterator;
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iterator begin() { return Partitions.begin(); }
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iterator end() { return Partitions.end(); }
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typedef SmallVectorImpl<Partition>::const_iterator const_iterator;
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const_iterator begin() const { return Partitions.begin(); }
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const_iterator end() const { return Partitions.end(); }
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/// @}
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/// \brief Support for iterating over and manipulating a particular
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/// partition's uses.
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///
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/// The iteration support provided for uses is more limited, but also
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/// includes some manipulation routines to support rewriting the uses of
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/// partitions during SROA.
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/// @{
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typedef SmallVectorImpl<PartitionUse>::iterator use_iterator;
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use_iterator use_begin(unsigned Idx) { return Uses[Idx].begin(); }
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use_iterator use_begin(const_iterator I) { return Uses[I - begin()].begin(); }
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use_iterator use_end(unsigned Idx) { return Uses[Idx].end(); }
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use_iterator use_end(const_iterator I) { return Uses[I - begin()].end(); }
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void use_insert(unsigned Idx, use_iterator UI, const PartitionUse &U) {
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Uses[Idx].insert(UI, U);
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}
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void use_insert(const_iterator I, use_iterator UI, const PartitionUse &U) {
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Uses[I - begin()].insert(UI, U);
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}
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void use_erase(unsigned Idx, use_iterator UI) { Uses[Idx].erase(UI); }
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void use_erase(const_iterator I, use_iterator UI) {
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Uses[I - begin()].erase(UI);
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}
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typedef SmallVectorImpl<PartitionUse>::const_iterator const_use_iterator;
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const_use_iterator use_begin(unsigned Idx) const { return Uses[Idx].begin(); }
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const_use_iterator use_begin(const_iterator I) const {
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return Uses[I - begin()].begin();
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}
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const_use_iterator use_end(unsigned Idx) const { return Uses[Idx].end(); }
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const_use_iterator use_end(const_iterator I) const {
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return Uses[I - begin()].end();
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}
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/// @}
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/// \brief Allow iterating the dead users for this alloca.
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///
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/// These are instructions which will never actually use the alloca as they
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/// are outside the allocated range. They are safe to replace with undef and
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/// delete.
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/// @{
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typedef SmallVectorImpl<Instruction *>::const_iterator dead_user_iterator;
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dead_user_iterator dead_user_begin() const { return DeadUsers.begin(); }
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dead_user_iterator dead_user_end() const { return DeadUsers.end(); }
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/// @}
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/// \brief Allow iterating the dead expressions referring to this alloca.
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///
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/// These are operands which have cannot actually be used to refer to the
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/// alloca as they are outside its range and the user doesn't correct for
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/// that. These mostly consist of PHI node inputs and the like which we just
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/// need to replace with undef.
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/// @{
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typedef SmallVectorImpl<Use *>::const_iterator dead_op_iterator;
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dead_op_iterator dead_op_begin() const { return DeadOperands.begin(); }
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dead_op_iterator dead_op_end() const { return DeadOperands.end(); }
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/// @}
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/// \brief MemTransferInst auxiliary data.
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/// This struct provides some auxiliary data about memory transfer
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/// intrinsics such as memcpy and memmove. These intrinsics can use two
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/// different ranges within the same alloca, and provide other challenges to
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/// correctly represent. We stash extra data to help us untangle this
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/// after the partitioning is complete.
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struct MemTransferOffsets {
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uint64_t DestBegin, DestEnd;
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uint64_t SourceBegin, SourceEnd;
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bool IsSplittable;
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};
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MemTransferOffsets getMemTransferOffsets(MemTransferInst &II) const {
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return MemTransferInstData.lookup(&II);
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}
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/// \brief Map from a PHI or select operand back to a partition.
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///
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/// When manipulating PHI nodes or selects, they can use more than one
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/// partition of an alloca. We store a special mapping to allow finding the
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/// partition referenced by each of these operands, if any.
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iterator findPartitionForPHIOrSelectOperand(Instruction &I, Value *Op) {
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SmallDenseMap<std::pair<Instruction *, Value *>,
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std::pair<unsigned, unsigned> >::const_iterator MapIt
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= PHIOrSelectOpMap.find(std::make_pair(&I, Op));
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if (MapIt == PHIOrSelectOpMap.end())
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return end();
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return begin() + MapIt->second.first;
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}
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/// \brief Map from a PHI or select operand back to the specific use of
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/// a partition.
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///
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/// Similar to mapping these operands back to the partitions, this maps
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/// directly to the use structure of that partition.
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use_iterator findPartitionUseForPHIOrSelectOperand(Instruction &I,
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Value *Op) {
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SmallDenseMap<std::pair<Instruction *, Value *>,
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std::pair<unsigned, unsigned> >::const_iterator MapIt
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= PHIOrSelectOpMap.find(std::make_pair(&I, Op));
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assert(MapIt != PHIOrSelectOpMap.end());
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return Uses[MapIt->second.first].begin() + MapIt->second.second;
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}
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/// \brief Compute a common type among the uses of a particular partition.
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///
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/// This routines walks all of the uses of a particular partition and tries
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/// to find a common type between them. Untyped operations such as memset and
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/// memcpy are ignored.
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Type *getCommonType(iterator I) const;
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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void print(raw_ostream &OS, const_iterator I, StringRef Indent = " ") const;
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void printUsers(raw_ostream &OS, const_iterator I,
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StringRef Indent = " ") const;
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void print(raw_ostream &OS) const;
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void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump(const_iterator I) const;
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void LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED dump() const;
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#endif
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private:
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template <typename DerivedT, typename RetT = void> class BuilderBase;
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class PartitionBuilder;
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friend class AllocaPartitioning::PartitionBuilder;
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class UseBuilder;
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friend class AllocaPartitioning::UseBuilder;
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#ifndef NDEBUG
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/// \brief Handle to alloca instruction to simplify method interfaces.
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AllocaInst &AI;
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#endif
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/// \brief The instruction responsible for this alloca having no partitioning.
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///
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/// When an instruction (potentially) escapes the pointer to the alloca, we
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/// store a pointer to that here and abort trying to partition the alloca.
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/// This will be null if the alloca is partitioned successfully.
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Instruction *PointerEscapingInstr;
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/// \brief The partitions of the alloca.
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///
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/// We store a vector of the partitions over the alloca here. This vector is
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/// sorted by increasing begin offset, and then by decreasing end offset. See
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/// the Partition inner class for more details. Initially (during
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/// construction) there are overlaps, but we form a disjoint sequence of
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/// partitions while finishing construction and a fully constructed object is
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/// expected to always have this as a disjoint space.
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SmallVector<Partition, 8> Partitions;
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/// \brief The uses of the partitions.
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///
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/// This is essentially a mapping from each partition to a list of uses of
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/// that partition. The mapping is done with a Uses vector that has the exact
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/// same number of entries as the partition vector. Each entry is itself
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/// a vector of the uses.
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SmallVector<SmallVector<PartitionUse, 2>, 8> Uses;
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/// \brief Instructions which will become dead if we rewrite the alloca.
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///
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/// Note that these are not separated by partition. This is because we expect
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/// a partitioned alloca to be completely rewritten or not rewritten at all.
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/// If rewritten, all these instructions can simply be removed and replaced
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/// with undef as they come from outside of the allocated space.
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SmallVector<Instruction *, 8> DeadUsers;
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/// \brief Operands which will become dead if we rewrite the alloca.
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///
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/// These are operands that in their particular use can be replaced with
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/// undef when we rewrite the alloca. These show up in out-of-bounds inputs
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/// to PHI nodes and the like. They aren't entirely dead (there might be
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/// a GEP back into the bounds using it elsewhere) and nor is the PHI, but we
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/// want to swap this particular input for undef to simplify the use lists of
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/// the alloca.
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SmallVector<Use *, 8> DeadOperands;
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/// \brief The underlying storage for auxiliary memcpy and memset info.
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SmallDenseMap<MemTransferInst *, MemTransferOffsets, 4> MemTransferInstData;
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/// \brief A side datastructure used when building up the partitions and uses.
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///
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/// This mapping is only really used during the initial building of the
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/// partitioning so that we can retain information about PHI and select nodes
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/// processed.
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SmallDenseMap<Instruction *, std::pair<uint64_t, bool> > PHIOrSelectSizes;
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/// \brief Auxiliary information for particular PHI or select operands.
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SmallDenseMap<std::pair<Instruction *, Value *>,
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std::pair<unsigned, unsigned>, 4> PHIOrSelectOpMap;
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/// \brief A utility routine called from the constructor.
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///
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/// This does what it says on the tin. It is the key of the alloca partition
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/// splitting and merging. After it is called we have the desired disjoint
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/// collection of partitions.
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void splitAndMergePartitions();
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};
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}
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template <typename DerivedT, typename RetT>
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class AllocaPartitioning::BuilderBase
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: public InstVisitor<DerivedT, RetT> {
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public:
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BuilderBase(const TargetData &TD, AllocaInst &AI, AllocaPartitioning &P)
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: TD(TD),
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AllocSize(TD.getTypeAllocSize(AI.getAllocatedType())),
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P(P) {
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enqueueUsers(AI, 0);
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}
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protected:
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const TargetData &TD;
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const uint64_t AllocSize;
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AllocaPartitioning &P;
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struct OffsetUse {
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Use *U;
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uint64_t Offset;
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};
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SmallVector<OffsetUse, 8> Queue;
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// The active offset and use while visiting.
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Use *U;
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uint64_t Offset;
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void enqueueUsers(Instruction &I, uint64_t UserOffset) {
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SmallPtrSet<User *, 8> UserSet;
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for (Value::use_iterator UI = I.use_begin(), UE = I.use_end();
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UI != UE; ++UI) {
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if (!UserSet.insert(*UI))
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continue;
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OffsetUse OU = { &UI.getUse(), UserOffset };
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Queue.push_back(OU);
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}
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}
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bool computeConstantGEPOffset(GetElementPtrInst &GEPI, uint64_t &GEPOffset) {
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GEPOffset = Offset;
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for (gep_type_iterator GTI = gep_type_begin(GEPI), GTE = gep_type_end(GEPI);
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GTI != GTE; ++GTI) {
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ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
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if (!OpC)
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return false;
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if (OpC->isZero())
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continue;
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// Handle a struct index, which adds its field offset to the pointer.
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if (StructType *STy = dyn_cast<StructType>(*GTI)) {
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unsigned ElementIdx = OpC->getZExtValue();
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const StructLayout *SL = TD.getStructLayout(STy);
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GEPOffset += SL->getElementOffset(ElementIdx);
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continue;
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}
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GEPOffset
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+= OpC->getZExtValue() * TD.getTypeAllocSize(GTI.getIndexedType());
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}
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return true;
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}
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Value *foldSelectInst(SelectInst &SI) {
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// If the condition being selected on is a constant or the same value is
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// being selected between, fold the select. Yes this does (rarely) happen
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// early on.
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|
if (ConstantInt *CI = dyn_cast<ConstantInt>(SI.getCondition()))
|
|
return SI.getOperand(1+CI->isZero());
|
|
if (SI.getOperand(1) == SI.getOperand(2)) {
|
|
assert(*U == SI.getOperand(1));
|
|
return SI.getOperand(1);
|
|
}
|
|
return 0;
|
|
}
|
|
};
|
|
|
|
/// \brief Builder for the alloca partitioning.
|
|
///
|
|
/// This class builds an alloca partitioning by recursively visiting the uses
|
|
/// of an alloca and splitting the partitions for each load and store at each
|
|
/// offset.
|
|
class AllocaPartitioning::PartitionBuilder
|
|
: public BuilderBase<PartitionBuilder, bool> {
|
|
friend class InstVisitor<PartitionBuilder, bool>;
|
|
|
|
SmallDenseMap<Instruction *, unsigned> MemTransferPartitionMap;
|
|
|
|
public:
|
|
PartitionBuilder(const TargetData &TD, AllocaInst &AI, AllocaPartitioning &P)
|
|
: BuilderBase<PartitionBuilder, bool>(TD, AI, P) {}
|
|
|
|
/// \brief Run the builder over the allocation.
|
|
bool operator()() {
|
|
// Note that we have to re-evaluate size on each trip through the loop as
|
|
// the queue grows at the tail.
|
|
for (unsigned Idx = 0; Idx < Queue.size(); ++Idx) {
|
|
U = Queue[Idx].U;
|
|
Offset = Queue[Idx].Offset;
|
|
if (!visit(cast<Instruction>(U->getUser())))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
private:
|
|
bool markAsEscaping(Instruction &I) {
|
|
P.PointerEscapingInstr = &I;
|
|
return false;
|
|
}
|
|
|
|
void insertUse(Instruction &I, uint64_t Offset, uint64_t Size,
|
|
bool IsSplittable = false) {
|
|
uint64_t BeginOffset = Offset, EndOffset = Offset + Size;
|
|
|
|
// Completely skip uses which start outside of the allocation.
|
|
if (BeginOffset >= AllocSize) {
|
|
DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset
|
|
<< " which starts past the end of the " << AllocSize
|
|
<< " byte alloca:\n"
|
|
<< " alloca: " << P.AI << "\n"
|
|
<< " use: " << I << "\n");
|
|
return;
|
|
}
|
|
|
|
// Clamp the size to the allocation.
|
|
if (EndOffset > AllocSize) {
|
|
DEBUG(dbgs() << "WARNING: Clamping a " << Size << " byte use @" << Offset
|
|
<< " to remain within the " << AllocSize << " byte alloca:\n"
|
|
<< " alloca: " << P.AI << "\n"
|
|
<< " use: " << I << "\n");
|
|
EndOffset = AllocSize;
|
|
}
|
|
|
|
// See if we can just add a user onto the last slot currently occupied.
|
|
if (!P.Partitions.empty() &&
|
|
P.Partitions.back().BeginOffset == BeginOffset &&
|
|
P.Partitions.back().EndOffset == EndOffset) {
|
|
P.Partitions.back().IsSplittable &= IsSplittable;
|
|
return;
|
|
}
|
|
|
|
Partition New(BeginOffset, EndOffset, IsSplittable);
|
|
P.Partitions.push_back(New);
|
|
}
|
|
|
|
bool handleLoadOrStore(Type *Ty, Instruction &I, uint64_t Offset) {
|
|
uint64_t Size = TD.getTypeStoreSize(Ty);
|
|
|
|
// If this memory access can be shown to *statically* extend outside the
|
|
// bounds of of the allocation, it's behavior is undefined, so simply
|
|
// ignore it. Note that this is more strict than the generic clamping
|
|
// behavior of insertUse. We also try to handle cases which might run the
|
|
// risk of overflow.
|
|
// FIXME: We should instead consider the pointer to have escaped if this
|
|
// function is being instrumented for addressing bugs or race conditions.
|
|
if (Offset >= AllocSize || Size > AllocSize || Offset + Size > AllocSize) {
|
|
DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte "
|
|
<< (isa<LoadInst>(I) ? "load" : "store") << " @" << Offset
|
|
<< " which extends past the end of the " << AllocSize
|
|
<< " byte alloca:\n"
|
|
<< " alloca: " << P.AI << "\n"
|
|
<< " use: " << I << "\n");
|
|
return true;
|
|
}
|
|
|
|
insertUse(I, Offset, Size);
|
|
return true;
|
|
}
|
|
|
|
bool visitBitCastInst(BitCastInst &BC) {
|
|
enqueueUsers(BC, Offset);
|
|
return true;
|
|
}
|
|
|
|
bool visitGetElementPtrInst(GetElementPtrInst &GEPI) {
|
|
uint64_t GEPOffset;
|
|
if (!computeConstantGEPOffset(GEPI, GEPOffset))
|
|
return markAsEscaping(GEPI);
|
|
|
|
enqueueUsers(GEPI, GEPOffset);
|
|
return true;
|
|
}
|
|
|
|
bool visitLoadInst(LoadInst &LI) {
|
|
return handleLoadOrStore(LI.getType(), LI, Offset);
|
|
}
|
|
|
|
bool visitStoreInst(StoreInst &SI) {
|
|
if (SI.getOperand(0) == *U)
|
|
return markAsEscaping(SI);
|
|
|
|
return handleLoadOrStore(SI.getOperand(0)->getType(), SI, Offset);
|
|
}
|
|
|
|
|
|
bool visitMemSetInst(MemSetInst &II) {
|
|
assert(II.getRawDest() == *U && "Pointer use is not the destination?");
|
|
ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
|
|
uint64_t Size = Length ? Length->getZExtValue() : AllocSize - Offset;
|
|
insertUse(II, Offset, Size, Length);
|
|
return true;
|
|
}
|
|
|
|
bool visitMemTransferInst(MemTransferInst &II) {
|
|
ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
|
|
uint64_t Size = Length ? Length->getZExtValue() : AllocSize - Offset;
|
|
if (!Size)
|
|
// Zero-length mem transfer intrinsics can be ignored entirely.
|
|
return true;
|
|
|
|
MemTransferOffsets &Offsets = P.MemTransferInstData[&II];
|
|
|
|
// Only intrinsics with a constant length can be split.
|
|
Offsets.IsSplittable = Length;
|
|
|
|
if (*U != II.getRawDest()) {
|
|
assert(*U == II.getRawSource());
|
|
Offsets.SourceBegin = Offset;
|
|
Offsets.SourceEnd = Offset + Size;
|
|
} else {
|
|
Offsets.DestBegin = Offset;
|
|
Offsets.DestEnd = Offset + Size;
|
|
}
|
|
|
|
insertUse(II, Offset, Size, Offsets.IsSplittable);
|
|
unsigned NewIdx = P.Partitions.size() - 1;
|
|
|
|
SmallDenseMap<Instruction *, unsigned>::const_iterator PMI;
|
|
bool Inserted = false;
|
|
llvm::tie(PMI, Inserted)
|
|
= MemTransferPartitionMap.insert(std::make_pair(&II, NewIdx));
|
|
if (!Inserted && Offsets.IsSplittable) {
|
|
// We've found a memory transfer intrinsic which refers to the alloca as
|
|
// both a source and dest. We refuse to split these to simplify splitting
|
|
// logic. If possible, SROA will still split them into separate allocas
|
|
// and then re-analyze.
|
|
Offsets.IsSplittable = false;
|
|
P.Partitions[PMI->second].IsSplittable = false;
|
|
P.Partitions[NewIdx].IsSplittable = false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
// Disable SRoA for any intrinsics except for lifetime invariants.
|
|
// FIXME: What about debug instrinsics? This matches old behavior, but
|
|
// doesn't make sense.
|
|
bool visitIntrinsicInst(IntrinsicInst &II) {
|
|
if (II.getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II.getIntrinsicID() == Intrinsic::lifetime_end) {
|
|
ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
|
|
uint64_t Size = std::min(AllocSize - Offset, Length->getLimitedValue());
|
|
insertUse(II, Offset, Size, true);
|
|
return true;
|
|
}
|
|
|
|
return markAsEscaping(II);
|
|
}
|
|
|
|
Instruction *hasUnsafePHIOrSelectUse(Instruction *Root, uint64_t &Size) {
|
|
// We consider any PHI or select that results in a direct load or store of
|
|
// the same offset to be a viable use for partitioning purposes. These uses
|
|
// are considered unsplittable and the size is the maximum loaded or stored
|
|
// size.
|
|
SmallPtrSet<Instruction *, 4> Visited;
|
|
SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
|
|
Visited.insert(Root);
|
|
Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
|
|
do {
|
|
Instruction *I, *UsedI;
|
|
llvm::tie(UsedI, I) = Uses.pop_back_val();
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
|
|
Size = std::max(Size, TD.getTypeStoreSize(LI->getType()));
|
|
continue;
|
|
}
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
|
|
Value *Op = SI->getOperand(0);
|
|
if (Op == UsedI)
|
|
return SI;
|
|
Size = std::max(Size, TD.getTypeStoreSize(Op->getType()));
|
|
continue;
|
|
}
|
|
|
|
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
|
|
if (!GEP->hasAllZeroIndices())
|
|
return GEP;
|
|
} else if (!isa<BitCastInst>(I) && !isa<PHINode>(I) &&
|
|
!isa<SelectInst>(I)) {
|
|
return I;
|
|
}
|
|
|
|
for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
|
|
++UI)
|
|
if (Visited.insert(cast<Instruction>(*UI)))
|
|
Uses.push_back(std::make_pair(I, cast<Instruction>(*UI)));
|
|
} while (!Uses.empty());
|
|
|
|
return 0;
|
|
}
|
|
|
|
bool visitPHINode(PHINode &PN) {
|
|
// See if we already have computed info on this node.
|
|
std::pair<uint64_t, bool> &PHIInfo = P.PHIOrSelectSizes[&PN];
|
|
if (PHIInfo.first) {
|
|
PHIInfo.second = true;
|
|
insertUse(PN, Offset, PHIInfo.first);
|
|
return true;
|
|
}
|
|
|
|
// Check for an unsafe use of the PHI node.
|
|
if (Instruction *EscapingI = hasUnsafePHIOrSelectUse(&PN, PHIInfo.first))
|
|
return markAsEscaping(*EscapingI);
|
|
|
|
insertUse(PN, Offset, PHIInfo.first);
|
|
return true;
|
|
}
|
|
|
|
bool visitSelectInst(SelectInst &SI) {
|
|
if (Value *Result = foldSelectInst(SI)) {
|
|
if (Result == *U)
|
|
// If the result of the constant fold will be the pointer, recurse
|
|
// through the select as if we had RAUW'ed it.
|
|
enqueueUsers(SI, Offset);
|
|
|
|
return true;
|
|
}
|
|
|
|
// See if we already have computed info on this node.
|
|
std::pair<uint64_t, bool> &SelectInfo = P.PHIOrSelectSizes[&SI];
|
|
if (SelectInfo.first) {
|
|
SelectInfo.second = true;
|
|
insertUse(SI, Offset, SelectInfo.first);
|
|
return true;
|
|
}
|
|
|
|
// Check for an unsafe use of the PHI node.
|
|
if (Instruction *EscapingI = hasUnsafePHIOrSelectUse(&SI, SelectInfo.first))
|
|
return markAsEscaping(*EscapingI);
|
|
|
|
insertUse(SI, Offset, SelectInfo.first);
|
|
return true;
|
|
}
|
|
|
|
/// \brief Disable SROA entirely if there are unhandled users of the alloca.
|
|
bool visitInstruction(Instruction &I) { return markAsEscaping(I); }
|
|
};
|
|
|
|
|
|
/// \brief Use adder for the alloca partitioning.
|
|
///
|
|
/// This class adds the uses of an alloca to all of the partitions which they
|
|
/// use. For splittable partitions, this can end up doing essentially a linear
|
|
/// walk of the partitions, but the number of steps remains bounded by the
|
|
/// total result instruction size:
|
|
/// - The number of partitions is a result of the number unsplittable
|
|
/// instructions using the alloca.
|
|
/// - The number of users of each partition is at worst the total number of
|
|
/// splittable instructions using the alloca.
|
|
/// Thus we will produce N * M instructions in the end, where N are the number
|
|
/// of unsplittable uses and M are the number of splittable. This visitor does
|
|
/// the exact same number of updates to the partitioning.
|
|
///
|
|
/// In the more common case, this visitor will leverage the fact that the
|
|
/// partition space is pre-sorted, and do a logarithmic search for the
|
|
/// partition needed, making the total visit a classical ((N + M) * log(N))
|
|
/// complexity operation.
|
|
class AllocaPartitioning::UseBuilder : public BuilderBase<UseBuilder> {
|
|
friend class InstVisitor<UseBuilder>;
|
|
|
|
/// \brief Set to de-duplicate dead instructions found in the use walk.
|
|
SmallPtrSet<Instruction *, 4> VisitedDeadInsts;
|
|
|
|
public:
|
|
UseBuilder(const TargetData &TD, AllocaInst &AI, AllocaPartitioning &P)
|
|
: BuilderBase<UseBuilder>(TD, AI, P) {}
|
|
|
|
/// \brief Run the builder over the allocation.
|
|
void operator()() {
|
|
// Note that we have to re-evaluate size on each trip through the loop as
|
|
// the queue grows at the tail.
|
|
for (unsigned Idx = 0; Idx < Queue.size(); ++Idx) {
|
|
U = Queue[Idx].U;
|
|
Offset = Queue[Idx].Offset;
|
|
this->visit(cast<Instruction>(U->getUser()));
|
|
}
|
|
}
|
|
|
|
private:
|
|
void markAsDead(Instruction &I) {
|
|
if (VisitedDeadInsts.insert(&I))
|
|
P.DeadUsers.push_back(&I);
|
|
}
|
|
|
|
void insertUse(Instruction &User, uint64_t Offset, uint64_t Size) {
|
|
uint64_t BeginOffset = Offset, EndOffset = Offset + Size;
|
|
|
|
// If the use extends outside of the allocation, record it as a dead use
|
|
// for elimination later.
|
|
if (BeginOffset >= AllocSize || Size == 0)
|
|
return markAsDead(User);
|
|
|
|
// Bound the use by the size of the allocation.
|
|
if (EndOffset > AllocSize)
|
|
EndOffset = AllocSize;
|
|
|
|
// NB: This only works if we have zero overlapping partitions.
|
|
iterator B = std::lower_bound(P.begin(), P.end(), BeginOffset);
|
|
if (B != P.begin() && llvm::prior(B)->EndOffset > BeginOffset)
|
|
B = llvm::prior(B);
|
|
for (iterator I = B, E = P.end(); I != E && I->BeginOffset < EndOffset;
|
|
++I) {
|
|
PartitionUse NewUse(std::max(I->BeginOffset, BeginOffset),
|
|
std::min(I->EndOffset, EndOffset),
|
|
&User, cast<Instruction>(*U));
|
|
P.Uses[I - P.begin()].push_back(NewUse);
|
|
if (isa<PHINode>(U->getUser()) || isa<SelectInst>(U->getUser()))
|
|
P.PHIOrSelectOpMap[std::make_pair(&User, U->get())]
|
|
= std::make_pair(I - P.begin(), P.Uses[I - P.begin()].size() - 1);
|
|
}
|
|
}
|
|
|
|
void handleLoadOrStore(Type *Ty, Instruction &I, uint64_t Offset) {
|
|
uint64_t Size = TD.getTypeStoreSize(Ty);
|
|
|
|
// If this memory access can be shown to *statically* extend outside the
|
|
// bounds of of the allocation, it's behavior is undefined, so simply
|
|
// ignore it. Note that this is more strict than the generic clamping
|
|
// behavior of insertUse.
|
|
if (Offset >= AllocSize || Size > AllocSize || Offset + Size > AllocSize)
|
|
return markAsDead(I);
|
|
|
|
insertUse(I, Offset, Size);
|
|
}
|
|
|
|
void visitBitCastInst(BitCastInst &BC) {
|
|
if (BC.use_empty())
|
|
return markAsDead(BC);
|
|
|
|
enqueueUsers(BC, Offset);
|
|
}
|
|
|
|
void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
|
|
if (GEPI.use_empty())
|
|
return markAsDead(GEPI);
|
|
|
|
uint64_t GEPOffset;
|
|
if (!computeConstantGEPOffset(GEPI, GEPOffset))
|
|
llvm_unreachable("Unable to compute constant offset for use");
|
|
|
|
enqueueUsers(GEPI, GEPOffset);
|
|
}
|
|
|
|
void visitLoadInst(LoadInst &LI) {
|
|
handleLoadOrStore(LI.getType(), LI, Offset);
|
|
}
|
|
|
|
void visitStoreInst(StoreInst &SI) {
|
|
handleLoadOrStore(SI.getOperand(0)->getType(), SI, Offset);
|
|
}
|
|
|
|
void visitMemSetInst(MemSetInst &II) {
|
|
ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
|
|
uint64_t Size = Length ? Length->getZExtValue() : AllocSize - Offset;
|
|
insertUse(II, Offset, Size);
|
|
}
|
|
|
|
void visitMemTransferInst(MemTransferInst &II) {
|
|
ConstantInt *Length = dyn_cast<ConstantInt>(II.getLength());
|
|
uint64_t Size = Length ? Length->getZExtValue() : AllocSize - Offset;
|
|
insertUse(II, Offset, Size);
|
|
}
|
|
|
|
void visitIntrinsicInst(IntrinsicInst &II) {
|
|
assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II.getIntrinsicID() == Intrinsic::lifetime_end);
|
|
|
|
ConstantInt *Length = cast<ConstantInt>(II.getArgOperand(0));
|
|
insertUse(II, Offset,
|
|
std::min(AllocSize - Offset, Length->getLimitedValue()));
|
|
}
|
|
|
|
void insertPHIOrSelect(Instruction &User, uint64_t Offset) {
|
|
uint64_t Size = P.PHIOrSelectSizes.lookup(&User).first;
|
|
|
|
// For PHI and select operands outside the alloca, we can't nuke the entire
|
|
// phi or select -- the other side might still be relevant, so we special
|
|
// case them here and use a separate structure to track the operands
|
|
// themselves which should be replaced with undef.
|
|
if (Offset >= AllocSize) {
|
|
P.DeadOperands.push_back(U);
|
|
return;
|
|
}
|
|
|
|
insertUse(User, Offset, Size);
|
|
}
|
|
void visitPHINode(PHINode &PN) {
|
|
if (PN.use_empty())
|
|
return markAsDead(PN);
|
|
|
|
insertPHIOrSelect(PN, Offset);
|
|
}
|
|
void visitSelectInst(SelectInst &SI) {
|
|
if (SI.use_empty())
|
|
return markAsDead(SI);
|
|
|
|
if (Value *Result = foldSelectInst(SI)) {
|
|
if (Result == *U)
|
|
// If the result of the constant fold will be the pointer, recurse
|
|
// through the select as if we had RAUW'ed it.
|
|
enqueueUsers(SI, Offset);
|
|
|
|
return;
|
|
}
|
|
|
|
insertPHIOrSelect(SI, Offset);
|
|
}
|
|
|
|
/// \brief Unreachable, we've already visited the alloca once.
|
|
void visitInstruction(Instruction &I) {
|
|
llvm_unreachable("Unhandled instruction in use builder.");
|
|
}
|
|
};
|
|
|
|
void AllocaPartitioning::splitAndMergePartitions() {
|
|
size_t NumDeadPartitions = 0;
|
|
|
|
// Track the range of splittable partitions that we pass when accumulating
|
|
// overlapping unsplittable partitions.
|
|
uint64_t SplitEndOffset = 0ull;
|
|
|
|
Partition New(0ull, 0ull, false);
|
|
|
|
for (unsigned i = 0, j = i, e = Partitions.size(); i != e; i = j) {
|
|
++j;
|
|
|
|
if (!Partitions[i].IsSplittable || New.BeginOffset == New.EndOffset) {
|
|
assert(New.BeginOffset == New.EndOffset);
|
|
New = Partitions[i];
|
|
} else {
|
|
assert(New.IsSplittable);
|
|
New.EndOffset = std::max(New.EndOffset, Partitions[i].EndOffset);
|
|
}
|
|
assert(New.BeginOffset != New.EndOffset);
|
|
|
|
// Scan the overlapping partitions.
|
|
while (j != e && New.EndOffset > Partitions[j].BeginOffset) {
|
|
// If the new partition we are forming is splittable, stop at the first
|
|
// unsplittable partition.
|
|
if (New.IsSplittable && !Partitions[j].IsSplittable)
|
|
break;
|
|
|
|
// Grow the new partition to include any equally splittable range. 'j' is
|
|
// always equally splittable when New is splittable, but when New is not
|
|
// splittable, we may subsume some (or part of some) splitable partition
|
|
// without growing the new one.
|
|
if (New.IsSplittable == Partitions[j].IsSplittable) {
|
|
New.EndOffset = std::max(New.EndOffset, Partitions[j].EndOffset);
|
|
} else {
|
|
assert(!New.IsSplittable);
|
|
assert(Partitions[j].IsSplittable);
|
|
SplitEndOffset = std::max(SplitEndOffset, Partitions[j].EndOffset);
|
|
}
|
|
|
|
Partitions[j].BeginOffset = Partitions[j].EndOffset = UINT64_MAX;
|
|
++NumDeadPartitions;
|
|
++j;
|
|
}
|
|
|
|
// If the new partition is splittable, chop off the end as soon as the
|
|
// unsplittable subsequent partition starts and ensure we eventually cover
|
|
// the splittable area.
|
|
if (j != e && New.IsSplittable) {
|
|
SplitEndOffset = std::max(SplitEndOffset, New.EndOffset);
|
|
New.EndOffset = std::min(New.EndOffset, Partitions[j].BeginOffset);
|
|
}
|
|
|
|
// Add the new partition if it differs from the original one and is
|
|
// non-empty. We can end up with an empty partition here if it was
|
|
// splittable but there is an unsplittable one that starts at the same
|
|
// offset.
|
|
if (New != Partitions[i]) {
|
|
if (New.BeginOffset != New.EndOffset)
|
|
Partitions.push_back(New);
|
|
// Mark the old one for removal.
|
|
Partitions[i].BeginOffset = Partitions[i].EndOffset = UINT64_MAX;
|
|
++NumDeadPartitions;
|
|
}
|
|
|
|
New.BeginOffset = New.EndOffset;
|
|
if (!New.IsSplittable) {
|
|
New.EndOffset = std::max(New.EndOffset, SplitEndOffset);
|
|
if (j != e && !Partitions[j].IsSplittable)
|
|
New.EndOffset = std::min(New.EndOffset, Partitions[j].BeginOffset);
|
|
New.IsSplittable = true;
|
|
// If there is a trailing splittable partition which won't be fused into
|
|
// the next splittable partition go ahead and add it onto the partitions
|
|
// list.
|
|
if (New.BeginOffset < New.EndOffset &&
|
|
(j == e || !Partitions[j].IsSplittable ||
|
|
New.EndOffset < Partitions[j].BeginOffset)) {
|
|
Partitions.push_back(New);
|
|
New.BeginOffset = New.EndOffset = 0ull;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Re-sort the partitions now that they have been split and merged into
|
|
// disjoint set of partitions. Also remove any of the dead partitions we've
|
|
// replaced in the process.
|
|
std::sort(Partitions.begin(), Partitions.end());
|
|
if (NumDeadPartitions) {
|
|
assert(Partitions.back().BeginOffset == UINT64_MAX);
|
|
assert(Partitions.back().EndOffset == UINT64_MAX);
|
|
assert((ptrdiff_t)NumDeadPartitions ==
|
|
std::count(Partitions.begin(), Partitions.end(), Partitions.back()));
|
|
}
|
|
Partitions.erase(Partitions.end() - NumDeadPartitions, Partitions.end());
|
|
}
|
|
|
|
AllocaPartitioning::AllocaPartitioning(const TargetData &TD, AllocaInst &AI)
|
|
:
|
|
#ifndef NDEBUG
|
|
AI(AI),
|
|
#endif
|
|
PointerEscapingInstr(0) {
|
|
PartitionBuilder PB(TD, AI, *this);
|
|
if (!PB())
|
|
return;
|
|
|
|
if (Partitions.size() > 1) {
|
|
// Sort the uses. This arranges for the offsets to be in ascending order,
|
|
// and the sizes to be in descending order.
|
|
std::sort(Partitions.begin(), Partitions.end());
|
|
|
|
// Intersect splittability for all partitions with equal offsets and sizes.
|
|
// Then remove all but the first so that we have a sequence of non-equal but
|
|
// potentially overlapping partitions.
|
|
for (iterator I = Partitions.begin(), J = I, E = Partitions.end(); I != E;
|
|
I = J) {
|
|
++J;
|
|
while (J != E && *I == *J) {
|
|
I->IsSplittable &= J->IsSplittable;
|
|
++J;
|
|
}
|
|
}
|
|
Partitions.erase(std::unique(Partitions.begin(), Partitions.end()),
|
|
Partitions.end());
|
|
|
|
// Split splittable and merge unsplittable partitions into a disjoint set
|
|
// of partitions over the used space of the allocation.
|
|
splitAndMergePartitions();
|
|
}
|
|
|
|
// Now build up the user lists for each of these disjoint partitions by
|
|
// re-walking the recursive users of the alloca.
|
|
Uses.resize(Partitions.size());
|
|
UseBuilder UB(TD, AI, *this);
|
|
UB();
|
|
for (iterator I = Partitions.begin(), E = Partitions.end(); I != E; ++I)
|
|
std::stable_sort(use_begin(I), use_end(I));
|
|
}
|
|
|
|
Type *AllocaPartitioning::getCommonType(iterator I) const {
|
|
Type *Ty = 0;
|
|
for (const_use_iterator UI = use_begin(I), UE = use_end(I); UI != UE; ++UI) {
|
|
if (isa<MemIntrinsic>(*UI->User))
|
|
continue;
|
|
if (UI->BeginOffset != I->BeginOffset || UI->EndOffset != I->EndOffset)
|
|
break;
|
|
|
|
Type *UserTy = 0;
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(&*UI->User)) {
|
|
UserTy = LI->getType();
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(&*UI->User)) {
|
|
UserTy = SI->getValueOperand()->getType();
|
|
} else if (SelectInst *SI = dyn_cast<SelectInst>(&*UI->User)) {
|
|
if (PointerType *PtrTy = dyn_cast<PointerType>(SI->getType()))
|
|
UserTy = PtrTy->getElementType();
|
|
} else if (PHINode *PN = dyn_cast<PHINode>(&*UI->User)) {
|
|
if (PointerType *PtrTy = dyn_cast<PointerType>(PN->getType()))
|
|
UserTy = PtrTy->getElementType();
|
|
}
|
|
|
|
if (Ty && Ty != UserTy)
|
|
return 0;
|
|
|
|
Ty = UserTy;
|
|
}
|
|
return Ty;
|
|
}
|
|
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
|
|
void AllocaPartitioning::print(raw_ostream &OS, const_iterator I,
|
|
StringRef Indent) const {
|
|
OS << Indent << "partition #" << (I - begin())
|
|
<< " [" << I->BeginOffset << "," << I->EndOffset << ")"
|
|
<< (I->IsSplittable ? " (splittable)" : "")
|
|
<< (Uses[I - begin()].empty() ? " (zero uses)" : "")
|
|
<< "\n";
|
|
}
|
|
|
|
void AllocaPartitioning::printUsers(raw_ostream &OS, const_iterator I,
|
|
StringRef Indent) const {
|
|
for (const_use_iterator UI = use_begin(I), UE = use_end(I);
|
|
UI != UE; ++UI) {
|
|
OS << Indent << " [" << UI->BeginOffset << "," << UI->EndOffset << ") "
|
|
<< "used by: " << *UI->User << "\n";
|
|
if (MemTransferInst *II = dyn_cast<MemTransferInst>(&*UI->User)) {
|
|
const MemTransferOffsets &MTO = MemTransferInstData.lookup(II);
|
|
bool IsDest;
|
|
if (!MTO.IsSplittable)
|
|
IsDest = UI->BeginOffset == MTO.DestBegin;
|
|
else
|
|
IsDest = MTO.DestBegin != 0u;
|
|
OS << Indent << " (original " << (IsDest ? "dest" : "source") << ": "
|
|
<< "[" << (IsDest ? MTO.DestBegin : MTO.SourceBegin)
|
|
<< "," << (IsDest ? MTO.DestEnd : MTO.SourceEnd) << ")\n";
|
|
}
|
|
}
|
|
}
|
|
|
|
void AllocaPartitioning::print(raw_ostream &OS) const {
|
|
if (PointerEscapingInstr) {
|
|
OS << "No partitioning for alloca: " << AI << "\n"
|
|
<< " A pointer to this alloca escaped by:\n"
|
|
<< " " << *PointerEscapingInstr << "\n";
|
|
return;
|
|
}
|
|
|
|
OS << "Partitioning of alloca: " << AI << "\n";
|
|
unsigned Num = 0;
|
|
for (const_iterator I = begin(), E = end(); I != E; ++I, ++Num) {
|
|
print(OS, I);
|
|
printUsers(OS, I);
|
|
}
|
|
}
|
|
|
|
void AllocaPartitioning::dump(const_iterator I) const { print(dbgs(), I); }
|
|
void AllocaPartitioning::dump() const { print(dbgs()); }
|
|
|
|
#endif // !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
|
|
|
|
namespace {
|
|
/// \brief Implementation of LoadAndStorePromoter for promoting allocas.
|
|
///
|
|
/// This subclass of LoadAndStorePromoter adds overrides to handle promoting
|
|
/// the loads and stores of an alloca instruction, as well as updating its
|
|
/// debug information. This is used when a domtree is unavailable and thus
|
|
/// mem2reg in its full form can't be used to handle promotion of allocas to
|
|
/// scalar values.
|
|
class AllocaPromoter : public LoadAndStorePromoter {
|
|
AllocaInst &AI;
|
|
DIBuilder &DIB;
|
|
|
|
SmallVector<DbgDeclareInst *, 4> DDIs;
|
|
SmallVector<DbgValueInst *, 4> DVIs;
|
|
|
|
public:
|
|
AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
|
|
AllocaInst &AI, DIBuilder &DIB)
|
|
: LoadAndStorePromoter(Insts, S), AI(AI), DIB(DIB) {}
|
|
|
|
void run(const SmallVectorImpl<Instruction*> &Insts) {
|
|
// Remember which alloca we're promoting (for isInstInList).
|
|
if (MDNode *DebugNode = MDNode::getIfExists(AI.getContext(), &AI)) {
|
|
for (Value::use_iterator UI = DebugNode->use_begin(),
|
|
UE = DebugNode->use_end();
|
|
UI != UE; ++UI)
|
|
if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
|
|
DDIs.push_back(DDI);
|
|
else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(*UI))
|
|
DVIs.push_back(DVI);
|
|
}
|
|
|
|
LoadAndStorePromoter::run(Insts);
|
|
AI.eraseFromParent();
|
|
while (!DDIs.empty())
|
|
DDIs.pop_back_val()->eraseFromParent();
|
|
while (!DVIs.empty())
|
|
DVIs.pop_back_val()->eraseFromParent();
|
|
}
|
|
|
|
virtual bool isInstInList(Instruction *I,
|
|
const SmallVectorImpl<Instruction*> &Insts) const {
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I))
|
|
return LI->getOperand(0) == &AI;
|
|
return cast<StoreInst>(I)->getPointerOperand() == &AI;
|
|
}
|
|
|
|
virtual void updateDebugInfo(Instruction *Inst) const {
|
|
for (SmallVector<DbgDeclareInst *, 4>::const_iterator I = DDIs.begin(),
|
|
E = DDIs.end(); I != E; ++I) {
|
|
DbgDeclareInst *DDI = *I;
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
|
|
ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
|
|
else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
|
|
ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
|
|
}
|
|
for (SmallVector<DbgValueInst *, 4>::const_iterator I = DVIs.begin(),
|
|
E = DVIs.end(); I != E; ++I) {
|
|
DbgValueInst *DVI = *I;
|
|
Value *Arg = NULL;
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
// If an argument is zero extended then use argument directly. The ZExt
|
|
// may be zapped by an optimization pass in future.
|
|
if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
|
|
Arg = dyn_cast<Argument>(ZExt->getOperand(0));
|
|
if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
|
|
Arg = dyn_cast<Argument>(SExt->getOperand(0));
|
|
if (!Arg)
|
|
Arg = SI->getOperand(0);
|
|
} else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
|
|
Arg = LI->getOperand(0);
|
|
} else {
|
|
continue;
|
|
}
|
|
Instruction *DbgVal =
|
|
DIB.insertDbgValueIntrinsic(Arg, 0, DIVariable(DVI->getVariable()),
|
|
Inst);
|
|
DbgVal->setDebugLoc(DVI->getDebugLoc());
|
|
}
|
|
}
|
|
};
|
|
} // end anon namespace
|
|
|
|
|
|
namespace {
|
|
/// \brief An optimization pass providing Scalar Replacement of Aggregates.
|
|
///
|
|
/// This pass takes allocations which can be completely analyzed (that is, they
|
|
/// don't escape) and tries to turn them into scalar SSA values. There are
|
|
/// a few steps to this process.
|
|
///
|
|
/// 1) It takes allocations of aggregates and analyzes the ways in which they
|
|
/// are used to try to split them into smaller allocations, ideally of
|
|
/// a single scalar data type. It will split up memcpy and memset accesses
|
|
/// as necessary and try to isolate invidual scalar accesses.
|
|
/// 2) It will transform accesses into forms which are suitable for SSA value
|
|
/// promotion. This can be replacing a memset with a scalar store of an
|
|
/// integer value, or it can involve speculating operations on a PHI or
|
|
/// select to be a PHI or select of the results.
|
|
/// 3) Finally, this will try to detect a pattern of accesses which map cleanly
|
|
/// onto insert and extract operations on a vector value, and convert them to
|
|
/// this form. By doing so, it will enable promotion of vector aggregates to
|
|
/// SSA vector values.
|
|
class SROA : public FunctionPass {
|
|
const bool RequiresDomTree;
|
|
|
|
LLVMContext *C;
|
|
const TargetData *TD;
|
|
DominatorTree *DT;
|
|
|
|
/// \brief Worklist of alloca instructions to simplify.
|
|
///
|
|
/// Each alloca in the function is added to this. Each new alloca formed gets
|
|
/// added to it as well to recursively simplify unless that alloca can be
|
|
/// directly promoted. Finally, each time we rewrite a use of an alloca other
|
|
/// the one being actively rewritten, we add it back onto the list if not
|
|
/// already present to ensure it is re-visited.
|
|
SetVector<AllocaInst *, SmallVector<AllocaInst *, 16> > Worklist;
|
|
|
|
/// \brief A collection of instructions to delete.
|
|
/// We try to batch deletions to simplify code and make things a bit more
|
|
/// efficient.
|
|
SmallVector<Instruction *, 8> DeadInsts;
|
|
|
|
/// \brief A set to prevent repeatedly marking an instruction split into many
|
|
/// uses as dead. Only used to guard insertion into DeadInsts.
|
|
SmallPtrSet<Instruction *, 4> DeadSplitInsts;
|
|
|
|
/// \brief A collection of alloca instructions we can directly promote.
|
|
std::vector<AllocaInst *> PromotableAllocas;
|
|
|
|
public:
|
|
SROA(bool RequiresDomTree = true)
|
|
: FunctionPass(ID), RequiresDomTree(RequiresDomTree),
|
|
C(0), TD(0), DT(0) {
|
|
initializeSROAPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
bool runOnFunction(Function &F);
|
|
void getAnalysisUsage(AnalysisUsage &AU) const;
|
|
|
|
const char *getPassName() const { return "SROA"; }
|
|
static char ID;
|
|
|
|
private:
|
|
friend class AllocaPartitionRewriter;
|
|
friend class AllocaPartitionVectorRewriter;
|
|
|
|
bool rewriteAllocaPartition(AllocaInst &AI,
|
|
AllocaPartitioning &P,
|
|
AllocaPartitioning::iterator PI);
|
|
bool splitAlloca(AllocaInst &AI, AllocaPartitioning &P);
|
|
bool runOnAlloca(AllocaInst &AI);
|
|
void deleteDeadInstructions(SmallPtrSet<AllocaInst *, 4> &DeletedAllocas);
|
|
bool promoteAllocas(Function &F);
|
|
};
|
|
}
|
|
|
|
char SROA::ID = 0;
|
|
|
|
FunctionPass *llvm::createSROAPass(bool RequiresDomTree) {
|
|
return new SROA(RequiresDomTree);
|
|
}
|
|
|
|
INITIALIZE_PASS_BEGIN(SROA, "sroa", "Scalar Replacement Of Aggregates",
|
|
false, false)
|
|
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
|
|
INITIALIZE_PASS_END(SROA, "sroa", "Scalar Replacement Of Aggregates",
|
|
false, false)
|
|
|
|
/// \brief Accumulate the constant offsets in a GEP into a single APInt offset.
|
|
///
|
|
/// If the provided GEP is all-constant, the total byte offset formed by the
|
|
/// GEP is computed and Offset is set to it. If the GEP has any non-constant
|
|
/// operands, the function returns false and the value of Offset is unmodified.
|
|
static bool accumulateGEPOffsets(const TargetData &TD, GEPOperator &GEP,
|
|
APInt &Offset) {
|
|
APInt GEPOffset(Offset.getBitWidth(), 0);
|
|
for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
|
|
GTI != GTE; ++GTI) {
|
|
ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
|
|
if (!OpC)
|
|
return false;
|
|
if (OpC->isZero()) continue;
|
|
|
|
// Handle a struct index, which adds its field offset to the pointer.
|
|
if (StructType *STy = dyn_cast<StructType>(*GTI)) {
|
|
unsigned ElementIdx = OpC->getZExtValue();
|
|
const StructLayout *SL = TD.getStructLayout(STy);
|
|
GEPOffset += APInt(Offset.getBitWidth(),
|
|
SL->getElementOffset(ElementIdx));
|
|
continue;
|
|
}
|
|
|
|
APInt TypeSize(Offset.getBitWidth(),
|
|
TD.getTypeAllocSize(GTI.getIndexedType()));
|
|
if (VectorType *VTy = dyn_cast<VectorType>(*GTI)) {
|
|
assert((VTy->getScalarSizeInBits() % 8) == 0 &&
|
|
"vector element size is not a multiple of 8, cannot GEP over it");
|
|
TypeSize = VTy->getScalarSizeInBits() / 8;
|
|
}
|
|
|
|
GEPOffset += OpC->getValue().sextOrTrunc(Offset.getBitWidth()) * TypeSize;
|
|
}
|
|
Offset = GEPOffset;
|
|
return true;
|
|
}
|
|
|
|
/// \brief Build a GEP out of a base pointer and indices.
|
|
///
|
|
/// This will return the BasePtr if that is valid, or build a new GEP
|
|
/// instruction using the IRBuilder if GEP-ing is needed.
|
|
static Value *buildGEP(IRBuilder<> &IRB, Value *BasePtr,
|
|
SmallVectorImpl<Value *> &Indices,
|
|
const Twine &Prefix) {
|
|
if (Indices.empty())
|
|
return BasePtr;
|
|
|
|
// A single zero index is a no-op, so check for this and avoid building a GEP
|
|
// in that case.
|
|
if (Indices.size() == 1 && cast<ConstantInt>(Indices.back())->isZero())
|
|
return BasePtr;
|
|
|
|
return IRB.CreateInBoundsGEP(BasePtr, Indices, Prefix + ".idx");
|
|
}
|
|
|
|
/// \brief Get a natural GEP off of the BasePtr walking through Ty toward
|
|
/// TargetTy without changing the offset of the pointer.
|
|
///
|
|
/// This routine assumes we've already established a properly offset GEP with
|
|
/// Indices, and arrived at the Ty type. The goal is to continue to GEP with
|
|
/// zero-indices down through type layers until we find one the same as
|
|
/// TargetTy. If we can't find one with the same type, we at least try to use
|
|
/// one with the same size. If none of that works, we just produce the GEP as
|
|
/// indicated by Indices to have the correct offset.
|
|
static Value *getNaturalGEPWithType(IRBuilder<> &IRB, const TargetData &TD,
|
|
Value *BasePtr, Type *Ty, Type *TargetTy,
|
|
SmallVectorImpl<Value *> &Indices,
|
|
const Twine &Prefix) {
|
|
if (Ty == TargetTy)
|
|
return buildGEP(IRB, BasePtr, Indices, Prefix);
|
|
|
|
// See if we can descend into a struct and locate a field with the correct
|
|
// type.
|
|
unsigned NumLayers = 0;
|
|
Type *ElementTy = Ty;
|
|
do {
|
|
if (ElementTy->isPointerTy())
|
|
break;
|
|
if (SequentialType *SeqTy = dyn_cast<SequentialType>(ElementTy)) {
|
|
ElementTy = SeqTy->getElementType();
|
|
Indices.push_back(IRB.getInt(APInt(TD.getPointerSizeInBits(), 0)));
|
|
} else if (StructType *STy = dyn_cast<StructType>(ElementTy)) {
|
|
ElementTy = *STy->element_begin();
|
|
Indices.push_back(IRB.getInt32(0));
|
|
} else {
|
|
break;
|
|
}
|
|
++NumLayers;
|
|
} while (ElementTy != TargetTy);
|
|
if (ElementTy != TargetTy)
|
|
Indices.erase(Indices.end() - NumLayers, Indices.end());
|
|
|
|
return buildGEP(IRB, BasePtr, Indices, Prefix);
|
|
}
|
|
|
|
/// \brief Recursively compute indices for a natural GEP.
|
|
///
|
|
/// This is the recursive step for getNaturalGEPWithOffset that walks down the
|
|
/// element types adding appropriate indices for the GEP.
|
|
static Value *getNaturalGEPRecursively(IRBuilder<> &IRB, const TargetData &TD,
|
|
Value *Ptr, Type *Ty, APInt &Offset,
|
|
Type *TargetTy,
|
|
SmallVectorImpl<Value *> &Indices,
|
|
const Twine &Prefix) {
|
|
if (Offset == 0)
|
|
return getNaturalGEPWithType(IRB, TD, Ptr, Ty, TargetTy, Indices, Prefix);
|
|
|
|
// We can't recurse through pointer types.
|
|
if (Ty->isPointerTy())
|
|
return 0;
|
|
|
|
// We try to analyze GEPs over vectors here, but note that these GEPs are
|
|
// extremely poorly defined currently. The long-term goal is to remove GEPing
|
|
// over a vector from the IR completely.
|
|
if (VectorType *VecTy = dyn_cast<VectorType>(Ty)) {
|
|
unsigned ElementSizeInBits = VecTy->getScalarSizeInBits();
|
|
if (ElementSizeInBits % 8)
|
|
return 0; // GEPs over non-multiple of 8 size vector elements are invalid.
|
|
APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8);
|
|
APInt NumSkippedElements = Offset.udiv(ElementSize);
|
|
if (NumSkippedElements.ugt(VecTy->getNumElements()))
|
|
return 0;
|
|
Offset -= NumSkippedElements * ElementSize;
|
|
Indices.push_back(IRB.getInt(NumSkippedElements));
|
|
return getNaturalGEPRecursively(IRB, TD, Ptr, VecTy->getElementType(),
|
|
Offset, TargetTy, Indices, Prefix);
|
|
}
|
|
|
|
if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
|
|
Type *ElementTy = ArrTy->getElementType();
|
|
APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
|
|
APInt NumSkippedElements = Offset.udiv(ElementSize);
|
|
if (NumSkippedElements.ugt(ArrTy->getNumElements()))
|
|
return 0;
|
|
|
|
Offset -= NumSkippedElements * ElementSize;
|
|
Indices.push_back(IRB.getInt(NumSkippedElements));
|
|
return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
|
|
Indices, Prefix);
|
|
}
|
|
|
|
StructType *STy = dyn_cast<StructType>(Ty);
|
|
if (!STy)
|
|
return 0;
|
|
|
|
const StructLayout *SL = TD.getStructLayout(STy);
|
|
uint64_t StructOffset = Offset.getZExtValue();
|
|
if (StructOffset >= SL->getSizeInBytes())
|
|
return 0;
|
|
unsigned Index = SL->getElementContainingOffset(StructOffset);
|
|
Offset -= APInt(Offset.getBitWidth(), SL->getElementOffset(Index));
|
|
Type *ElementTy = STy->getElementType(Index);
|
|
if (Offset.uge(TD.getTypeAllocSize(ElementTy)))
|
|
return 0; // The offset points into alignment padding.
|
|
|
|
Indices.push_back(IRB.getInt32(Index));
|
|
return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
|
|
Indices, Prefix);
|
|
}
|
|
|
|
/// \brief Get a natural GEP from a base pointer to a particular offset and
|
|
/// resulting in a particular type.
|
|
///
|
|
/// The goal is to produce a "natural" looking GEP that works with the existing
|
|
/// composite types to arrive at the appropriate offset and element type for
|
|
/// a pointer. TargetTy is the element type the returned GEP should point-to if
|
|
/// possible. We recurse by decreasing Offset, adding the appropriate index to
|
|
/// Indices, and setting Ty to the result subtype.
|
|
///
|
|
/// If no natural GEP can be constructed, this function returns null.
|
|
static Value *getNaturalGEPWithOffset(IRBuilder<> &IRB, const TargetData &TD,
|
|
Value *Ptr, APInt Offset, Type *TargetTy,
|
|
SmallVectorImpl<Value *> &Indices,
|
|
const Twine &Prefix) {
|
|
PointerType *Ty = cast<PointerType>(Ptr->getType());
|
|
|
|
// Don't consider any GEPs through an i8* as natural unless the TargetTy is
|
|
// an i8.
|
|
if (Ty == IRB.getInt8PtrTy() && TargetTy->isIntegerTy(8))
|
|
return 0;
|
|
|
|
Type *ElementTy = Ty->getElementType();
|
|
APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
|
|
if (ElementSize == 0)
|
|
return 0; // Zero-length arrays can't help us build a natural GEP.
|
|
APInt NumSkippedElements = Offset.udiv(ElementSize);
|
|
|
|
Offset -= NumSkippedElements * ElementSize;
|
|
Indices.push_back(IRB.getInt(NumSkippedElements));
|
|
return getNaturalGEPRecursively(IRB, TD, Ptr, ElementTy, Offset, TargetTy,
|
|
Indices, Prefix);
|
|
}
|
|
|
|
/// \brief Compute an adjusted pointer from Ptr by Offset bytes where the
|
|
/// resulting pointer has PointerTy.
|
|
///
|
|
/// This tries very hard to compute a "natural" GEP which arrives at the offset
|
|
/// and produces the pointer type desired. Where it cannot, it will try to use
|
|
/// the natural GEP to arrive at the offset and bitcast to the type. Where that
|
|
/// fails, it will try to use an existing i8* and GEP to the byte offset and
|
|
/// bitcast to the type.
|
|
///
|
|
/// The strategy for finding the more natural GEPs is to peel off layers of the
|
|
/// pointer, walking back through bit casts and GEPs, searching for a base
|
|
/// pointer from which we can compute a natural GEP with the desired
|
|
/// properities. The algorithm tries to fold as many constant indices into
|
|
/// a single GEP as possible, thus making each GEP more independent of the
|
|
/// surrounding code.
|
|
static Value *getAdjustedPtr(IRBuilder<> &IRB, const TargetData &TD,
|
|
Value *Ptr, APInt Offset, Type *PointerTy,
|
|
const Twine &Prefix) {
|
|
// Even though we don't look through PHI nodes, we could be called on an
|
|
// instruction in an unreachable block, which may be on a cycle.
|
|
SmallPtrSet<Value *, 4> Visited;
|
|
Visited.insert(Ptr);
|
|
SmallVector<Value *, 4> Indices;
|
|
|
|
// We may end up computing an offset pointer that has the wrong type. If we
|
|
// never are able to compute one directly that has the correct type, we'll
|
|
// fall back to it, so keep it around here.
|
|
Value *OffsetPtr = 0;
|
|
|
|
// Remember any i8 pointer we come across to re-use if we need to do a raw
|
|
// byte offset.
|
|
Value *Int8Ptr = 0;
|
|
APInt Int8PtrOffset(Offset.getBitWidth(), 0);
|
|
|
|
Type *TargetTy = PointerTy->getPointerElementType();
|
|
|
|
do {
|
|
// First fold any existing GEPs into the offset.
|
|
while (GEPOperator *GEP = dyn_cast<GEPOperator>(Ptr)) {
|
|
APInt GEPOffset(Offset.getBitWidth(), 0);
|
|
if (!accumulateGEPOffsets(TD, *GEP, GEPOffset))
|
|
break;
|
|
Offset += GEPOffset;
|
|
Ptr = GEP->getPointerOperand();
|
|
if (!Visited.insert(Ptr))
|
|
break;
|
|
}
|
|
|
|
// See if we can perform a natural GEP here.
|
|
Indices.clear();
|
|
if (Value *P = getNaturalGEPWithOffset(IRB, TD, Ptr, Offset, TargetTy,
|
|
Indices, Prefix)) {
|
|
if (P->getType() == PointerTy) {
|
|
// Zap any offset pointer that we ended up computing in previous rounds.
|
|
if (OffsetPtr && OffsetPtr->use_empty())
|
|
if (Instruction *I = dyn_cast<Instruction>(OffsetPtr))
|
|
I->eraseFromParent();
|
|
return P;
|
|
}
|
|
if (!OffsetPtr) {
|
|
OffsetPtr = P;
|
|
}
|
|
}
|
|
|
|
// Stash this pointer if we've found an i8*.
|
|
if (Ptr->getType()->isIntegerTy(8)) {
|
|
Int8Ptr = Ptr;
|
|
Int8PtrOffset = Offset;
|
|
}
|
|
|
|
// Peel off a layer of the pointer and update the offset appropriately.
|
|
if (Operator::getOpcode(Ptr) == Instruction::BitCast) {
|
|
Ptr = cast<Operator>(Ptr)->getOperand(0);
|
|
} else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(Ptr)) {
|
|
if (GA->mayBeOverridden())
|
|
break;
|
|
Ptr = GA->getAliasee();
|
|
} else {
|
|
break;
|
|
}
|
|
assert(Ptr->getType()->isPointerTy() && "Unexpected operand type!");
|
|
} while (Visited.insert(Ptr));
|
|
|
|
if (!OffsetPtr) {
|
|
if (!Int8Ptr) {
|
|
Int8Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy(),
|
|
Prefix + ".raw_cast");
|
|
Int8PtrOffset = Offset;
|
|
}
|
|
|
|
OffsetPtr = Int8PtrOffset == 0 ? Int8Ptr :
|
|
IRB.CreateInBoundsGEP(Int8Ptr, IRB.getInt(Int8PtrOffset),
|
|
Prefix + ".raw_idx");
|
|
}
|
|
Ptr = OffsetPtr;
|
|
|
|
// On the off chance we were targeting i8*, guard the bitcast here.
|
|
if (Ptr->getType() != PointerTy)
|
|
Ptr = IRB.CreateBitCast(Ptr, PointerTy, Prefix + ".cast");
|
|
|
|
return Ptr;
|
|
}
|
|
|
|
/// \brief Test whether the given alloca partition can be promoted to a vector.
|
|
///
|
|
/// This is a quick test to check whether we can rewrite a particular alloca
|
|
/// partition (and its newly formed alloca) into a vector alloca with only
|
|
/// whole-vector loads and stores such that it could be promoted to a vector
|
|
/// SSA value. We only can ensure this for a limited set of operations, and we
|
|
/// don't want to do the rewrites unless we are confident that the result will
|
|
/// be promotable, so we have an early test here.
|
|
static bool isVectorPromotionViable(const TargetData &TD,
|
|
Type *AllocaTy,
|
|
AllocaPartitioning &P,
|
|
uint64_t PartitionBeginOffset,
|
|
uint64_t PartitionEndOffset,
|
|
AllocaPartitioning::const_use_iterator I,
|
|
AllocaPartitioning::const_use_iterator E) {
|
|
VectorType *Ty = dyn_cast<VectorType>(AllocaTy);
|
|
if (!Ty)
|
|
return false;
|
|
|
|
uint64_t VecSize = TD.getTypeSizeInBits(Ty);
|
|
uint64_t ElementSize = Ty->getScalarSizeInBits();
|
|
|
|
// While the definition of LLVM vectors is bitpacked, we don't support sizes
|
|
// that aren't byte sized.
|
|
if (ElementSize % 8)
|
|
return false;
|
|
assert((VecSize % 8) == 0 && "vector size not a multiple of element size?");
|
|
VecSize /= 8;
|
|
ElementSize /= 8;
|
|
|
|
for (; I != E; ++I) {
|
|
uint64_t BeginOffset = I->BeginOffset - PartitionBeginOffset;
|
|
uint64_t BeginIndex = BeginOffset / ElementSize;
|
|
if (BeginIndex * ElementSize != BeginOffset ||
|
|
BeginIndex >= Ty->getNumElements())
|
|
return false;
|
|
uint64_t EndOffset = I->EndOffset - PartitionBeginOffset;
|
|
uint64_t EndIndex = EndOffset / ElementSize;
|
|
if (EndIndex * ElementSize != EndOffset ||
|
|
EndIndex > Ty->getNumElements())
|
|
return false;
|
|
|
|
// FIXME: We should build shuffle vector instructions to handle
|
|
// non-element-sized accesses.
|
|
if ((EndOffset - BeginOffset) != ElementSize &&
|
|
(EndOffset - BeginOffset) != VecSize)
|
|
return false;
|
|
|
|
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(&*I->User)) {
|
|
if (MI->isVolatile())
|
|
return false;
|
|
if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(&*I->User)) {
|
|
const AllocaPartitioning::MemTransferOffsets &MTO
|
|
= P.getMemTransferOffsets(*MTI);
|
|
if (!MTO.IsSplittable)
|
|
return false;
|
|
}
|
|
} else if (I->Ptr->getType()->getPointerElementType()->isStructTy()) {
|
|
// Disable vector promotion when there are loads or stores of an FCA.
|
|
return false;
|
|
} else if (!isa<LoadInst>(*I->User) && !isa<StoreInst>(*I->User)) {
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
namespace {
|
|
/// \brief Visitor to rewrite instructions using a partition of an alloca to
|
|
/// use a new alloca.
|
|
///
|
|
/// Also implements the rewriting to vector-based accesses when the partition
|
|
/// passes the isVectorPromotionViable predicate. Most of the rewriting logic
|
|
/// lives here.
|
|
class AllocaPartitionRewriter : public InstVisitor<AllocaPartitionRewriter,
|
|
bool> {
|
|
// Befriend the base class so it can delegate to private visit methods.
|
|
friend class llvm::InstVisitor<AllocaPartitionRewriter, bool>;
|
|
|
|
const TargetData &TD;
|
|
AllocaPartitioning &P;
|
|
SROA &Pass;
|
|
AllocaInst &OldAI, &NewAI;
|
|
const uint64_t NewAllocaBeginOffset, NewAllocaEndOffset;
|
|
|
|
// If we are rewriting an alloca partition which can be written as pure
|
|
// vector operations, we stash extra information here. When VecTy is
|
|
// non-null, we have some strict guarantees about the rewriten alloca:
|
|
// - The new alloca is exactly the size of the vector type here.
|
|
// - The accesses all either map to the entire vector or to a single
|
|
// element.
|
|
// - The set of accessing instructions is only one of those handled above
|
|
// in isVectorPromotionViable. Generally these are the same access kinds
|
|
// which are promotable via mem2reg.
|
|
VectorType *VecTy;
|
|
Type *ElementTy;
|
|
uint64_t ElementSize;
|
|
|
|
// The offset of the partition user currently being rewritten.
|
|
uint64_t BeginOffset, EndOffset;
|
|
Instruction *OldPtr;
|
|
|
|
// The name prefix to use when rewriting instructions for this alloca.
|
|
std::string NamePrefix;
|
|
|
|
public:
|
|
AllocaPartitionRewriter(const TargetData &TD, AllocaPartitioning &P,
|
|
AllocaPartitioning::iterator PI,
|
|
SROA &Pass, AllocaInst &OldAI, AllocaInst &NewAI,
|
|
uint64_t NewBeginOffset, uint64_t NewEndOffset)
|
|
: TD(TD), P(P), Pass(Pass),
|
|
OldAI(OldAI), NewAI(NewAI),
|
|
NewAllocaBeginOffset(NewBeginOffset),
|
|
NewAllocaEndOffset(NewEndOffset),
|
|
VecTy(), ElementTy(), ElementSize(),
|
|
BeginOffset(), EndOffset() {
|
|
}
|
|
|
|
/// \brief Visit the users of the alloca partition and rewrite them.
|
|
bool visitUsers(AllocaPartitioning::const_use_iterator I,
|
|
AllocaPartitioning::const_use_iterator E) {
|
|
if (isVectorPromotionViable(TD, NewAI.getAllocatedType(), P,
|
|
NewAllocaBeginOffset, NewAllocaEndOffset,
|
|
I, E)) {
|
|
++NumVectorized;
|
|
VecTy = cast<VectorType>(NewAI.getAllocatedType());
|
|
ElementTy = VecTy->getElementType();
|
|
assert((VecTy->getScalarSizeInBits() % 8) == 0 &&
|
|
"Only multiple-of-8 sized vector elements are viable");
|
|
ElementSize = VecTy->getScalarSizeInBits() / 8;
|
|
}
|
|
bool CanSROA = true;
|
|
for (; I != E; ++I) {
|
|
BeginOffset = I->BeginOffset;
|
|
EndOffset = I->EndOffset;
|
|
OldPtr = I->Ptr;
|
|
NamePrefix = (Twine(NewAI.getName()) + "." + Twine(BeginOffset)).str();
|
|
CanSROA &= visit(I->User);
|
|
}
|
|
if (VecTy) {
|
|
assert(CanSROA);
|
|
VecTy = 0;
|
|
ElementTy = 0;
|
|
ElementSize = 0;
|
|
}
|
|
return CanSROA;
|
|
}
|
|
|
|
private:
|
|
// Every instruction which can end up as a user must have a rewrite rule.
|
|
bool visitInstruction(Instruction &I) {
|
|
DEBUG(dbgs() << " !!!! Cannot rewrite: " << I << "\n");
|
|
llvm_unreachable("No rewrite rule for this instruction!");
|
|
}
|
|
|
|
Twine getName(const Twine &Suffix) {
|
|
return NamePrefix + Suffix;
|
|
}
|
|
|
|
Value *getAdjustedAllocaPtr(IRBuilder<> &IRB, Type *PointerTy) {
|
|
assert(BeginOffset >= NewAllocaBeginOffset);
|
|
APInt Offset(TD.getPointerSizeInBits(), BeginOffset - NewAllocaBeginOffset);
|
|
return getAdjustedPtr(IRB, TD, &NewAI, Offset, PointerTy, getName(""));
|
|
}
|
|
|
|
ConstantInt *getIndex(IRBuilder<> &IRB, uint64_t Offset) {
|
|
assert(VecTy && "Can only call getIndex when rewriting a vector");
|
|
uint64_t RelOffset = Offset - NewAllocaBeginOffset;
|
|
assert(RelOffset / ElementSize < UINT32_MAX && "Index out of bounds");
|
|
uint32_t Index = RelOffset / ElementSize;
|
|
assert(Index * ElementSize == RelOffset);
|
|
return IRB.getInt32(Index);
|
|
}
|
|
|
|
void deleteIfTriviallyDead(Value *V) {
|
|
Instruction *I = cast<Instruction>(V);
|
|
if (isInstructionTriviallyDead(I))
|
|
Pass.DeadInsts.push_back(I);
|
|
}
|
|
|
|
Value *getValueCast(IRBuilder<> &IRB, Value *V, Type *Ty) {
|
|
if (V->getType()->isIntegerTy() && Ty->isPointerTy())
|
|
return IRB.CreateIntToPtr(V, Ty);
|
|
if (V->getType()->isPointerTy() && Ty->isIntegerTy())
|
|
return IRB.CreatePtrToInt(V, Ty);
|
|
|
|
return IRB.CreateBitCast(V, Ty);
|
|
}
|
|
|
|
bool rewriteVectorizedLoadInst(IRBuilder<> &IRB, LoadInst &LI, Value *OldOp) {
|
|
Value *Result;
|
|
if (LI.getType() == VecTy->getElementType() ||
|
|
BeginOffset > NewAllocaBeginOffset || EndOffset < NewAllocaEndOffset) {
|
|
Result
|
|
= IRB.CreateExtractElement(IRB.CreateLoad(&NewAI, getName(".load")),
|
|
getIndex(IRB, BeginOffset),
|
|
getName(".extract"));
|
|
} else {
|
|
Result = IRB.CreateLoad(&NewAI, getName(".load"));
|
|
}
|
|
if (Result->getType() != LI.getType())
|
|
Result = getValueCast(IRB, Result, LI.getType());
|
|
LI.replaceAllUsesWith(Result);
|
|
Pass.DeadInsts.push_back(&LI);
|
|
|
|
DEBUG(dbgs() << " to: " << *Result << "\n");
|
|
return true;
|
|
}
|
|
|
|
bool visitLoadInst(LoadInst &LI) {
|
|
DEBUG(dbgs() << " original: " << LI << "\n");
|
|
Value *OldOp = LI.getOperand(0);
|
|
assert(OldOp == OldPtr);
|
|
IRBuilder<> IRB(&LI);
|
|
|
|
if (VecTy)
|
|
return rewriteVectorizedLoadInst(IRB, LI, OldOp);
|
|
|
|
Value *NewPtr = getAdjustedAllocaPtr(IRB,
|
|
LI.getPointerOperand()->getType());
|
|
LI.setOperand(0, NewPtr);
|
|
DEBUG(dbgs() << " to: " << LI << "\n");
|
|
|
|
deleteIfTriviallyDead(OldOp);
|
|
return NewPtr == &NewAI && !LI.isVolatile();
|
|
}
|
|
|
|
bool rewriteVectorizedStoreInst(IRBuilder<> &IRB, StoreInst &SI,
|
|
Value *OldOp) {
|
|
Value *V = SI.getValueOperand();
|
|
if (V->getType() == ElementTy ||
|
|
BeginOffset > NewAllocaBeginOffset || EndOffset < NewAllocaEndOffset) {
|
|
if (V->getType() != ElementTy)
|
|
V = getValueCast(IRB, V, ElementTy);
|
|
V = IRB.CreateInsertElement(IRB.CreateLoad(&NewAI, getName(".load")), V,
|
|
getIndex(IRB, BeginOffset),
|
|
getName(".insert"));
|
|
} else if (V->getType() != VecTy) {
|
|
V = getValueCast(IRB, V, VecTy);
|
|
}
|
|
StoreInst *Store = IRB.CreateStore(V, &NewAI);
|
|
Pass.DeadInsts.push_back(&SI);
|
|
|
|
(void)Store;
|
|
DEBUG(dbgs() << " to: " << *Store << "\n");
|
|
return true;
|
|
}
|
|
|
|
bool visitStoreInst(StoreInst &SI) {
|
|
DEBUG(dbgs() << " original: " << SI << "\n");
|
|
Value *OldOp = SI.getOperand(1);
|
|
assert(OldOp == OldPtr);
|
|
IRBuilder<> IRB(&SI);
|
|
|
|
if (VecTy)
|
|
return rewriteVectorizedStoreInst(IRB, SI, OldOp);
|
|
|
|
Value *NewPtr = getAdjustedAllocaPtr(IRB,
|
|
SI.getPointerOperand()->getType());
|
|
SI.setOperand(1, NewPtr);
|
|
DEBUG(dbgs() << " to: " << SI << "\n");
|
|
|
|
deleteIfTriviallyDead(OldOp);
|
|
return NewPtr == &NewAI && !SI.isVolatile();
|
|
}
|
|
|
|
bool visitMemSetInst(MemSetInst &II) {
|
|
DEBUG(dbgs() << " original: " << II << "\n");
|
|
IRBuilder<> IRB(&II);
|
|
assert(II.getRawDest() == OldPtr);
|
|
|
|
// If the memset has a variable size, it cannot be split, just adjust the
|
|
// pointer to the new alloca.
|
|
if (!isa<Constant>(II.getLength())) {
|
|
II.setDest(getAdjustedAllocaPtr(IRB, II.getRawDest()->getType()));
|
|
deleteIfTriviallyDead(OldPtr);
|
|
return false;
|
|
}
|
|
|
|
// Record this instruction for deletion.
|
|
if (Pass.DeadSplitInsts.insert(&II))
|
|
Pass.DeadInsts.push_back(&II);
|
|
|
|
Type *AllocaTy = NewAI.getAllocatedType();
|
|
Type *ScalarTy = AllocaTy->getScalarType();
|
|
|
|
// If this doesn't map cleanly onto the alloca type, and that type isn't
|
|
// a single value type, just emit a memset.
|
|
if (!VecTy && (BeginOffset != NewAllocaBeginOffset ||
|
|
EndOffset != NewAllocaEndOffset ||
|
|
!AllocaTy->isSingleValueType() ||
|
|
!TD.isLegalInteger(TD.getTypeSizeInBits(ScalarTy)))) {
|
|
Type *SizeTy = II.getLength()->getType();
|
|
Constant *Size = ConstantInt::get(SizeTy, EndOffset - BeginOffset);
|
|
|
|
CallInst *New
|
|
= IRB.CreateMemSet(getAdjustedAllocaPtr(IRB,
|
|
II.getRawDest()->getType()),
|
|
II.getValue(), Size, II.getAlignment(),
|
|
II.isVolatile());
|
|
(void)New;
|
|
DEBUG(dbgs() << " to: " << *New << "\n");
|
|
return false;
|
|
}
|
|
|
|
// If we can represent this as a simple value, we have to build the actual
|
|
// value to store, which requires expanding the byte present in memset to
|
|
// a sensible representation for the alloca type. This is essentially
|
|
// splatting the byte to a sufficiently wide integer, bitcasting to the
|
|
// desired scalar type, and splatting it across any desired vector type.
|
|
Value *V = II.getValue();
|
|
IntegerType *VTy = cast<IntegerType>(V->getType());
|
|
Type *IntTy = Type::getIntNTy(VTy->getContext(),
|
|
TD.getTypeSizeInBits(ScalarTy));
|
|
if (TD.getTypeSizeInBits(ScalarTy) > VTy->getBitWidth())
|
|
V = IRB.CreateMul(IRB.CreateZExt(V, IntTy, getName(".zext")),
|
|
ConstantExpr::getUDiv(
|
|
Constant::getAllOnesValue(IntTy),
|
|
ConstantExpr::getZExt(
|
|
Constant::getAllOnesValue(V->getType()),
|
|
IntTy)),
|
|
getName(".isplat"));
|
|
if (V->getType() != ScalarTy) {
|
|
if (ScalarTy->isPointerTy())
|
|
V = IRB.CreateIntToPtr(V, ScalarTy);
|
|
else if (ScalarTy->isPrimitiveType() || ScalarTy->isVectorTy())
|
|
V = IRB.CreateBitCast(V, ScalarTy);
|
|
else if (ScalarTy->isIntegerTy())
|
|
llvm_unreachable("Computed different integer types with equal widths");
|
|
else
|
|
llvm_unreachable("Invalid scalar type");
|
|
}
|
|
|
|
// If this is an element-wide memset of a vectorizable alloca, insert it.
|
|
if (VecTy && (BeginOffset > NewAllocaBeginOffset ||
|
|
EndOffset < NewAllocaEndOffset)) {
|
|
StoreInst *Store = IRB.CreateStore(
|
|
IRB.CreateInsertElement(IRB.CreateLoad(&NewAI, getName(".load")), V,
|
|
getIndex(IRB, BeginOffset),
|
|
getName(".insert")),
|
|
&NewAI);
|
|
(void)Store;
|
|
DEBUG(dbgs() << " to: " << *Store << "\n");
|
|
return true;
|
|
}
|
|
|
|
// Splat to a vector if needed.
|
|
if (VectorType *VecTy = dyn_cast<VectorType>(AllocaTy)) {
|
|
VectorType *SplatSourceTy = VectorType::get(V->getType(), 1);
|
|
V = IRB.CreateShuffleVector(
|
|
IRB.CreateInsertElement(UndefValue::get(SplatSourceTy), V,
|
|
IRB.getInt32(0), getName(".vsplat.insert")),
|
|
UndefValue::get(SplatSourceTy),
|
|
ConstantVector::getSplat(VecTy->getNumElements(), IRB.getInt32(0)),
|
|
getName(".vsplat.shuffle"));
|
|
assert(V->getType() == VecTy);
|
|
}
|
|
|
|
Value *New = IRB.CreateStore(V, &NewAI, II.isVolatile());
|
|
(void)New;
|
|
DEBUG(dbgs() << " to: " << *New << "\n");
|
|
return !II.isVolatile();
|
|
}
|
|
|
|
bool visitMemTransferInst(MemTransferInst &II) {
|
|
// Rewriting of memory transfer instructions can be a bit tricky. We break
|
|
// them into two categories: split intrinsics and unsplit intrinsics.
|
|
|
|
DEBUG(dbgs() << " original: " << II << "\n");
|
|
IRBuilder<> IRB(&II);
|
|
|
|
assert(II.getRawSource() == OldPtr || II.getRawDest() == OldPtr);
|
|
bool IsDest = II.getRawDest() == OldPtr;
|
|
|
|
const AllocaPartitioning::MemTransferOffsets &MTO
|
|
= P.getMemTransferOffsets(II);
|
|
|
|
// For unsplit intrinsics, we simply modify the source and destination
|
|
// pointers in place. This isn't just an optimization, it is a matter of
|
|
// correctness. With unsplit intrinsics we may be dealing with transfers
|
|
// within a single alloca before SROA ran, or with transfers that have
|
|
// a variable length. We may also be dealing with memmove instead of
|
|
// memcpy, and so simply updating the pointers is the necessary for us to
|
|
// update both source and dest of a single call.
|
|
if (!MTO.IsSplittable) {
|
|
Value *OldOp = IsDest ? II.getRawDest() : II.getRawSource();
|
|
if (IsDest)
|
|
II.setDest(getAdjustedAllocaPtr(IRB, II.getRawDest()->getType()));
|
|
else
|
|
II.setSource(getAdjustedAllocaPtr(IRB, II.getRawSource()->getType()));
|
|
|
|
DEBUG(dbgs() << " to: " << II << "\n");
|
|
deleteIfTriviallyDead(OldOp);
|
|
return false;
|
|
}
|
|
// For split transfer intrinsics we have an incredibly useful assurance:
|
|
// the source and destination do not reside within the same alloca, and at
|
|
// least one of them does not escape. This means that we can replace
|
|
// memmove with memcpy, and we don't need to worry about all manner of
|
|
// downsides to splitting and transforming the operations.
|
|
|
|
// Compute the relative offset within the transfer.
|
|
unsigned IntPtrWidth = TD.getPointerSizeInBits();
|
|
APInt RelOffset(IntPtrWidth, BeginOffset - (IsDest ? MTO.DestBegin
|
|
: MTO.SourceBegin));
|
|
|
|
// If this doesn't map cleanly onto the alloca type, and that type isn't
|
|
// a single value type, just emit a memcpy.
|
|
bool EmitMemCpy
|
|
= !VecTy && (BeginOffset != NewAllocaBeginOffset ||
|
|
EndOffset != NewAllocaEndOffset ||
|
|
!NewAI.getAllocatedType()->isSingleValueType());
|
|
|
|
// If we're just going to emit a memcpy, the alloca hasn't changed, and the
|
|
// size hasn't been shrunk based on analysis of the viable range, this is
|
|
// a no-op.
|
|
if (EmitMemCpy && &OldAI == &NewAI) {
|
|
uint64_t OrigBegin = IsDest ? MTO.DestBegin : MTO.SourceBegin;
|
|
uint64_t OrigEnd = IsDest ? MTO.DestEnd : MTO.SourceEnd;
|
|
// Ensure the start lines up.
|
|
assert(BeginOffset == OrigBegin);
|
|
(void)OrigBegin;
|
|
|
|
// Rewrite the size as needed.
|
|
if (EndOffset != OrigEnd)
|
|
II.setLength(ConstantInt::get(II.getLength()->getType(),
|
|
EndOffset - BeginOffset));
|
|
return false;
|
|
}
|
|
// Record this instruction for deletion.
|
|
if (Pass.DeadSplitInsts.insert(&II))
|
|
Pass.DeadInsts.push_back(&II);
|
|
|
|
bool IsVectorElement = VecTy && (BeginOffset > NewAllocaBeginOffset ||
|
|
EndOffset < NewAllocaEndOffset);
|
|
|
|
Type *OtherPtrTy = IsDest ? II.getRawSource()->getType()
|
|
: II.getRawDest()->getType();
|
|
if (!EmitMemCpy)
|
|
OtherPtrTy = IsVectorElement ? VecTy->getElementType()->getPointerTo()
|
|
: NewAI.getType();
|
|
|
|
// Compute the other pointer, folding as much as possible to produce
|
|
// a single, simple GEP in most cases.
|
|
Value *OtherPtr = IsDest ? II.getRawSource() : II.getRawDest();
|
|
OtherPtr = getAdjustedPtr(IRB, TD, OtherPtr, RelOffset, OtherPtrTy,
|
|
getName("." + OtherPtr->getName()));
|
|
|
|
// Strip all inbounds GEPs and pointer casts to try to dig out any root
|
|
// alloca that should be re-examined after rewriting this instruction.
|
|
if (AllocaInst *AI
|
|
= dyn_cast<AllocaInst>(OtherPtr->stripInBoundsOffsets()))
|
|
Pass.Worklist.insert(AI);
|
|
|
|
if (EmitMemCpy) {
|
|
Value *OurPtr
|
|
= getAdjustedAllocaPtr(IRB, IsDest ? II.getRawDest()->getType()
|
|
: II.getRawSource()->getType());
|
|
Type *SizeTy = II.getLength()->getType();
|
|
Constant *Size = ConstantInt::get(SizeTy, EndOffset - BeginOffset);
|
|
|
|
CallInst *New = IRB.CreateMemCpy(IsDest ? OurPtr : OtherPtr,
|
|
IsDest ? OtherPtr : OurPtr,
|
|
Size, II.getAlignment(),
|
|
II.isVolatile());
|
|
(void)New;
|
|
DEBUG(dbgs() << " to: " << *New << "\n");
|
|
return false;
|
|
}
|
|
|
|
Value *SrcPtr = OtherPtr;
|
|
Value *DstPtr = &NewAI;
|
|
if (!IsDest)
|
|
std::swap(SrcPtr, DstPtr);
|
|
|
|
Value *Src;
|
|
if (IsVectorElement && !IsDest) {
|
|
// We have to extract rather than load.
|
|
Src = IRB.CreateExtractElement(IRB.CreateLoad(SrcPtr,
|
|
getName(".copyload")),
|
|
getIndex(IRB, BeginOffset),
|
|
getName(".copyextract"));
|
|
} else {
|
|
Src = IRB.CreateLoad(SrcPtr, II.isVolatile(), getName(".copyload"));
|
|
}
|
|
|
|
if (IsVectorElement && IsDest) {
|
|
// We have to insert into a loaded copy before storing.
|
|
Src = IRB.CreateInsertElement(IRB.CreateLoad(&NewAI, getName(".load")),
|
|
Src, getIndex(IRB, BeginOffset),
|
|
getName(".insert"));
|
|
}
|
|
|
|
Value *Store = IRB.CreateStore(Src, DstPtr, II.isVolatile());
|
|
(void)Store;
|
|
DEBUG(dbgs() << " to: " << *Store << "\n");
|
|
return !II.isVolatile();
|
|
}
|
|
|
|
bool visitIntrinsicInst(IntrinsicInst &II) {
|
|
assert(II.getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II.getIntrinsicID() == Intrinsic::lifetime_end);
|
|
DEBUG(dbgs() << " original: " << II << "\n");
|
|
IRBuilder<> IRB(&II);
|
|
assert(II.getArgOperand(1) == OldPtr);
|
|
|
|
// Record this instruction for deletion.
|
|
if (Pass.DeadSplitInsts.insert(&II))
|
|
Pass.DeadInsts.push_back(&II);
|
|
|
|
ConstantInt *Size
|
|
= ConstantInt::get(cast<IntegerType>(II.getArgOperand(0)->getType()),
|
|
EndOffset - BeginOffset);
|
|
Value *Ptr = getAdjustedAllocaPtr(IRB, II.getArgOperand(1)->getType());
|
|
Value *New;
|
|
if (II.getIntrinsicID() == Intrinsic::lifetime_start)
|
|
New = IRB.CreateLifetimeStart(Ptr, Size);
|
|
else
|
|
New = IRB.CreateLifetimeEnd(Ptr, Size);
|
|
|
|
DEBUG(dbgs() << " to: " << *New << "\n");
|
|
return true;
|
|
}
|
|
|
|
/// PHI instructions that use an alloca and are subsequently loaded can be
|
|
/// rewritten to load both input pointers in the pred blocks and then PHI the
|
|
/// results, allowing the load of the alloca to be promoted.
|
|
/// From this:
|
|
/// %P2 = phi [i32* %Alloca, i32* %Other]
|
|
/// %V = load i32* %P2
|
|
/// to:
|
|
/// %V1 = load i32* %Alloca -> will be mem2reg'd
|
|
/// ...
|
|
/// %V2 = load i32* %Other
|
|
/// ...
|
|
/// %V = phi [i32 %V1, i32 %V2]
|
|
///
|
|
/// We can do this to a select if its only uses are loads and if the operand
|
|
/// to the select can be loaded unconditionally.
|
|
///
|
|
/// FIXME: This should be hoisted into a generic utility, likely in
|
|
/// Transforms/Util/Local.h
|
|
bool isSafePHIToSpeculate(PHINode &PN, SmallVectorImpl<LoadInst *> &Loads) {
|
|
// For now, we can only do this promotion if the load is in the same block
|
|
// as the PHI, and if there are no stores between the phi and load.
|
|
// TODO: Allow recursive phi users.
|
|
// TODO: Allow stores.
|
|
BasicBlock *BB = PN.getParent();
|
|
unsigned MaxAlign = 0;
|
|
for (Value::use_iterator UI = PN.use_begin(), UE = PN.use_end();
|
|
UI != UE; ++UI) {
|
|
LoadInst *LI = dyn_cast<LoadInst>(*UI);
|
|
if (LI == 0 || !LI->isSimple()) return false;
|
|
|
|
// For now we only allow loads in the same block as the PHI. This is
|
|
// a common case that happens when instcombine merges two loads through
|
|
// a PHI.
|
|
if (LI->getParent() != BB) return false;
|
|
|
|
// Ensure that there are no instructions between the PHI and the load that
|
|
// could store.
|
|
for (BasicBlock::iterator BBI = &PN; &*BBI != LI; ++BBI)
|
|
if (BBI->mayWriteToMemory())
|
|
return false;
|
|
|
|
MaxAlign = std::max(MaxAlign, LI->getAlignment());
|
|
Loads.push_back(LI);
|
|
}
|
|
|
|
// We can only transform this if it is safe to push the loads into the
|
|
// predecessor blocks. The only thing to watch out for is that we can't put
|
|
// a possibly trapping load in the predecessor if it is a critical edge.
|
|
for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num;
|
|
++Idx) {
|
|
TerminatorInst *TI = PN.getIncomingBlock(Idx)->getTerminator();
|
|
Value *InVal = PN.getIncomingValue(Idx);
|
|
|
|
// If the value is produced by the terminator of the predecessor (an
|
|
// invoke) or it has side-effects, there is no valid place to put a load
|
|
// in the predecessor.
|
|
if (TI == InVal || TI->mayHaveSideEffects())
|
|
return false;
|
|
|
|
// If the predecessor has a single successor, then the edge isn't
|
|
// critical.
|
|
if (TI->getNumSuccessors() == 1)
|
|
continue;
|
|
|
|
// If this pointer is always safe to load, or if we can prove that there
|
|
// is already a load in the block, then we can move the load to the pred
|
|
// block.
|
|
if (InVal->isDereferenceablePointer() ||
|
|
isSafeToLoadUnconditionally(InVal, TI, MaxAlign, &TD))
|
|
continue;
|
|
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
bool visitPHINode(PHINode &PN) {
|
|
DEBUG(dbgs() << " original: " << PN << "\n");
|
|
// We would like to compute a new pointer in only one place, but have it be
|
|
// as local as possible to the PHI. To do that, we re-use the location of
|
|
// the old pointer, which necessarily must be in the right position to
|
|
// dominate the PHI.
|
|
IRBuilder<> PtrBuilder(cast<Instruction>(OldPtr));
|
|
|
|
SmallVector<LoadInst *, 4> Loads;
|
|
if (!isSafePHIToSpeculate(PN, Loads)) {
|
|
Value *NewPtr = getAdjustedAllocaPtr(PtrBuilder, OldPtr->getType());
|
|
// Replace the operands which were using the old pointer.
|
|
User::op_iterator OI = PN.op_begin(), OE = PN.op_end();
|
|
for (; OI != OE; ++OI)
|
|
if (*OI == OldPtr)
|
|
*OI = NewPtr;
|
|
|
|
DEBUG(dbgs() << " to: " << PN << "\n");
|
|
deleteIfTriviallyDead(OldPtr);
|
|
return false;
|
|
}
|
|
assert(!Loads.empty());
|
|
|
|
Type *LoadTy = cast<PointerType>(PN.getType())->getElementType();
|
|
IRBuilder<> PHIBuilder(&PN);
|
|
PHINode *NewPN = PHIBuilder.CreatePHI(LoadTy, PN.getNumIncomingValues());
|
|
NewPN->takeName(&PN);
|
|
|
|
// Get the TBAA tag and alignment to use from one of the loads. It doesn't
|
|
// matter which one we get and if any differ, it doesn't matter.
|
|
LoadInst *SomeLoad = cast<LoadInst>(Loads.back());
|
|
MDNode *TBAATag = SomeLoad->getMetadata(LLVMContext::MD_tbaa);
|
|
unsigned Align = SomeLoad->getAlignment();
|
|
Value *NewPtr = getAdjustedAllocaPtr(PtrBuilder, OldPtr->getType());
|
|
|
|
// Rewrite all loads of the PN to use the new PHI.
|
|
do {
|
|
LoadInst *LI = Loads.pop_back_val();
|
|
LI->replaceAllUsesWith(NewPN);
|
|
Pass.DeadInsts.push_back(LI);
|
|
} while (!Loads.empty());
|
|
|
|
// Inject loads into all of the pred blocks.
|
|
for (unsigned Idx = 0, Num = PN.getNumIncomingValues(); Idx != Num; ++Idx) {
|
|
BasicBlock *Pred = PN.getIncomingBlock(Idx);
|
|
TerminatorInst *TI = Pred->getTerminator();
|
|
Value *InVal = PN.getIncomingValue(Idx);
|
|
IRBuilder<> PredBuilder(TI);
|
|
|
|
// Map the value to the new alloca pointer if this was the old alloca
|
|
// pointer.
|
|
bool ThisOperand = InVal == OldPtr;
|
|
if (ThisOperand)
|
|
InVal = NewPtr;
|
|
|
|
LoadInst *Load
|
|
= PredBuilder.CreateLoad(InVal, getName(".sroa.speculate." +
|
|
Pred->getName()));
|
|
++NumLoadsSpeculated;
|
|
Load->setAlignment(Align);
|
|
if (TBAATag)
|
|
Load->setMetadata(LLVMContext::MD_tbaa, TBAATag);
|
|
NewPN->addIncoming(Load, Pred);
|
|
|
|
if (ThisOperand)
|
|
continue;
|
|
Instruction *OtherPtr = dyn_cast<Instruction>(InVal);
|
|
if (!OtherPtr)
|
|
// No uses to rewrite.
|
|
continue;
|
|
|
|
// Try to lookup and rewrite any partition uses corresponding to this phi
|
|
// input.
|
|
AllocaPartitioning::iterator PI
|
|
= P.findPartitionForPHIOrSelectOperand(PN, OtherPtr);
|
|
if (PI != P.end()) {
|
|
// If the other pointer is within the partitioning, replace the PHI in
|
|
// its uses with the load we just speculated, or add another load for
|
|
// it to rewrite if we've already replaced the PHI.
|
|
AllocaPartitioning::use_iterator UI
|
|
= P.findPartitionUseForPHIOrSelectOperand(PN, OtherPtr);
|
|
if (isa<PHINode>(*UI->User))
|
|
UI->User = Load;
|
|
else {
|
|
AllocaPartitioning::PartitionUse OtherUse = *UI;
|
|
OtherUse.User = Load;
|
|
P.use_insert(PI, std::upper_bound(UI, P.use_end(PI), OtherUse),
|
|
OtherUse);
|
|
}
|
|
}
|
|
}
|
|
DEBUG(dbgs() << " speculated to: " << *NewPN << "\n");
|
|
return NewPtr == &NewAI;
|
|
}
|
|
|
|
/// Select instructions that use an alloca and are subsequently loaded can be
|
|
/// rewritten to load both input pointers and then select between the result,
|
|
/// allowing the load of the alloca to be promoted.
|
|
/// From this:
|
|
/// %P2 = select i1 %cond, i32* %Alloca, i32* %Other
|
|
/// %V = load i32* %P2
|
|
/// to:
|
|
/// %V1 = load i32* %Alloca -> will be mem2reg'd
|
|
/// %V2 = load i32* %Other
|
|
/// %V = select i1 %cond, i32 %V1, i32 %V2
|
|
///
|
|
/// We can do this to a select if its only uses are loads and if the operand
|
|
/// to the select can be loaded unconditionally.
|
|
bool isSafeSelectToSpeculate(SelectInst &SI,
|
|
SmallVectorImpl<LoadInst *> &Loads) {
|
|
Value *TValue = SI.getTrueValue();
|
|
Value *FValue = SI.getFalseValue();
|
|
bool TDerefable = TValue->isDereferenceablePointer();
|
|
bool FDerefable = FValue->isDereferenceablePointer();
|
|
|
|
for (Value::use_iterator UI = SI.use_begin(), UE = SI.use_end();
|
|
UI != UE; ++UI) {
|
|
LoadInst *LI = dyn_cast<LoadInst>(*UI);
|
|
if (LI == 0 || !LI->isSimple()) return false;
|
|
|
|
// Both operands to the select need to be dereferencable, either
|
|
// absolutely (e.g. allocas) or at this point because we can see other
|
|
// accesses to it.
|
|
if (!TDerefable && !isSafeToLoadUnconditionally(TValue, LI,
|
|
LI->getAlignment(), &TD))
|
|
return false;
|
|
if (!FDerefable && !isSafeToLoadUnconditionally(FValue, LI,
|
|
LI->getAlignment(), &TD))
|
|
return false;
|
|
Loads.push_back(LI);
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
bool visitSelectInst(SelectInst &SI) {
|
|
DEBUG(dbgs() << " original: " << SI << "\n");
|
|
IRBuilder<> IRB(&SI);
|
|
|
|
// Find the operand we need to rewrite here.
|
|
bool IsTrueVal = SI.getTrueValue() == OldPtr;
|
|
if (IsTrueVal)
|
|
assert(SI.getFalseValue() != OldPtr && "Pointer is both operands!");
|
|
else
|
|
assert(SI.getFalseValue() == OldPtr && "Pointer isn't an operand!");
|
|
Value *NewPtr = getAdjustedAllocaPtr(IRB, OldPtr->getType());
|
|
|
|
// If the select isn't safe to speculate, just use simple logic to emit it.
|
|
SmallVector<LoadInst *, 4> Loads;
|
|
if (!isSafeSelectToSpeculate(SI, Loads)) {
|
|
SI.setOperand(IsTrueVal ? 1 : 2, NewPtr);
|
|
DEBUG(dbgs() << " to: " << SI << "\n");
|
|
deleteIfTriviallyDead(OldPtr);
|
|
return false;
|
|
}
|
|
|
|
Value *OtherPtr = IsTrueVal ? SI.getFalseValue() : SI.getTrueValue();
|
|
AllocaPartitioning::iterator PI
|
|
= P.findPartitionForPHIOrSelectOperand(SI, OtherPtr);
|
|
AllocaPartitioning::PartitionUse OtherUse;
|
|
if (PI != P.end()) {
|
|
// If the other pointer is within the partitioning, remove the select
|
|
// from its uses. We'll add in the new loads below.
|
|
AllocaPartitioning::use_iterator UI
|
|
= P.findPartitionUseForPHIOrSelectOperand(SI, OtherPtr);
|
|
OtherUse = *UI;
|
|
P.use_erase(PI, UI);
|
|
}
|
|
|
|
Value *TV = IsTrueVal ? NewPtr : SI.getTrueValue();
|
|
Value *FV = IsTrueVal ? SI.getFalseValue() : NewPtr;
|
|
// Replace the loads of the select with a select of two loads.
|
|
while (!Loads.empty()) {
|
|
LoadInst *LI = Loads.pop_back_val();
|
|
|
|
IRB.SetInsertPoint(LI);
|
|
LoadInst *TL =
|
|
IRB.CreateLoad(TV, getName("." + LI->getName() + ".true"));
|
|
LoadInst *FL =
|
|
IRB.CreateLoad(FV, getName("." + LI->getName() + ".false"));
|
|
NumLoadsSpeculated += 2;
|
|
if (PI != P.end()) {
|
|
LoadInst *OtherLoad = IsTrueVal ? FL : TL;
|
|
assert(OtherUse.Ptr == OtherLoad->getOperand(0));
|
|
OtherUse.User = OtherLoad;
|
|
P.use_insert(PI, P.use_end(PI), OtherUse);
|
|
}
|
|
|
|
// Transfer alignment and TBAA info if present.
|
|
TL->setAlignment(LI->getAlignment());
|
|
FL->setAlignment(LI->getAlignment());
|
|
if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa)) {
|
|
TL->setMetadata(LLVMContext::MD_tbaa, Tag);
|
|
FL->setMetadata(LLVMContext::MD_tbaa, Tag);
|
|
}
|
|
|
|
Value *V = IRB.CreateSelect(SI.getCondition(), TL, FL);
|
|
V->takeName(LI);
|
|
DEBUG(dbgs() << " speculated to: " << *V << "\n");
|
|
LI->replaceAllUsesWith(V);
|
|
Pass.DeadInsts.push_back(LI);
|
|
}
|
|
if (PI != P.end())
|
|
std::stable_sort(P.use_begin(PI), P.use_end(PI));
|
|
|
|
deleteIfTriviallyDead(OldPtr);
|
|
return NewPtr == &NewAI;
|
|
}
|
|
|
|
};
|
|
}
|
|
|
|
/// \brief Try to find a partition of the aggregate type passed in for a given
|
|
/// offset and size.
|
|
///
|
|
/// This recurses through the aggregate type and tries to compute a subtype
|
|
/// based on the offset and size. When the offset and size span a sub-section
|
|
/// of an array, it will even compute a new array type for that sub-section,
|
|
/// and the same for structs.
|
|
///
|
|
/// Note that this routine is very strict and tries to find a partition of the
|
|
/// type which produces the *exact* right offset and size. It is not forgiving
|
|
/// when the size or offset cause either end of type-based partition to be off.
|
|
/// Also, this is a best-effort routine. It is reasonable to give up and not
|
|
/// return a type if necessary.
|
|
static Type *getTypePartition(const TargetData &TD, Type *Ty,
|
|
uint64_t Offset, uint64_t Size) {
|
|
if (Offset == 0 && TD.getTypeAllocSize(Ty) == Size)
|
|
return Ty;
|
|
|
|
if (SequentialType *SeqTy = dyn_cast<SequentialType>(Ty)) {
|
|
// We can't partition pointers...
|
|
if (SeqTy->isPointerTy())
|
|
return 0;
|
|
|
|
Type *ElementTy = SeqTy->getElementType();
|
|
uint64_t ElementSize = TD.getTypeAllocSize(ElementTy);
|
|
uint64_t NumSkippedElements = Offset / ElementSize;
|
|
if (ArrayType *ArrTy = dyn_cast<ArrayType>(SeqTy))
|
|
if (NumSkippedElements >= ArrTy->getNumElements())
|
|
return 0;
|
|
if (VectorType *VecTy = dyn_cast<VectorType>(SeqTy))
|
|
if (NumSkippedElements >= VecTy->getNumElements())
|
|
return 0;
|
|
Offset -= NumSkippedElements * ElementSize;
|
|
|
|
// First check if we need to recurse.
|
|
if (Offset > 0 || Size < ElementSize) {
|
|
// Bail if the partition ends in a different array element.
|
|
if ((Offset + Size) > ElementSize)
|
|
return 0;
|
|
// Recurse through the element type trying to peel off offset bytes.
|
|
return getTypePartition(TD, ElementTy, Offset, Size);
|
|
}
|
|
assert(Offset == 0);
|
|
|
|
if (Size == ElementSize)
|
|
return ElementTy;
|
|
assert(Size > ElementSize);
|
|
uint64_t NumElements = Size / ElementSize;
|
|
if (NumElements * ElementSize != Size)
|
|
return 0;
|
|
return ArrayType::get(ElementTy, NumElements);
|
|
}
|
|
|
|
StructType *STy = dyn_cast<StructType>(Ty);
|
|
if (!STy)
|
|
return 0;
|
|
|
|
const StructLayout *SL = TD.getStructLayout(STy);
|
|
if (Offset >= SL->getSizeInBytes())
|
|
return 0;
|
|
uint64_t EndOffset = Offset + Size;
|
|
if (EndOffset > SL->getSizeInBytes())
|
|
return 0;
|
|
|
|
unsigned Index = SL->getElementContainingOffset(Offset);
|
|
Offset -= SL->getElementOffset(Index);
|
|
|
|
Type *ElementTy = STy->getElementType(Index);
|
|
uint64_t ElementSize = TD.getTypeAllocSize(ElementTy);
|
|
if (Offset >= ElementSize)
|
|
return 0; // The offset points into alignment padding.
|
|
|
|
// See if any partition must be contained by the element.
|
|
if (Offset > 0 || Size < ElementSize) {
|
|
if ((Offset + Size) > ElementSize)
|
|
return 0;
|
|
return getTypePartition(TD, ElementTy, Offset, Size);
|
|
}
|
|
assert(Offset == 0);
|
|
|
|
if (Size == ElementSize)
|
|
return ElementTy;
|
|
|
|
StructType::element_iterator EI = STy->element_begin() + Index,
|
|
EE = STy->element_end();
|
|
if (EndOffset < SL->getSizeInBytes()) {
|
|
unsigned EndIndex = SL->getElementContainingOffset(EndOffset);
|
|
if (Index == EndIndex)
|
|
return 0; // Within a single element and its padding.
|
|
|
|
// Don't try to form "natural" types if the elements don't line up with the
|
|
// expected size.
|
|
// FIXME: We could potentially recurse down through the last element in the
|
|
// sub-struct to find a natural end point.
|
|
if (SL->getElementOffset(EndIndex) != EndOffset)
|
|
return 0;
|
|
|
|
assert(Index < EndIndex);
|
|
EE = STy->element_begin() + EndIndex;
|
|
}
|
|
|
|
// Try to build up a sub-structure.
|
|
SmallVector<Type *, 4> ElementTys;
|
|
do {
|
|
ElementTys.push_back(*EI++);
|
|
} while (EI != EE);
|
|
StructType *SubTy = StructType::get(STy->getContext(), ElementTys,
|
|
STy->isPacked());
|
|
const StructLayout *SubSL = TD.getStructLayout(SubTy);
|
|
if (Size != SubSL->getSizeInBytes())
|
|
return 0; // The sub-struct doesn't have quite the size needed.
|
|
|
|
return SubTy;
|
|
}
|
|
|
|
/// \brief Rewrite an alloca partition's users.
|
|
///
|
|
/// This routine drives both of the rewriting goals of the SROA pass. It tries
|
|
/// to rewrite uses of an alloca partition to be conducive for SSA value
|
|
/// promotion. If the partition needs a new, more refined alloca, this will
|
|
/// build that new alloca, preserving as much type information as possible, and
|
|
/// rewrite the uses of the old alloca to point at the new one and have the
|
|
/// appropriate new offsets. It also evaluates how successful the rewrite was
|
|
/// at enabling promotion and if it was successful queues the alloca to be
|
|
/// promoted.
|
|
bool SROA::rewriteAllocaPartition(AllocaInst &AI,
|
|
AllocaPartitioning &P,
|
|
AllocaPartitioning::iterator PI) {
|
|
uint64_t AllocaSize = PI->EndOffset - PI->BeginOffset;
|
|
if (P.use_begin(PI) == P.use_end(PI))
|
|
return false; // No live uses left of this partition.
|
|
|
|
// Try to compute a friendly type for this partition of the alloca. This
|
|
// won't always succeed, in which case we fall back to a legal integer type
|
|
// or an i8 array of an appropriate size.
|
|
Type *AllocaTy = 0;
|
|
if (Type *PartitionTy = P.getCommonType(PI))
|
|
if (TD->getTypeAllocSize(PartitionTy) >= AllocaSize)
|
|
AllocaTy = PartitionTy;
|
|
if (!AllocaTy)
|
|
if (Type *PartitionTy = getTypePartition(*TD, AI.getAllocatedType(),
|
|
PI->BeginOffset, AllocaSize))
|
|
AllocaTy = PartitionTy;
|
|
if ((!AllocaTy ||
|
|
(AllocaTy->isArrayTy() &&
|
|
AllocaTy->getArrayElementType()->isIntegerTy())) &&
|
|
TD->isLegalInteger(AllocaSize * 8))
|
|
AllocaTy = Type::getIntNTy(*C, AllocaSize * 8);
|
|
if (!AllocaTy)
|
|
AllocaTy = ArrayType::get(Type::getInt8Ty(*C), AllocaSize);
|
|
assert(TD->getTypeAllocSize(AllocaTy) >= AllocaSize);
|
|
|
|
// Check for the case where we're going to rewrite to a new alloca of the
|
|
// exact same type as the original, and with the same access offsets. In that
|
|
// case, re-use the existing alloca, but still run through the rewriter to
|
|
// performe phi and select speculation.
|
|
AllocaInst *NewAI;
|
|
if (AllocaTy == AI.getAllocatedType()) {
|
|
assert(PI->BeginOffset == 0 &&
|
|
"Non-zero begin offset but same alloca type");
|
|
assert(PI == P.begin() && "Begin offset is zero on later partition");
|
|
NewAI = &AI;
|
|
} else {
|
|
// FIXME: The alignment here is overly conservative -- we could in many
|
|
// cases get away with much weaker alignment constraints.
|
|
NewAI = new AllocaInst(AllocaTy, 0, AI.getAlignment(),
|
|
AI.getName() + ".sroa." + Twine(PI - P.begin()),
|
|
&AI);
|
|
++NumNewAllocas;
|
|
}
|
|
|
|
DEBUG(dbgs() << "Rewriting alloca partition "
|
|
<< "[" << PI->BeginOffset << "," << PI->EndOffset << ") to: "
|
|
<< *NewAI << "\n");
|
|
|
|
AllocaPartitionRewriter Rewriter(*TD, P, PI, *this, AI, *NewAI,
|
|
PI->BeginOffset, PI->EndOffset);
|
|
DEBUG(dbgs() << " rewriting ");
|
|
DEBUG(P.print(dbgs(), PI, ""));
|
|
if (Rewriter.visitUsers(P.use_begin(PI), P.use_end(PI))) {
|
|
DEBUG(dbgs() << " and queuing for promotion\n");
|
|
PromotableAllocas.push_back(NewAI);
|
|
} else if (NewAI != &AI) {
|
|
// If we can't promote the alloca, iterate on it to check for new
|
|
// refinements exposed by splitting the current alloca. Don't iterate on an
|
|
// alloca which didn't actually change and didn't get promoted.
|
|
Worklist.insert(NewAI);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// \brief Walks the partitioning of an alloca rewriting uses of each partition.
|
|
bool SROA::splitAlloca(AllocaInst &AI, AllocaPartitioning &P) {
|
|
bool Changed = false;
|
|
for (AllocaPartitioning::iterator PI = P.begin(), PE = P.end(); PI != PE;
|
|
++PI)
|
|
Changed |= rewriteAllocaPartition(AI, P, PI);
|
|
|
|
return Changed;
|
|
}
|
|
|
|
/// \brief Analyze an alloca for SROA.
|
|
///
|
|
/// This analyzes the alloca to ensure we can reason about it, builds
|
|
/// a partitioning of the alloca, and then hands it off to be split and
|
|
/// rewritten as needed.
|
|
bool SROA::runOnAlloca(AllocaInst &AI) {
|
|
DEBUG(dbgs() << "SROA alloca: " << AI << "\n");
|
|
++NumAllocasAnalyzed;
|
|
|
|
// Special case dead allocas, as they're trivial.
|
|
if (AI.use_empty()) {
|
|
AI.eraseFromParent();
|
|
return true;
|
|
}
|
|
|
|
// Skip alloca forms that this analysis can't handle.
|
|
if (AI.isArrayAllocation() || !AI.getAllocatedType()->isSized() ||
|
|
TD->getTypeAllocSize(AI.getAllocatedType()) == 0)
|
|
return false;
|
|
|
|
// First check if this is a non-aggregate type that we should simply promote.
|
|
if (!AI.getAllocatedType()->isAggregateType() && isAllocaPromotable(&AI)) {
|
|
DEBUG(dbgs() << " Trivially scalar type, queuing for promotion...\n");
|
|
PromotableAllocas.push_back(&AI);
|
|
return false;
|
|
}
|
|
|
|
// Build the partition set using a recursive instruction-visiting builder.
|
|
AllocaPartitioning P(*TD, AI);
|
|
DEBUG(P.print(dbgs()));
|
|
if (P.isEscaped())
|
|
return false;
|
|
|
|
// No partitions to split. Leave the dead alloca for a later pass to clean up.
|
|
if (P.begin() == P.end())
|
|
return false;
|
|
|
|
// Delete all the dead users of this alloca before splitting and rewriting it.
|
|
bool Changed = false;
|
|
for (AllocaPartitioning::dead_user_iterator DI = P.dead_user_begin(),
|
|
DE = P.dead_user_end();
|
|
DI != DE; ++DI) {
|
|
Changed = true;
|
|
(*DI)->replaceAllUsesWith(UndefValue::get((*DI)->getType()));
|
|
DeadInsts.push_back(*DI);
|
|
}
|
|
for (AllocaPartitioning::dead_op_iterator DO = P.dead_op_begin(),
|
|
DE = P.dead_op_end();
|
|
DO != DE; ++DO) {
|
|
Value *OldV = **DO;
|
|
// Clobber the use with an undef value.
|
|
**DO = UndefValue::get(OldV->getType());
|
|
if (Instruction *OldI = dyn_cast<Instruction>(OldV))
|
|
if (isInstructionTriviallyDead(OldI)) {
|
|
Changed = true;
|
|
DeadInsts.push_back(OldI);
|
|
}
|
|
}
|
|
|
|
return splitAlloca(AI, P) || Changed;
|
|
}
|
|
|
|
/// \brief Delete the dead instructions accumulated in this run.
|
|
///
|
|
/// Recursively deletes the dead instructions we've accumulated. This is done
|
|
/// at the very end to maximize locality of the recursive delete and to
|
|
/// minimize the problems of invalidated instruction pointers as such pointers
|
|
/// are used heavily in the intermediate stages of the algorithm.
|
|
///
|
|
/// We also record the alloca instructions deleted here so that they aren't
|
|
/// subsequently handed to mem2reg to promote.
|
|
void SROA::deleteDeadInstructions(SmallPtrSet<AllocaInst*, 4> &DeletedAllocas) {
|
|
DeadSplitInsts.clear();
|
|
while (!DeadInsts.empty()) {
|
|
Instruction *I = DeadInsts.pop_back_val();
|
|
DEBUG(dbgs() << "Deleting dead instruction: " << *I << "\n");
|
|
|
|
for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
|
|
if (Instruction *U = dyn_cast<Instruction>(*OI)) {
|
|
// Zero out the operand and see if it becomes trivially dead.
|
|
*OI = 0;
|
|
if (isInstructionTriviallyDead(U))
|
|
DeadInsts.push_back(U);
|
|
}
|
|
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
|
|
DeletedAllocas.insert(AI);
|
|
|
|
++NumDeleted;
|
|
I->eraseFromParent();
|
|
}
|
|
}
|
|
|
|
/// \brief Promote the allocas, using the best available technique.
|
|
///
|
|
/// This attempts to promote whatever allocas have been identified as viable in
|
|
/// the PromotableAllocas list. If that list is empty, there is nothing to do.
|
|
/// If there is a domtree available, we attempt to promote using the full power
|
|
/// of mem2reg. Otherwise, we build and use the AllocaPromoter above which is
|
|
/// based on the SSAUpdater utilities. This function returns whether any
|
|
/// promotion occured.
|
|
bool SROA::promoteAllocas(Function &F) {
|
|
if (PromotableAllocas.empty())
|
|
return false;
|
|
|
|
NumPromoted += PromotableAllocas.size();
|
|
|
|
if (DT && !ForceSSAUpdater) {
|
|
DEBUG(dbgs() << "Promoting allocas with mem2reg...\n");
|
|
PromoteMemToReg(PromotableAllocas, *DT);
|
|
PromotableAllocas.clear();
|
|
return true;
|
|
}
|
|
|
|
DEBUG(dbgs() << "Promoting allocas with SSAUpdater...\n");
|
|
SSAUpdater SSA;
|
|
DIBuilder DIB(*F.getParent());
|
|
SmallVector<Instruction*, 64> Insts;
|
|
|
|
for (unsigned Idx = 0, Size = PromotableAllocas.size(); Idx != Size; ++Idx) {
|
|
AllocaInst *AI = PromotableAllocas[Idx];
|
|
for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
|
|
UI != UE;) {
|
|
Instruction *I = cast<Instruction>(*UI++);
|
|
// FIXME: Currently the SSAUpdater infrastructure doesn't reason about
|
|
// lifetime intrinsics and so we strip them (and the bitcasts+GEPs
|
|
// leading to them) here. Eventually it should use them to optimize the
|
|
// scalar values produced.
|
|
if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
|
|
assert(onlyUsedByLifetimeMarkers(I) &&
|
|
"Found a bitcast used outside of a lifetime marker.");
|
|
while (!I->use_empty())
|
|
cast<Instruction>(*I->use_begin())->eraseFromParent();
|
|
I->eraseFromParent();
|
|
continue;
|
|
}
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
|
|
assert(II->getIntrinsicID() == Intrinsic::lifetime_start ||
|
|
II->getIntrinsicID() == Intrinsic::lifetime_end);
|
|
II->eraseFromParent();
|
|
continue;
|
|
}
|
|
|
|
Insts.push_back(I);
|
|
}
|
|
AllocaPromoter(Insts, SSA, *AI, DIB).run(Insts);
|
|
Insts.clear();
|
|
}
|
|
|
|
PromotableAllocas.clear();
|
|
return true;
|
|
}
|
|
|
|
namespace {
|
|
/// \brief A predicate to test whether an alloca belongs to a set.
|
|
class IsAllocaInSet {
|
|
typedef SmallPtrSet<AllocaInst *, 4> SetType;
|
|
const SetType &Set;
|
|
|
|
public:
|
|
IsAllocaInSet(const SetType &Set) : Set(Set) {}
|
|
bool operator()(AllocaInst *AI) { return Set.count(AI); }
|
|
};
|
|
}
|
|
|
|
bool SROA::runOnFunction(Function &F) {
|
|
DEBUG(dbgs() << "SROA function: " << F.getName() << "\n");
|
|
C = &F.getContext();
|
|
TD = getAnalysisIfAvailable<TargetData>();
|
|
if (!TD) {
|
|
DEBUG(dbgs() << " Skipping SROA -- no target data!\n");
|
|
return false;
|
|
}
|
|
DT = getAnalysisIfAvailable<DominatorTree>();
|
|
|
|
BasicBlock &EntryBB = F.getEntryBlock();
|
|
for (BasicBlock::iterator I = EntryBB.begin(), E = llvm::prior(EntryBB.end());
|
|
I != E; ++I)
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
|
|
Worklist.insert(AI);
|
|
|
|
bool Changed = false;
|
|
// A set of deleted alloca instruction pointers which should be removed from
|
|
// the list of promotable allocas.
|
|
SmallPtrSet<AllocaInst *, 4> DeletedAllocas;
|
|
|
|
while (!Worklist.empty()) {
|
|
Changed |= runOnAlloca(*Worklist.pop_back_val());
|
|
deleteDeadInstructions(DeletedAllocas);
|
|
if (!DeletedAllocas.empty()) {
|
|
PromotableAllocas.erase(std::remove_if(PromotableAllocas.begin(),
|
|
PromotableAllocas.end(),
|
|
IsAllocaInSet(DeletedAllocas)),
|
|
PromotableAllocas.end());
|
|
DeletedAllocas.clear();
|
|
}
|
|
}
|
|
|
|
Changed |= promoteAllocas(F);
|
|
|
|
return Changed;
|
|
}
|
|
|
|
void SROA::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
if (RequiresDomTree)
|
|
AU.addRequired<DominatorTree>();
|
|
AU.setPreservesCFG();
|
|
}
|