mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237375 91177308-0d34-0410-b5e6-96231b3b80d8
785 lines
28 KiB
C++
785 lines
28 KiB
C++
//===-- StackColoring.cpp -------------------------------------------------===//
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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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//
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// This pass implements the stack-coloring optimization that looks for
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// lifetime markers machine instructions (LIFESTART_BEGIN and LIFESTART_END),
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// which represent the possible lifetime of stack slots. It attempts to
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// merge disjoint stack slots and reduce the used stack space.
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// NOTE: This pass is not StackSlotColoring, which optimizes spill slots.
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//
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// TODO: In the future we plan to improve stack coloring in the following ways:
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// 1. Allow merging multiple small slots into a single larger slot at different
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// offsets.
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// 2. Merge this pass with StackSlotColoring and allow merging of allocas with
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// spill slots.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/ADT/BitVector.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SparseSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/CodeGen/LiveInterval.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
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#include "llvm/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/CodeGen/MachineMemOperand.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/PseudoSourceValue.h"
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#include "llvm/CodeGen/SlotIndexes.h"
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#include "llvm/CodeGen/StackProtector.h"
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#include "llvm/IR/DebugInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Module.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/raw_ostream.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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using namespace llvm;
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#define DEBUG_TYPE "stackcoloring"
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static cl::opt<bool>
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DisableColoring("no-stack-coloring",
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cl::init(false), cl::Hidden,
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cl::desc("Disable stack coloring"));
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/// The user may write code that uses allocas outside of the declared lifetime
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/// zone. This can happen when the user returns a reference to a local
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/// data-structure. We can detect these cases and decide not to optimize the
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/// code. If this flag is enabled, we try to save the user.
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static cl::opt<bool>
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ProtectFromEscapedAllocas("protect-from-escaped-allocas",
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cl::init(false), cl::Hidden,
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cl::desc("Do not optimize lifetime zones that "
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"are broken"));
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STATISTIC(NumMarkerSeen, "Number of lifetime markers found.");
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STATISTIC(StackSpaceSaved, "Number of bytes saved due to merging slots.");
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STATISTIC(StackSlotMerged, "Number of stack slot merged.");
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STATISTIC(EscapedAllocas, "Number of allocas that escaped the lifetime region");
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//===----------------------------------------------------------------------===//
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// StackColoring Pass
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//===----------------------------------------------------------------------===//
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namespace {
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/// StackColoring - A machine pass for merging disjoint stack allocations,
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/// marked by the LIFETIME_START and LIFETIME_END pseudo instructions.
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class StackColoring : public MachineFunctionPass {
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MachineFrameInfo *MFI;
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MachineFunction *MF;
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/// A class representing liveness information for a single basic block.
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/// Each bit in the BitVector represents the liveness property
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/// for a different stack slot.
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struct BlockLifetimeInfo {
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/// Which slots BEGINs in each basic block.
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BitVector Begin;
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/// Which slots ENDs in each basic block.
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BitVector End;
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/// Which slots are marked as LIVE_IN, coming into each basic block.
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BitVector LiveIn;
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/// Which slots are marked as LIVE_OUT, coming out of each basic block.
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BitVector LiveOut;
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};
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/// Maps active slots (per bit) for each basic block.
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typedef DenseMap<const MachineBasicBlock*, BlockLifetimeInfo> LivenessMap;
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LivenessMap BlockLiveness;
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/// Maps serial numbers to basic blocks.
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DenseMap<const MachineBasicBlock*, int> BasicBlocks;
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/// Maps basic blocks to a serial number.
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SmallVector<const MachineBasicBlock*, 8> BasicBlockNumbering;
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/// Maps liveness intervals for each slot.
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SmallVector<std::unique_ptr<LiveInterval>, 16> Intervals;
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/// VNInfo is used for the construction of LiveIntervals.
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VNInfo::Allocator VNInfoAllocator;
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/// SlotIndex analysis object.
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SlotIndexes *Indexes;
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/// The stack protector object.
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StackProtector *SP;
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/// The list of lifetime markers found. These markers are to be removed
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/// once the coloring is done.
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SmallVector<MachineInstr*, 8> Markers;
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public:
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static char ID;
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StackColoring() : MachineFunctionPass(ID) {
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initializeStackColoringPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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bool runOnMachineFunction(MachineFunction &MF) override;
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private:
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/// Debug.
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void dump() const;
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/// Removes all of the lifetime marker instructions from the function.
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/// \returns true if any markers were removed.
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bool removeAllMarkers();
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/// Scan the machine function and find all of the lifetime markers.
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/// Record the findings in the BEGIN and END vectors.
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/// \returns the number of markers found.
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unsigned collectMarkers(unsigned NumSlot);
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/// Perform the dataflow calculation and calculate the lifetime for each of
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/// the slots, based on the BEGIN/END vectors. Set the LifetimeLIVE_IN and
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/// LifetimeLIVE_OUT maps that represent which stack slots are live coming
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/// in and out blocks.
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void calculateLocalLiveness();
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/// Construct the LiveIntervals for the slots.
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void calculateLiveIntervals(unsigned NumSlots);
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/// Go over the machine function and change instructions which use stack
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/// slots to use the joint slots.
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void remapInstructions(DenseMap<int, int> &SlotRemap);
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/// The input program may contain instructions which are not inside lifetime
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/// markers. This can happen due to a bug in the compiler or due to a bug in
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/// user code (for example, returning a reference to a local variable).
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/// This procedure checks all of the instructions in the function and
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/// invalidates lifetime ranges which do not contain all of the instructions
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/// which access that frame slot.
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void removeInvalidSlotRanges();
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/// Map entries which point to other entries to their destination.
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/// A->B->C becomes A->C.
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void expungeSlotMap(DenseMap<int, int> &SlotRemap, unsigned NumSlots);
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};
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} // end anonymous namespace
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char StackColoring::ID = 0;
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char &llvm::StackColoringID = StackColoring::ID;
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INITIALIZE_PASS_BEGIN(StackColoring,
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"stack-coloring", "Merge disjoint stack slots", false, false)
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INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
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INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
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INITIALIZE_PASS_DEPENDENCY(StackProtector)
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INITIALIZE_PASS_END(StackColoring,
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"stack-coloring", "Merge disjoint stack slots", false, false)
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void StackColoring::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<MachineDominatorTree>();
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AU.addPreserved<MachineDominatorTree>();
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AU.addRequired<SlotIndexes>();
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AU.addRequired<StackProtector>();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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void StackColoring::dump() const {
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for (MachineBasicBlock *MBB : depth_first(MF)) {
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DEBUG(dbgs() << "Inspecting block #" << BasicBlocks.lookup(MBB) << " ["
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<< MBB->getName() << "]\n");
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LivenessMap::const_iterator BI = BlockLiveness.find(MBB);
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assert(BI != BlockLiveness.end() && "Block not found");
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const BlockLifetimeInfo &BlockInfo = BI->second;
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DEBUG(dbgs()<<"BEGIN : {");
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for (unsigned i=0; i < BlockInfo.Begin.size(); ++i)
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DEBUG(dbgs()<<BlockInfo.Begin.test(i)<<" ");
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DEBUG(dbgs()<<"}\n");
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DEBUG(dbgs()<<"END : {");
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for (unsigned i=0; i < BlockInfo.End.size(); ++i)
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DEBUG(dbgs()<<BlockInfo.End.test(i)<<" ");
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DEBUG(dbgs()<<"}\n");
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DEBUG(dbgs()<<"LIVE_IN: {");
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for (unsigned i=0; i < BlockInfo.LiveIn.size(); ++i)
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DEBUG(dbgs()<<BlockInfo.LiveIn.test(i)<<" ");
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DEBUG(dbgs()<<"}\n");
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DEBUG(dbgs()<<"LIVEOUT: {");
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for (unsigned i=0; i < BlockInfo.LiveOut.size(); ++i)
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DEBUG(dbgs()<<BlockInfo.LiveOut.test(i)<<" ");
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DEBUG(dbgs()<<"}\n");
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}
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}
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unsigned StackColoring::collectMarkers(unsigned NumSlot) {
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unsigned MarkersFound = 0;
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// Scan the function to find all lifetime markers.
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// NOTE: We use a reverse-post-order iteration to ensure that we obtain a
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// deterministic numbering, and because we'll need a post-order iteration
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// later for solving the liveness dataflow problem.
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for (MachineBasicBlock *MBB : depth_first(MF)) {
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// Assign a serial number to this basic block.
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BasicBlocks[MBB] = BasicBlockNumbering.size();
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BasicBlockNumbering.push_back(MBB);
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// Keep a reference to avoid repeated lookups.
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BlockLifetimeInfo &BlockInfo = BlockLiveness[MBB];
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BlockInfo.Begin.resize(NumSlot);
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BlockInfo.End.resize(NumSlot);
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for (MachineInstr &MI : *MBB) {
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if (MI.getOpcode() != TargetOpcode::LIFETIME_START &&
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MI.getOpcode() != TargetOpcode::LIFETIME_END)
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continue;
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Markers.push_back(&MI);
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bool IsStart = MI.getOpcode() == TargetOpcode::LIFETIME_START;
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const MachineOperand &MO = MI.getOperand(0);
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unsigned Slot = MO.getIndex();
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MarkersFound++;
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const AllocaInst *Allocation = MFI->getObjectAllocation(Slot);
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if (Allocation) {
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DEBUG(dbgs()<<"Found a lifetime marker for slot #"<<Slot<<
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" with allocation: "<< Allocation->getName()<<"\n");
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}
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if (IsStart) {
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BlockInfo.Begin.set(Slot);
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} else {
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if (BlockInfo.Begin.test(Slot)) {
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// Allocas that start and end within a single block are handled
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// specially when computing the LiveIntervals to avoid pessimizing
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// the liveness propagation.
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BlockInfo.Begin.reset(Slot);
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} else {
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BlockInfo.End.set(Slot);
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}
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}
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}
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}
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// Update statistics.
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NumMarkerSeen += MarkersFound;
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return MarkersFound;
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}
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void StackColoring::calculateLocalLiveness() {
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// Perform a standard reverse dataflow computation to solve for
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// global liveness. The BEGIN set here is equivalent to KILL in the standard
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// formulation, and END is equivalent to GEN. The result of this computation
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// is a map from blocks to bitvectors where the bitvectors represent which
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// allocas are live in/out of that block.
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SmallPtrSet<const MachineBasicBlock*, 8> BBSet(BasicBlockNumbering.begin(),
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BasicBlockNumbering.end());
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unsigned NumSSMIters = 0;
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bool changed = true;
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while (changed) {
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changed = false;
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++NumSSMIters;
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SmallPtrSet<const MachineBasicBlock*, 8> NextBBSet;
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for (const MachineBasicBlock *BB : BasicBlockNumbering) {
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if (!BBSet.count(BB)) continue;
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// Use an iterator to avoid repeated lookups.
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LivenessMap::iterator BI = BlockLiveness.find(BB);
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assert(BI != BlockLiveness.end() && "Block not found");
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BlockLifetimeInfo &BlockInfo = BI->second;
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BitVector LocalLiveIn;
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BitVector LocalLiveOut;
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// Forward propagation from begins to ends.
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for (MachineBasicBlock::const_pred_iterator PI = BB->pred_begin(),
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PE = BB->pred_end(); PI != PE; ++PI) {
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LivenessMap::const_iterator I = BlockLiveness.find(*PI);
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assert(I != BlockLiveness.end() && "Predecessor not found");
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LocalLiveIn |= I->second.LiveOut;
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}
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LocalLiveIn |= BlockInfo.End;
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LocalLiveIn.reset(BlockInfo.Begin);
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// Reverse propagation from ends to begins.
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for (MachineBasicBlock::const_succ_iterator SI = BB->succ_begin(),
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SE = BB->succ_end(); SI != SE; ++SI) {
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LivenessMap::const_iterator I = BlockLiveness.find(*SI);
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assert(I != BlockLiveness.end() && "Successor not found");
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LocalLiveOut |= I->second.LiveIn;
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}
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LocalLiveOut |= BlockInfo.Begin;
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LocalLiveOut.reset(BlockInfo.End);
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LocalLiveIn |= LocalLiveOut;
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LocalLiveOut |= LocalLiveIn;
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// After adopting the live bits, we need to turn-off the bits which
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// are de-activated in this block.
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LocalLiveOut.reset(BlockInfo.End);
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LocalLiveIn.reset(BlockInfo.Begin);
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// If we have both BEGIN and END markers in the same basic block then
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// we know that the BEGIN marker comes after the END, because we already
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// handle the case where the BEGIN comes before the END when collecting
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// the markers (and building the BEGIN/END vectore).
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// Want to enable the LIVE_IN and LIVE_OUT of slots that have both
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// BEGIN and END because it means that the value lives before and after
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// this basic block.
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BitVector LocalEndBegin = BlockInfo.End;
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LocalEndBegin &= BlockInfo.Begin;
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LocalLiveIn |= LocalEndBegin;
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LocalLiveOut |= LocalEndBegin;
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if (LocalLiveIn.test(BlockInfo.LiveIn)) {
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changed = true;
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BlockInfo.LiveIn |= LocalLiveIn;
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NextBBSet.insert(BB->pred_begin(), BB->pred_end());
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}
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if (LocalLiveOut.test(BlockInfo.LiveOut)) {
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changed = true;
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BlockInfo.LiveOut |= LocalLiveOut;
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NextBBSet.insert(BB->succ_begin(), BB->succ_end());
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}
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}
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BBSet = std::move(NextBBSet);
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}// while changed.
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}
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void StackColoring::calculateLiveIntervals(unsigned NumSlots) {
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SmallVector<SlotIndex, 16> Starts;
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SmallVector<SlotIndex, 16> Finishes;
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// For each block, find which slots are active within this block
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// and update the live intervals.
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for (const MachineBasicBlock &MBB : *MF) {
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Starts.clear();
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Starts.resize(NumSlots);
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Finishes.clear();
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Finishes.resize(NumSlots);
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// Create the interval for the basic blocks with lifetime markers in them.
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for (const MachineInstr *MI : Markers) {
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if (MI->getParent() != &MBB)
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continue;
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assert((MI->getOpcode() == TargetOpcode::LIFETIME_START ||
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MI->getOpcode() == TargetOpcode::LIFETIME_END) &&
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"Invalid Lifetime marker");
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bool IsStart = MI->getOpcode() == TargetOpcode::LIFETIME_START;
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const MachineOperand &Mo = MI->getOperand(0);
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int Slot = Mo.getIndex();
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assert(Slot >= 0 && "Invalid slot");
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SlotIndex ThisIndex = Indexes->getInstructionIndex(MI);
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if (IsStart) {
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if (!Starts[Slot].isValid() || Starts[Slot] > ThisIndex)
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Starts[Slot] = ThisIndex;
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} else {
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if (!Finishes[Slot].isValid() || Finishes[Slot] < ThisIndex)
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Finishes[Slot] = ThisIndex;
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}
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}
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// Create the interval of the blocks that we previously found to be 'alive'.
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BlockLifetimeInfo &MBBLiveness = BlockLiveness[&MBB];
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for (int pos = MBBLiveness.LiveIn.find_first(); pos != -1;
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pos = MBBLiveness.LiveIn.find_next(pos)) {
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Starts[pos] = Indexes->getMBBStartIdx(&MBB);
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}
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for (int pos = MBBLiveness.LiveOut.find_first(); pos != -1;
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pos = MBBLiveness.LiveOut.find_next(pos)) {
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Finishes[pos] = Indexes->getMBBEndIdx(&MBB);
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}
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for (unsigned i = 0; i < NumSlots; ++i) {
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assert(Starts[i].isValid() == Finishes[i].isValid() && "Unmatched range");
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if (!Starts[i].isValid())
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continue;
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assert(Starts[i] && Finishes[i] && "Invalid interval");
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VNInfo *ValNum = Intervals[i]->getValNumInfo(0);
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SlotIndex S = Starts[i];
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SlotIndex F = Finishes[i];
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if (S < F) {
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// We have a single consecutive region.
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Intervals[i]->addSegment(LiveInterval::Segment(S, F, ValNum));
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} else {
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// We have two non-consecutive regions. This happens when
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// LIFETIME_START appears after the LIFETIME_END marker.
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SlotIndex NewStart = Indexes->getMBBStartIdx(&MBB);
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SlotIndex NewFin = Indexes->getMBBEndIdx(&MBB);
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Intervals[i]->addSegment(LiveInterval::Segment(NewStart, F, ValNum));
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Intervals[i]->addSegment(LiveInterval::Segment(S, NewFin, ValNum));
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}
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}
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}
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}
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bool StackColoring::removeAllMarkers() {
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unsigned Count = 0;
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for (MachineInstr *MI : Markers) {
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MI->eraseFromParent();
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Count++;
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}
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Markers.clear();
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DEBUG(dbgs()<<"Removed "<<Count<<" markers.\n");
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return Count;
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}
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void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
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unsigned FixedInstr = 0;
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unsigned FixedMemOp = 0;
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unsigned FixedDbg = 0;
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MachineModuleInfo *MMI = &MF->getMMI();
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// Remap debug information that refers to stack slots.
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for (auto &VI : MMI->getVariableDbgInfo()) {
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if (!VI.Var)
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continue;
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if (SlotRemap.count(VI.Slot)) {
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DEBUG(dbgs() << "Remapping debug info for ["
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<< cast<DILocalVariable>(VI.Var)->getName() << "].\n");
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VI.Slot = SlotRemap[VI.Slot];
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FixedDbg++;
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}
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}
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// Keep a list of *allocas* which need to be remapped.
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DenseMap<const AllocaInst*, const AllocaInst*> Allocas;
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for (const std::pair<int, int> &SI : SlotRemap) {
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const AllocaInst *From = MFI->getObjectAllocation(SI.first);
|
|
const AllocaInst *To = MFI->getObjectAllocation(SI.second);
|
|
assert(To && From && "Invalid allocation object");
|
|
Allocas[From] = To;
|
|
|
|
// AA might be used later for instruction scheduling, and we need it to be
|
|
// able to deduce the correct aliasing releationships between pointers
|
|
// derived from the alloca being remapped and the target of that remapping.
|
|
// The only safe way, without directly informing AA about the remapping
|
|
// somehow, is to directly update the IR to reflect the change being made
|
|
// here.
|
|
Instruction *Inst = const_cast<AllocaInst *>(To);
|
|
if (From->getType() != To->getType()) {
|
|
BitCastInst *Cast = new BitCastInst(Inst, From->getType());
|
|
Cast->insertAfter(Inst);
|
|
Inst = Cast;
|
|
}
|
|
|
|
// Allow the stack protector to adjust its value map to account for the
|
|
// upcoming replacement.
|
|
SP->adjustForColoring(From, To);
|
|
|
|
// Note that this will not replace uses in MMOs (which we'll update below),
|
|
// or anywhere else (which is why we won't delete the original
|
|
// instruction).
|
|
const_cast<AllocaInst *>(From)->replaceAllUsesWith(Inst);
|
|
}
|
|
|
|
// Remap all instructions to the new stack slots.
|
|
for (MachineBasicBlock &BB : *MF)
|
|
for (MachineInstr &I : BB) {
|
|
// Skip lifetime markers. We'll remove them soon.
|
|
if (I.getOpcode() == TargetOpcode::LIFETIME_START ||
|
|
I.getOpcode() == TargetOpcode::LIFETIME_END)
|
|
continue;
|
|
|
|
// Update the MachineMemOperand to use the new alloca.
|
|
for (MachineMemOperand *MMO : I.memoperands()) {
|
|
// FIXME: In order to enable the use of TBAA when using AA in CodeGen,
|
|
// we'll also need to update the TBAA nodes in MMOs with values
|
|
// derived from the merged allocas. When doing this, we'll need to use
|
|
// the same variant of GetUnderlyingObjects that is used by the
|
|
// instruction scheduler (that can look through ptrtoint/inttoptr
|
|
// pairs).
|
|
|
|
// We've replaced IR-level uses of the remapped allocas, so we only
|
|
// need to replace direct uses here.
|
|
const AllocaInst *AI = dyn_cast_or_null<AllocaInst>(MMO->getValue());
|
|
if (!AI)
|
|
continue;
|
|
|
|
if (!Allocas.count(AI))
|
|
continue;
|
|
|
|
MMO->setValue(Allocas[AI]);
|
|
FixedMemOp++;
|
|
}
|
|
|
|
// Update all of the machine instruction operands.
|
|
for (MachineOperand &MO : I.operands()) {
|
|
if (!MO.isFI())
|
|
continue;
|
|
int FromSlot = MO.getIndex();
|
|
|
|
// Don't touch arguments.
|
|
if (FromSlot<0)
|
|
continue;
|
|
|
|
// Only look at mapped slots.
|
|
if (!SlotRemap.count(FromSlot))
|
|
continue;
|
|
|
|
// In a debug build, check that the instruction that we are modifying is
|
|
// inside the expected live range. If the instruction is not inside
|
|
// the calculated range then it means that the alloca usage moved
|
|
// outside of the lifetime markers, or that the user has a bug.
|
|
// NOTE: Alloca address calculations which happen outside the lifetime
|
|
// zone are are okay, despite the fact that we don't have a good way
|
|
// for validating all of the usages of the calculation.
|
|
#ifndef NDEBUG
|
|
bool TouchesMemory = I.mayLoad() || I.mayStore();
|
|
// If we *don't* protect the user from escaped allocas, don't bother
|
|
// validating the instructions.
|
|
if (!I.isDebugValue() && TouchesMemory && ProtectFromEscapedAllocas) {
|
|
SlotIndex Index = Indexes->getInstructionIndex(&I);
|
|
const LiveInterval *Interval = &*Intervals[FromSlot];
|
|
assert(Interval->find(Index) != Interval->end() &&
|
|
"Found instruction usage outside of live range.");
|
|
}
|
|
#endif
|
|
|
|
// Fix the machine instructions.
|
|
int ToSlot = SlotRemap[FromSlot];
|
|
MO.setIndex(ToSlot);
|
|
FixedInstr++;
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs()<<"Fixed "<<FixedMemOp<<" machine memory operands.\n");
|
|
DEBUG(dbgs()<<"Fixed "<<FixedDbg<<" debug locations.\n");
|
|
DEBUG(dbgs()<<"Fixed "<<FixedInstr<<" machine instructions.\n");
|
|
}
|
|
|
|
void StackColoring::removeInvalidSlotRanges() {
|
|
for (MachineBasicBlock &BB : *MF)
|
|
for (MachineInstr &I : BB) {
|
|
if (I.getOpcode() == TargetOpcode::LIFETIME_START ||
|
|
I.getOpcode() == TargetOpcode::LIFETIME_END || I.isDebugValue())
|
|
continue;
|
|
|
|
// Some intervals are suspicious! In some cases we find address
|
|
// calculations outside of the lifetime zone, but not actual memory
|
|
// read or write. Memory accesses outside of the lifetime zone are a clear
|
|
// violation, but address calculations are okay. This can happen when
|
|
// GEPs are hoisted outside of the lifetime zone.
|
|
// So, in here we only check instructions which can read or write memory.
|
|
if (!I.mayLoad() && !I.mayStore())
|
|
continue;
|
|
|
|
// Check all of the machine operands.
|
|
for (const MachineOperand &MO : I.operands()) {
|
|
if (!MO.isFI())
|
|
continue;
|
|
|
|
int Slot = MO.getIndex();
|
|
|
|
if (Slot<0)
|
|
continue;
|
|
|
|
if (Intervals[Slot]->empty())
|
|
continue;
|
|
|
|
// Check that the used slot is inside the calculated lifetime range.
|
|
// If it is not, warn about it and invalidate the range.
|
|
LiveInterval *Interval = &*Intervals[Slot];
|
|
SlotIndex Index = Indexes->getInstructionIndex(&I);
|
|
if (Interval->find(Index) == Interval->end()) {
|
|
Interval->clear();
|
|
DEBUG(dbgs()<<"Invalidating range #"<<Slot<<"\n");
|
|
EscapedAllocas++;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void StackColoring::expungeSlotMap(DenseMap<int, int> &SlotRemap,
|
|
unsigned NumSlots) {
|
|
// Expunge slot remap map.
|
|
for (unsigned i=0; i < NumSlots; ++i) {
|
|
// If we are remapping i
|
|
if (SlotRemap.count(i)) {
|
|
int Target = SlotRemap[i];
|
|
// As long as our target is mapped to something else, follow it.
|
|
while (SlotRemap.count(Target)) {
|
|
Target = SlotRemap[Target];
|
|
SlotRemap[i] = Target;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
bool StackColoring::runOnMachineFunction(MachineFunction &Func) {
|
|
if (skipOptnoneFunction(*Func.getFunction()))
|
|
return false;
|
|
|
|
DEBUG(dbgs() << "********** Stack Coloring **********\n"
|
|
<< "********** Function: "
|
|
<< ((const Value*)Func.getFunction())->getName() << '\n');
|
|
MF = &Func;
|
|
MFI = MF->getFrameInfo();
|
|
Indexes = &getAnalysis<SlotIndexes>();
|
|
SP = &getAnalysis<StackProtector>();
|
|
BlockLiveness.clear();
|
|
BasicBlocks.clear();
|
|
BasicBlockNumbering.clear();
|
|
Markers.clear();
|
|
Intervals.clear();
|
|
VNInfoAllocator.Reset();
|
|
|
|
unsigned NumSlots = MFI->getObjectIndexEnd();
|
|
|
|
// If there are no stack slots then there are no markers to remove.
|
|
if (!NumSlots)
|
|
return false;
|
|
|
|
SmallVector<int, 8> SortedSlots;
|
|
|
|
SortedSlots.reserve(NumSlots);
|
|
Intervals.reserve(NumSlots);
|
|
|
|
unsigned NumMarkers = collectMarkers(NumSlots);
|
|
|
|
unsigned TotalSize = 0;
|
|
DEBUG(dbgs()<<"Found "<<NumMarkers<<" markers and "<<NumSlots<<" slots\n");
|
|
DEBUG(dbgs()<<"Slot structure:\n");
|
|
|
|
for (int i=0; i < MFI->getObjectIndexEnd(); ++i) {
|
|
DEBUG(dbgs()<<"Slot #"<<i<<" - "<<MFI->getObjectSize(i)<<" bytes.\n");
|
|
TotalSize += MFI->getObjectSize(i);
|
|
}
|
|
|
|
DEBUG(dbgs()<<"Total Stack size: "<<TotalSize<<" bytes\n\n");
|
|
|
|
// Don't continue because there are not enough lifetime markers, or the
|
|
// stack is too small, or we are told not to optimize the slots.
|
|
if (NumMarkers < 2 || TotalSize < 16 || DisableColoring) {
|
|
DEBUG(dbgs()<<"Will not try to merge slots.\n");
|
|
return removeAllMarkers();
|
|
}
|
|
|
|
for (unsigned i=0; i < NumSlots; ++i) {
|
|
std::unique_ptr<LiveInterval> LI(new LiveInterval(i, 0));
|
|
LI->getNextValue(Indexes->getZeroIndex(), VNInfoAllocator);
|
|
Intervals.push_back(std::move(LI));
|
|
SortedSlots.push_back(i);
|
|
}
|
|
|
|
// Calculate the liveness of each block.
|
|
calculateLocalLiveness();
|
|
|
|
// Propagate the liveness information.
|
|
calculateLiveIntervals(NumSlots);
|
|
|
|
// Search for allocas which are used outside of the declared lifetime
|
|
// markers.
|
|
if (ProtectFromEscapedAllocas)
|
|
removeInvalidSlotRanges();
|
|
|
|
// Maps old slots to new slots.
|
|
DenseMap<int, int> SlotRemap;
|
|
unsigned RemovedSlots = 0;
|
|
unsigned ReducedSize = 0;
|
|
|
|
// Do not bother looking at empty intervals.
|
|
for (unsigned I = 0; I < NumSlots; ++I) {
|
|
if (Intervals[SortedSlots[I]]->empty())
|
|
SortedSlots[I] = -1;
|
|
}
|
|
|
|
// This is a simple greedy algorithm for merging allocas. First, sort the
|
|
// slots, placing the largest slots first. Next, perform an n^2 scan and look
|
|
// for disjoint slots. When you find disjoint slots, merge the samller one
|
|
// into the bigger one and update the live interval. Remove the small alloca
|
|
// and continue.
|
|
|
|
// Sort the slots according to their size. Place unused slots at the end.
|
|
// Use stable sort to guarantee deterministic code generation.
|
|
std::stable_sort(SortedSlots.begin(), SortedSlots.end(),
|
|
[this](int LHS, int RHS) {
|
|
// We use -1 to denote a uninteresting slot. Place these slots at the end.
|
|
if (LHS == -1) return false;
|
|
if (RHS == -1) return true;
|
|
// Sort according to size.
|
|
return MFI->getObjectSize(LHS) > MFI->getObjectSize(RHS);
|
|
});
|
|
|
|
bool Changed = true;
|
|
while (Changed) {
|
|
Changed = false;
|
|
for (unsigned I = 0; I < NumSlots; ++I) {
|
|
if (SortedSlots[I] == -1)
|
|
continue;
|
|
|
|
for (unsigned J=I+1; J < NumSlots; ++J) {
|
|
if (SortedSlots[J] == -1)
|
|
continue;
|
|
|
|
int FirstSlot = SortedSlots[I];
|
|
int SecondSlot = SortedSlots[J];
|
|
LiveInterval *First = &*Intervals[FirstSlot];
|
|
LiveInterval *Second = &*Intervals[SecondSlot];
|
|
assert (!First->empty() && !Second->empty() && "Found an empty range");
|
|
|
|
// Merge disjoint slots.
|
|
if (!First->overlaps(*Second)) {
|
|
Changed = true;
|
|
First->MergeSegmentsInAsValue(*Second, First->getValNumInfo(0));
|
|
SlotRemap[SecondSlot] = FirstSlot;
|
|
SortedSlots[J] = -1;
|
|
DEBUG(dbgs()<<"Merging #"<<FirstSlot<<" and slots #"<<
|
|
SecondSlot<<" together.\n");
|
|
unsigned MaxAlignment = std::max(MFI->getObjectAlignment(FirstSlot),
|
|
MFI->getObjectAlignment(SecondSlot));
|
|
|
|
assert(MFI->getObjectSize(FirstSlot) >=
|
|
MFI->getObjectSize(SecondSlot) &&
|
|
"Merging a small object into a larger one");
|
|
|
|
RemovedSlots+=1;
|
|
ReducedSize += MFI->getObjectSize(SecondSlot);
|
|
MFI->setObjectAlignment(FirstSlot, MaxAlignment);
|
|
MFI->RemoveStackObject(SecondSlot);
|
|
}
|
|
}
|
|
}
|
|
}// While changed.
|
|
|
|
// Record statistics.
|
|
StackSpaceSaved += ReducedSize;
|
|
StackSlotMerged += RemovedSlots;
|
|
DEBUG(dbgs()<<"Merge "<<RemovedSlots<<" slots. Saved "<<
|
|
ReducedSize<<" bytes\n");
|
|
|
|
// Scan the entire function and update all machine operands that use frame
|
|
// indices to use the remapped frame index.
|
|
expungeSlotMap(SlotRemap, NumSlots);
|
|
remapInstructions(SlotRemap);
|
|
|
|
return removeAllMarkers();
|
|
}
|