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@165402 91177308-0d34-0410-b5e6-96231b3b80d8
2062 lines
78 KiB
C++
2062 lines
78 KiB
C++
//===-- ARMConstantIslandPass.cpp - ARM constant islands ------------------===//
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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 file contains a pass that splits the constant pool up into 'islands'
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// which are scattered through-out the function. This is required due to the
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// limited pc-relative displacements that ARM has.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "arm-cp-islands"
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#include "ARM.h"
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#include "ARMMachineFunctionInfo.h"
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#include "Thumb2InstrInfo.h"
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#include "MCTargetDesc/ARMAddressingModes.h"
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#include "llvm/CodeGen/MachineConstantPool.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineJumpTableInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/DataLayout.h"
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#include "llvm/Target/TargetMachine.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/Format.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/CommandLine.h"
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#include <algorithm>
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using namespace llvm;
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STATISTIC(NumCPEs, "Number of constpool entries");
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STATISTIC(NumSplit, "Number of uncond branches inserted");
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STATISTIC(NumCBrFixed, "Number of cond branches fixed");
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STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
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STATISTIC(NumTBs, "Number of table branches generated");
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STATISTIC(NumT2CPShrunk, "Number of Thumb2 constantpool instructions shrunk");
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STATISTIC(NumT2BrShrunk, "Number of Thumb2 immediate branches shrunk");
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STATISTIC(NumCBZ, "Number of CBZ / CBNZ formed");
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STATISTIC(NumJTMoved, "Number of jump table destination blocks moved");
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STATISTIC(NumJTInserted, "Number of jump table intermediate blocks inserted");
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static cl::opt<bool>
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AdjustJumpTableBlocks("arm-adjust-jump-tables", cl::Hidden, cl::init(true),
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cl::desc("Adjust basic block layout to better use TB[BH]"));
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// FIXME: This option should be removed once it has received sufficient testing.
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static cl::opt<bool>
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AlignConstantIslands("arm-align-constant-islands", cl::Hidden, cl::init(true),
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cl::desc("Align constant islands in code"));
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/// UnknownPadding - Return the worst case padding that could result from
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/// unknown offset bits. This does not include alignment padding caused by
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/// known offset bits.
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///
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/// @param LogAlign log2(alignment)
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/// @param KnownBits Number of known low offset bits.
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static inline unsigned UnknownPadding(unsigned LogAlign, unsigned KnownBits) {
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if (KnownBits < LogAlign)
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return (1u << LogAlign) - (1u << KnownBits);
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return 0;
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}
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namespace {
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/// ARMConstantIslands - Due to limited PC-relative displacements, ARM
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/// requires constant pool entries to be scattered among the instructions
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/// inside a function. To do this, it completely ignores the normal LLVM
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/// constant pool; instead, it places constants wherever it feels like with
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/// special instructions.
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///
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/// The terminology used in this pass includes:
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/// Islands - Clumps of constants placed in the function.
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/// Water - Potential places where an island could be formed.
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/// CPE - A constant pool entry that has been placed somewhere, which
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/// tracks a list of users.
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class ARMConstantIslands : public MachineFunctionPass {
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/// BasicBlockInfo - Information about the offset and size of a single
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/// basic block.
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struct BasicBlockInfo {
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/// Offset - Distance from the beginning of the function to the beginning
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/// of this basic block.
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///
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/// Offsets are computed assuming worst case padding before an aligned
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/// block. This means that subtracting basic block offsets always gives a
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/// conservative estimate of the real distance which may be smaller.
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///
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/// Because worst case padding is used, the computed offset of an aligned
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/// block may not actually be aligned.
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unsigned Offset;
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/// Size - Size of the basic block in bytes. If the block contains
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/// inline assembly, this is a worst case estimate.
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///
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/// The size does not include any alignment padding whether from the
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/// beginning of the block, or from an aligned jump table at the end.
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unsigned Size;
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/// KnownBits - The number of low bits in Offset that are known to be
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/// exact. The remaining bits of Offset are an upper bound.
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uint8_t KnownBits;
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/// Unalign - When non-zero, the block contains instructions (inline asm)
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/// of unknown size. The real size may be smaller than Size bytes by a
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/// multiple of 1 << Unalign.
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uint8_t Unalign;
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/// PostAlign - When non-zero, the block terminator contains a .align
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/// directive, so the end of the block is aligned to 1 << PostAlign
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/// bytes.
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uint8_t PostAlign;
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BasicBlockInfo() : Offset(0), Size(0), KnownBits(0), Unalign(0),
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PostAlign(0) {}
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/// Compute the number of known offset bits internally to this block.
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/// This number should be used to predict worst case padding when
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/// splitting the block.
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unsigned internalKnownBits() const {
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unsigned Bits = Unalign ? Unalign : KnownBits;
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// If the block size isn't a multiple of the known bits, assume the
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// worst case padding.
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if (Size & ((1u << Bits) - 1))
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Bits = CountTrailingZeros_32(Size);
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return Bits;
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}
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/// Compute the offset immediately following this block. If LogAlign is
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/// specified, return the offset the successor block will get if it has
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/// this alignment.
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unsigned postOffset(unsigned LogAlign = 0) const {
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unsigned PO = Offset + Size;
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unsigned LA = std::max(unsigned(PostAlign), LogAlign);
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if (!LA)
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return PO;
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// Add alignment padding from the terminator.
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return PO + UnknownPadding(LA, internalKnownBits());
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}
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/// Compute the number of known low bits of postOffset. If this block
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/// contains inline asm, the number of known bits drops to the
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/// instruction alignment. An aligned terminator may increase the number
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/// of know bits.
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/// If LogAlign is given, also consider the alignment of the next block.
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unsigned postKnownBits(unsigned LogAlign = 0) const {
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return std::max(std::max(unsigned(PostAlign), LogAlign),
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internalKnownBits());
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}
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};
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std::vector<BasicBlockInfo> BBInfo;
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/// WaterList - A sorted list of basic blocks where islands could be placed
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/// (i.e. blocks that don't fall through to the following block, due
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/// to a return, unreachable, or unconditional branch).
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std::vector<MachineBasicBlock*> WaterList;
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/// NewWaterList - The subset of WaterList that was created since the
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/// previous iteration by inserting unconditional branches.
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SmallSet<MachineBasicBlock*, 4> NewWaterList;
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typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
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/// CPUser - One user of a constant pool, keeping the machine instruction
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/// pointer, the constant pool being referenced, and the max displacement
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/// allowed from the instruction to the CP. The HighWaterMark records the
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/// highest basic block where a new CPEntry can be placed. To ensure this
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/// pass terminates, the CP entries are initially placed at the end of the
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/// function and then move monotonically to lower addresses. The
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/// exception to this rule is when the current CP entry for a particular
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/// CPUser is out of range, but there is another CP entry for the same
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/// constant value in range. We want to use the existing in-range CP
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/// entry, but if it later moves out of range, the search for new water
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/// should resume where it left off. The HighWaterMark is used to record
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/// that point.
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struct CPUser {
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MachineInstr *MI;
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MachineInstr *CPEMI;
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MachineBasicBlock *HighWaterMark;
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private:
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unsigned MaxDisp;
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public:
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bool NegOk;
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bool IsSoImm;
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bool KnownAlignment;
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CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
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bool neg, bool soimm)
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: MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), NegOk(neg), IsSoImm(soimm),
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KnownAlignment(false) {
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HighWaterMark = CPEMI->getParent();
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}
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/// getMaxDisp - Returns the maximum displacement supported by MI.
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/// Correct for unknown alignment.
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/// Conservatively subtract 2 bytes to handle weird alignment effects.
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unsigned getMaxDisp() const {
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return (KnownAlignment ? MaxDisp : MaxDisp - 2) - 2;
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}
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};
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/// CPUsers - Keep track of all of the machine instructions that use various
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/// constant pools and their max displacement.
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std::vector<CPUser> CPUsers;
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/// CPEntry - One per constant pool entry, keeping the machine instruction
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/// pointer, the constpool index, and the number of CPUser's which
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/// reference this entry.
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struct CPEntry {
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MachineInstr *CPEMI;
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unsigned CPI;
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unsigned RefCount;
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CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
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: CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
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};
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/// CPEntries - Keep track of all of the constant pool entry machine
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/// instructions. For each original constpool index (i.e. those that
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/// existed upon entry to this pass), it keeps a vector of entries.
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/// Original elements are cloned as we go along; the clones are
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/// put in the vector of the original element, but have distinct CPIs.
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std::vector<std::vector<CPEntry> > CPEntries;
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/// ImmBranch - One per immediate branch, keeping the machine instruction
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/// pointer, conditional or unconditional, the max displacement,
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/// and (if isCond is true) the corresponding unconditional branch
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/// opcode.
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struct ImmBranch {
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MachineInstr *MI;
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unsigned MaxDisp : 31;
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bool isCond : 1;
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int UncondBr;
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ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
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: MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
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};
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/// ImmBranches - Keep track of all the immediate branch instructions.
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///
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std::vector<ImmBranch> ImmBranches;
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/// PushPopMIs - Keep track of all the Thumb push / pop instructions.
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///
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SmallVector<MachineInstr*, 4> PushPopMIs;
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/// T2JumpTables - Keep track of all the Thumb2 jumptable instructions.
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SmallVector<MachineInstr*, 4> T2JumpTables;
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/// HasFarJump - True if any far jump instruction has been emitted during
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/// the branch fix up pass.
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bool HasFarJump;
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MachineFunction *MF;
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MachineConstantPool *MCP;
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const ARMBaseInstrInfo *TII;
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const ARMSubtarget *STI;
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ARMFunctionInfo *AFI;
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bool isThumb;
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bool isThumb1;
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bool isThumb2;
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public:
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static char ID;
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ARMConstantIslands() : MachineFunctionPass(ID) {}
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virtual bool runOnMachineFunction(MachineFunction &MF);
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virtual const char *getPassName() const {
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return "ARM constant island placement and branch shortening pass";
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}
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private:
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void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
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CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
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unsigned getCPELogAlign(const MachineInstr *CPEMI);
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void scanFunctionJumpTables();
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void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
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MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI);
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void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
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void adjustBBOffsetsAfter(MachineBasicBlock *BB);
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bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
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int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
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bool findAvailableWater(CPUser&U, unsigned UserOffset,
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water_iterator &WaterIter);
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void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
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MachineBasicBlock *&NewMBB);
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bool handleConstantPoolUser(unsigned CPUserIndex);
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void removeDeadCPEMI(MachineInstr *CPEMI);
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bool removeUnusedCPEntries();
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bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
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MachineInstr *CPEMI, unsigned Disp, bool NegOk,
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bool DoDump = false);
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bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
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CPUser &U, unsigned &Growth);
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bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
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bool fixupImmediateBr(ImmBranch &Br);
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bool fixupConditionalBr(ImmBranch &Br);
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bool fixupUnconditionalBr(ImmBranch &Br);
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bool undoLRSpillRestore();
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bool mayOptimizeThumb2Instruction(const MachineInstr *MI) const;
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bool optimizeThumb2Instructions();
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bool optimizeThumb2Branches();
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bool reorderThumb2JumpTables();
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bool optimizeThumb2JumpTables();
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MachineBasicBlock *adjustJTTargetBlockForward(MachineBasicBlock *BB,
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MachineBasicBlock *JTBB);
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void computeBlockSize(MachineBasicBlock *MBB);
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unsigned getOffsetOf(MachineInstr *MI) const;
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unsigned getUserOffset(CPUser&) const;
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void dumpBBs();
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void verify();
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bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
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unsigned Disp, bool NegativeOK, bool IsSoImm = false);
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bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
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const CPUser &U) {
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return isOffsetInRange(UserOffset, TrialOffset,
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U.getMaxDisp(), U.NegOk, U.IsSoImm);
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}
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};
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char ARMConstantIslands::ID = 0;
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}
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/// verify - check BBOffsets, BBSizes, alignment of islands
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void ARMConstantIslands::verify() {
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#ifndef NDEBUG
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for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
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MBBI != E; ++MBBI) {
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MachineBasicBlock *MBB = MBBI;
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unsigned MBBId = MBB->getNumber();
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assert(!MBBId || BBInfo[MBBId - 1].postOffset() <= BBInfo[MBBId].Offset);
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}
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DEBUG(dbgs() << "Verifying " << CPUsers.size() << " CP users.\n");
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for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) {
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CPUser &U = CPUsers[i];
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unsigned UserOffset = getUserOffset(U);
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// Verify offset using the real max displacement without the safety
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// adjustment.
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if (isCPEntryInRange(U.MI, UserOffset, U.CPEMI, U.getMaxDisp()+2, U.NegOk,
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/* DoDump = */ true)) {
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DEBUG(dbgs() << "OK\n");
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continue;
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}
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DEBUG(dbgs() << "Out of range.\n");
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dumpBBs();
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DEBUG(MF->dump());
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llvm_unreachable("Constant pool entry out of range!");
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}
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#endif
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}
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/// print block size and offset information - debugging
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void ARMConstantIslands::dumpBBs() {
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DEBUG({
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for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
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const BasicBlockInfo &BBI = BBInfo[J];
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dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
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<< " kb=" << unsigned(BBI.KnownBits)
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<< " ua=" << unsigned(BBI.Unalign)
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<< " pa=" << unsigned(BBI.PostAlign)
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<< format(" size=%#x\n", BBInfo[J].Size);
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}
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});
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}
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/// createARMConstantIslandPass - returns an instance of the constpool
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/// island pass.
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FunctionPass *llvm::createARMConstantIslandPass() {
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return new ARMConstantIslands();
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}
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bool ARMConstantIslands::runOnMachineFunction(MachineFunction &mf) {
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MF = &mf;
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MCP = mf.getConstantPool();
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DEBUG(dbgs() << "***** ARMConstantIslands: "
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<< MCP->getConstants().size() << " CP entries, aligned to "
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<< MCP->getConstantPoolAlignment() << " bytes *****\n");
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TII = (const ARMBaseInstrInfo*)MF->getTarget().getInstrInfo();
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AFI = MF->getInfo<ARMFunctionInfo>();
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STI = &MF->getTarget().getSubtarget<ARMSubtarget>();
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isThumb = AFI->isThumbFunction();
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isThumb1 = AFI->isThumb1OnlyFunction();
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isThumb2 = AFI->isThumb2Function();
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HasFarJump = false;
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// This pass invalidates liveness information when it splits basic blocks.
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MF->getRegInfo().invalidateLiveness();
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// Renumber all of the machine basic blocks in the function, guaranteeing that
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// the numbers agree with the position of the block in the function.
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MF->RenumberBlocks();
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// Try to reorder and otherwise adjust the block layout to make good use
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// of the TB[BH] instructions.
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bool MadeChange = false;
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if (isThumb2 && AdjustJumpTableBlocks) {
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scanFunctionJumpTables();
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MadeChange |= reorderThumb2JumpTables();
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// Data is out of date, so clear it. It'll be re-computed later.
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T2JumpTables.clear();
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// Blocks may have shifted around. Keep the numbering up to date.
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MF->RenumberBlocks();
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}
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// Thumb1 functions containing constant pools get 4-byte alignment.
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// This is so we can keep exact track of where the alignment padding goes.
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// ARM and Thumb2 functions need to be 4-byte aligned.
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if (!isThumb1)
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MF->ensureAlignment(2); // 2 = log2(4)
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// Perform the initial placement of the constant pool entries. To start with,
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// we put them all at the end of the function.
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std::vector<MachineInstr*> CPEMIs;
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if (!MCP->isEmpty())
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doInitialPlacement(CPEMIs);
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/// The next UID to take is the first unused one.
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AFI->initPICLabelUId(CPEMIs.size());
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// Do the initial scan of the function, building up information about the
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// sizes of each block, the location of all the water, and finding all of the
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// constant pool users.
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initializeFunctionInfo(CPEMIs);
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CPEMIs.clear();
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DEBUG(dumpBBs());
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/// Remove dead constant pool entries.
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MadeChange |= removeUnusedCPEntries();
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// Iteratively place constant pool entries and fix up branches until there
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// is no change.
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unsigned NoCPIters = 0, NoBRIters = 0;
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while (true) {
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DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
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bool CPChange = false;
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for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
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CPChange |= handleConstantPoolUser(i);
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if (CPChange && ++NoCPIters > 30)
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report_fatal_error("Constant Island pass failed to converge!");
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DEBUG(dumpBBs());
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// Clear NewWaterList now. If we split a block for branches, it should
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// appear as "new water" for the next iteration of constant pool placement.
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NewWaterList.clear();
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DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
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bool BRChange = false;
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for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
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BRChange |= fixupImmediateBr(ImmBranches[i]);
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if (BRChange && ++NoBRIters > 30)
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report_fatal_error("Branch Fix Up pass failed to converge!");
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DEBUG(dumpBBs());
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if (!CPChange && !BRChange)
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break;
|
|
MadeChange = true;
|
|
}
|
|
|
|
// Shrink 32-bit Thumb2 branch, load, and store instructions.
|
|
if (isThumb2 && !STI->prefers32BitThumb())
|
|
MadeChange |= optimizeThumb2Instructions();
|
|
|
|
// After a while, this might be made debug-only, but it is not expensive.
|
|
verify();
|
|
|
|
// If LR has been forced spilled and no far jump (i.e. BL) has been issued,
|
|
// undo the spill / restore of LR if possible.
|
|
if (isThumb && !HasFarJump && AFI->isLRSpilledForFarJump())
|
|
MadeChange |= undoLRSpillRestore();
|
|
|
|
// Save the mapping between original and cloned constpool entries.
|
|
for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
|
|
for (unsigned j = 0, je = CPEntries[i].size(); j != je; ++j) {
|
|
const CPEntry & CPE = CPEntries[i][j];
|
|
AFI->recordCPEClone(i, CPE.CPI);
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << '\n'; dumpBBs());
|
|
|
|
BBInfo.clear();
|
|
WaterList.clear();
|
|
CPUsers.clear();
|
|
CPEntries.clear();
|
|
ImmBranches.clear();
|
|
PushPopMIs.clear();
|
|
T2JumpTables.clear();
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
/// doInitialPlacement - Perform the initial placement of the constant pool
|
|
/// entries. To start with, we put them all at the end of the function.
|
|
void
|
|
ARMConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
|
|
// Create the basic block to hold the CPE's.
|
|
MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
|
|
MF->push_back(BB);
|
|
|
|
// MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
|
|
unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
|
|
|
|
// Mark the basic block as required by the const-pool.
|
|
// If AlignConstantIslands isn't set, use 4-byte alignment for everything.
|
|
BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
|
|
|
|
// The function needs to be as aligned as the basic blocks. The linker may
|
|
// move functions around based on their alignment.
|
|
MF->ensureAlignment(BB->getAlignment());
|
|
|
|
// Order the entries in BB by descending alignment. That ensures correct
|
|
// alignment of all entries as long as BB is sufficiently aligned. Keep
|
|
// track of the insertion point for each alignment. We are going to bucket
|
|
// sort the entries as they are created.
|
|
SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
|
|
|
|
// Add all of the constants from the constant pool to the end block, use an
|
|
// identity mapping of CPI's to CPE's.
|
|
const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
|
|
|
|
const DataLayout &TD = *MF->getTarget().getDataLayout();
|
|
for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
|
|
unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
|
|
assert(Size >= 4 && "Too small constant pool entry");
|
|
unsigned Align = CPs[i].getAlignment();
|
|
assert(isPowerOf2_32(Align) && "Invalid alignment");
|
|
// Verify that all constant pool entries are a multiple of their alignment.
|
|
// If not, we would have to pad them out so that instructions stay aligned.
|
|
assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
|
|
|
|
// Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
|
|
unsigned LogAlign = Log2_32(Align);
|
|
MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
|
|
MachineInstr *CPEMI =
|
|
BuildMI(*BB, InsAt, DebugLoc(), TII->get(ARM::CONSTPOOL_ENTRY))
|
|
.addImm(i).addConstantPoolIndex(i).addImm(Size);
|
|
CPEMIs.push_back(CPEMI);
|
|
|
|
// Ensure that future entries with higher alignment get inserted before
|
|
// CPEMI. This is bucket sort with iterators.
|
|
for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
|
|
if (InsPoint[a] == InsAt)
|
|
InsPoint[a] = CPEMI;
|
|
|
|
// Add a new CPEntry, but no corresponding CPUser yet.
|
|
std::vector<CPEntry> CPEs;
|
|
CPEs.push_back(CPEntry(CPEMI, i));
|
|
CPEntries.push_back(CPEs);
|
|
++NumCPEs;
|
|
DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
|
|
<< Size << ", align = " << Align <<'\n');
|
|
}
|
|
DEBUG(BB->dump());
|
|
}
|
|
|
|
/// BBHasFallthrough - Return true if the specified basic block can fallthrough
|
|
/// into the block immediately after it.
|
|
static bool BBHasFallthrough(MachineBasicBlock *MBB) {
|
|
// Get the next machine basic block in the function.
|
|
MachineFunction::iterator MBBI = MBB;
|
|
// Can't fall off end of function.
|
|
if (llvm::next(MBBI) == MBB->getParent()->end())
|
|
return false;
|
|
|
|
MachineBasicBlock *NextBB = llvm::next(MBBI);
|
|
for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
|
|
E = MBB->succ_end(); I != E; ++I)
|
|
if (*I == NextBB)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
|
|
/// look up the corresponding CPEntry.
|
|
ARMConstantIslands::CPEntry
|
|
*ARMConstantIslands::findConstPoolEntry(unsigned CPI,
|
|
const MachineInstr *CPEMI) {
|
|
std::vector<CPEntry> &CPEs = CPEntries[CPI];
|
|
// Number of entries per constpool index should be small, just do a
|
|
// linear search.
|
|
for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
|
|
if (CPEs[i].CPEMI == CPEMI)
|
|
return &CPEs[i];
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/// getCPELogAlign - Returns the required alignment of the constant pool entry
|
|
/// represented by CPEMI. Alignment is measured in log2(bytes) units.
|
|
unsigned ARMConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) {
|
|
assert(CPEMI && CPEMI->getOpcode() == ARM::CONSTPOOL_ENTRY);
|
|
|
|
// Everything is 4-byte aligned unless AlignConstantIslands is set.
|
|
if (!AlignConstantIslands)
|
|
return 2;
|
|
|
|
unsigned CPI = CPEMI->getOperand(1).getIndex();
|
|
assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
|
|
unsigned Align = MCP->getConstants()[CPI].getAlignment();
|
|
assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
|
|
return Log2_32(Align);
|
|
}
|
|
|
|
/// scanFunctionJumpTables - Do a scan of the function, building up
|
|
/// information about the sizes of each block and the locations of all
|
|
/// the jump tables.
|
|
void ARMConstantIslands::scanFunctionJumpTables() {
|
|
for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
|
|
MBBI != E; ++MBBI) {
|
|
MachineBasicBlock &MBB = *MBBI;
|
|
|
|
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
|
|
I != E; ++I)
|
|
if (I->isBranch() && I->getOpcode() == ARM::t2BR_JT)
|
|
T2JumpTables.push_back(I);
|
|
}
|
|
}
|
|
|
|
/// initializeFunctionInfo - Do the initial scan of the function, building up
|
|
/// information about the sizes of each block, the location of all the water,
|
|
/// and finding all of the constant pool users.
|
|
void ARMConstantIslands::
|
|
initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
|
|
BBInfo.clear();
|
|
BBInfo.resize(MF->getNumBlockIDs());
|
|
|
|
// First thing, compute the size of all basic blocks, and see if the function
|
|
// has any inline assembly in it. If so, we have to be conservative about
|
|
// alignment assumptions, as we don't know for sure the size of any
|
|
// instructions in the inline assembly.
|
|
for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
|
|
computeBlockSize(I);
|
|
|
|
// The known bits of the entry block offset are determined by the function
|
|
// alignment.
|
|
BBInfo.front().KnownBits = MF->getAlignment();
|
|
|
|
// Compute block offsets and known bits.
|
|
adjustBBOffsetsAfter(MF->begin());
|
|
|
|
// Now go back through the instructions and build up our data structures.
|
|
for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end();
|
|
MBBI != E; ++MBBI) {
|
|
MachineBasicBlock &MBB = *MBBI;
|
|
|
|
// If this block doesn't fall through into the next MBB, then this is
|
|
// 'water' that a constant pool island could be placed.
|
|
if (!BBHasFallthrough(&MBB))
|
|
WaterList.push_back(&MBB);
|
|
|
|
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
|
|
I != E; ++I) {
|
|
if (I->isDebugValue())
|
|
continue;
|
|
|
|
int Opc = I->getOpcode();
|
|
if (I->isBranch()) {
|
|
bool isCond = false;
|
|
unsigned Bits = 0;
|
|
unsigned Scale = 1;
|
|
int UOpc = Opc;
|
|
switch (Opc) {
|
|
default:
|
|
continue; // Ignore other JT branches
|
|
case ARM::t2BR_JT:
|
|
T2JumpTables.push_back(I);
|
|
continue; // Does not get an entry in ImmBranches
|
|
case ARM::Bcc:
|
|
isCond = true;
|
|
UOpc = ARM::B;
|
|
// Fallthrough
|
|
case ARM::B:
|
|
Bits = 24;
|
|
Scale = 4;
|
|
break;
|
|
case ARM::tBcc:
|
|
isCond = true;
|
|
UOpc = ARM::tB;
|
|
Bits = 8;
|
|
Scale = 2;
|
|
break;
|
|
case ARM::tB:
|
|
Bits = 11;
|
|
Scale = 2;
|
|
break;
|
|
case ARM::t2Bcc:
|
|
isCond = true;
|
|
UOpc = ARM::t2B;
|
|
Bits = 20;
|
|
Scale = 2;
|
|
break;
|
|
case ARM::t2B:
|
|
Bits = 24;
|
|
Scale = 2;
|
|
break;
|
|
}
|
|
|
|
// Record this immediate branch.
|
|
unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
|
|
ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
|
|
}
|
|
|
|
if (Opc == ARM::tPUSH || Opc == ARM::tPOP_RET)
|
|
PushPopMIs.push_back(I);
|
|
|
|
if (Opc == ARM::CONSTPOOL_ENTRY)
|
|
continue;
|
|
|
|
// Scan the instructions for constant pool operands.
|
|
for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
|
|
if (I->getOperand(op).isCPI()) {
|
|
// We found one. The addressing mode tells us the max displacement
|
|
// from the PC that this instruction permits.
|
|
|
|
// Basic size info comes from the TSFlags field.
|
|
unsigned Bits = 0;
|
|
unsigned Scale = 1;
|
|
bool NegOk = false;
|
|
bool IsSoImm = false;
|
|
|
|
switch (Opc) {
|
|
default:
|
|
llvm_unreachable("Unknown addressing mode for CP reference!");
|
|
|
|
// Taking the address of a CP entry.
|
|
case ARM::LEApcrel:
|
|
// This takes a SoImm, which is 8 bit immediate rotated. We'll
|
|
// pretend the maximum offset is 255 * 4. Since each instruction
|
|
// 4 byte wide, this is always correct. We'll check for other
|
|
// displacements that fits in a SoImm as well.
|
|
Bits = 8;
|
|
Scale = 4;
|
|
NegOk = true;
|
|
IsSoImm = true;
|
|
break;
|
|
case ARM::t2LEApcrel:
|
|
Bits = 12;
|
|
NegOk = true;
|
|
break;
|
|
case ARM::tLEApcrel:
|
|
Bits = 8;
|
|
Scale = 4;
|
|
break;
|
|
|
|
case ARM::LDRi12:
|
|
case ARM::LDRcp:
|
|
case ARM::t2LDRpci:
|
|
Bits = 12; // +-offset_12
|
|
NegOk = true;
|
|
break;
|
|
|
|
case ARM::tLDRpci:
|
|
Bits = 8;
|
|
Scale = 4; // +(offset_8*4)
|
|
break;
|
|
|
|
case ARM::VLDRD:
|
|
case ARM::VLDRS:
|
|
Bits = 8;
|
|
Scale = 4; // +-(offset_8*4)
|
|
NegOk = true;
|
|
break;
|
|
}
|
|
|
|
// Remember that this is a user of a CP entry.
|
|
unsigned CPI = I->getOperand(op).getIndex();
|
|
MachineInstr *CPEMI = CPEMIs[CPI];
|
|
unsigned MaxOffs = ((1 << Bits)-1) * Scale;
|
|
CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk, IsSoImm));
|
|
|
|
// Increment corresponding CPEntry reference count.
|
|
CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
|
|
assert(CPE && "Cannot find a corresponding CPEntry!");
|
|
CPE->RefCount++;
|
|
|
|
// Instructions can only use one CP entry, don't bother scanning the
|
|
// rest of the operands.
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// computeBlockSize - Compute the size and some alignment information for MBB.
|
|
/// This function updates BBInfo directly.
|
|
void ARMConstantIslands::computeBlockSize(MachineBasicBlock *MBB) {
|
|
BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
|
|
BBI.Size = 0;
|
|
BBI.Unalign = 0;
|
|
BBI.PostAlign = 0;
|
|
|
|
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
|
|
++I) {
|
|
BBI.Size += TII->GetInstSizeInBytes(I);
|
|
// For inline asm, GetInstSizeInBytes returns a conservative estimate.
|
|
// The actual size may be smaller, but still a multiple of the instr size.
|
|
if (I->isInlineAsm())
|
|
BBI.Unalign = isThumb ? 1 : 2;
|
|
// Also consider instructions that may be shrunk later.
|
|
else if (isThumb && mayOptimizeThumb2Instruction(I))
|
|
BBI.Unalign = 1;
|
|
}
|
|
|
|
// tBR_JTr contains a .align 2 directive.
|
|
if (!MBB->empty() && MBB->back().getOpcode() == ARM::tBR_JTr) {
|
|
BBI.PostAlign = 2;
|
|
MBB->getParent()->ensureAlignment(2);
|
|
}
|
|
}
|
|
|
|
/// getOffsetOf - Return the current offset of the specified machine instruction
|
|
/// from the start of the function. This offset changes as stuff is moved
|
|
/// around inside the function.
|
|
unsigned ARMConstantIslands::getOffsetOf(MachineInstr *MI) const {
|
|
MachineBasicBlock *MBB = MI->getParent();
|
|
|
|
// The offset is composed of two things: the sum of the sizes of all MBB's
|
|
// before this instruction's block, and the offset from the start of the block
|
|
// it is in.
|
|
unsigned Offset = BBInfo[MBB->getNumber()].Offset;
|
|
|
|
// Sum instructions before MI in MBB.
|
|
for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
|
|
assert(I != MBB->end() && "Didn't find MI in its own basic block?");
|
|
Offset += TII->GetInstSizeInBytes(I);
|
|
}
|
|
return Offset;
|
|
}
|
|
|
|
/// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
|
|
/// ID.
|
|
static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
|
|
const MachineBasicBlock *RHS) {
|
|
return LHS->getNumber() < RHS->getNumber();
|
|
}
|
|
|
|
/// updateForInsertedWaterBlock - When a block is newly inserted into the
|
|
/// machine function, it upsets all of the block numbers. Renumber the blocks
|
|
/// and update the arrays that parallel this numbering.
|
|
void ARMConstantIslands::updateForInsertedWaterBlock(MachineBasicBlock *NewBB) {
|
|
// Renumber the MBB's to keep them consecutive.
|
|
NewBB->getParent()->RenumberBlocks(NewBB);
|
|
|
|
// Insert an entry into BBInfo to align it properly with the (newly
|
|
// renumbered) block numbers.
|
|
BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
|
|
|
|
// Next, update WaterList. Specifically, we need to add NewMBB as having
|
|
// available water after it.
|
|
water_iterator IP =
|
|
std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
|
|
CompareMBBNumbers);
|
|
WaterList.insert(IP, NewBB);
|
|
}
|
|
|
|
|
|
/// Split the basic block containing MI into two blocks, which are joined by
|
|
/// an unconditional branch. Update data structures and renumber blocks to
|
|
/// account for this change and returns the newly created block.
|
|
MachineBasicBlock *ARMConstantIslands::splitBlockBeforeInstr(MachineInstr *MI) {
|
|
MachineBasicBlock *OrigBB = MI->getParent();
|
|
|
|
// Create a new MBB for the code after the OrigBB.
|
|
MachineBasicBlock *NewBB =
|
|
MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
|
|
MachineFunction::iterator MBBI = OrigBB; ++MBBI;
|
|
MF->insert(MBBI, NewBB);
|
|
|
|
// Splice the instructions starting with MI over to NewBB.
|
|
NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
|
|
|
|
// Add an unconditional branch from OrigBB to NewBB.
|
|
// Note the new unconditional branch is not being recorded.
|
|
// There doesn't seem to be meaningful DebugInfo available; this doesn't
|
|
// correspond to anything in the source.
|
|
unsigned Opc = isThumb ? (isThumb2 ? ARM::t2B : ARM::tB) : ARM::B;
|
|
if (!isThumb)
|
|
BuildMI(OrigBB, DebugLoc(), TII->get(Opc)).addMBB(NewBB);
|
|
else
|
|
BuildMI(OrigBB, DebugLoc(), TII->get(Opc)).addMBB(NewBB)
|
|
.addImm(ARMCC::AL).addReg(0);
|
|
++NumSplit;
|
|
|
|
// Update the CFG. All succs of OrigBB are now succs of NewBB.
|
|
NewBB->transferSuccessors(OrigBB);
|
|
|
|
// OrigBB branches to NewBB.
|
|
OrigBB->addSuccessor(NewBB);
|
|
|
|
// Update internal data structures to account for the newly inserted MBB.
|
|
// This is almost the same as updateForInsertedWaterBlock, except that
|
|
// the Water goes after OrigBB, not NewBB.
|
|
MF->RenumberBlocks(NewBB);
|
|
|
|
// Insert an entry into BBInfo to align it properly with the (newly
|
|
// renumbered) block numbers.
|
|
BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
|
|
|
|
// Next, update WaterList. Specifically, we need to add OrigMBB as having
|
|
// available water after it (but not if it's already there, which happens
|
|
// when splitting before a conditional branch that is followed by an
|
|
// unconditional branch - in that case we want to insert NewBB).
|
|
water_iterator IP =
|
|
std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
|
|
CompareMBBNumbers);
|
|
MachineBasicBlock* WaterBB = *IP;
|
|
if (WaterBB == OrigBB)
|
|
WaterList.insert(llvm::next(IP), NewBB);
|
|
else
|
|
WaterList.insert(IP, OrigBB);
|
|
NewWaterList.insert(OrigBB);
|
|
|
|
// Figure out how large the OrigBB is. As the first half of the original
|
|
// block, it cannot contain a tablejump. The size includes
|
|
// the new jump we added. (It should be possible to do this without
|
|
// recounting everything, but it's very confusing, and this is rarely
|
|
// executed.)
|
|
computeBlockSize(OrigBB);
|
|
|
|
// Figure out how large the NewMBB is. As the second half of the original
|
|
// block, it may contain a tablejump.
|
|
computeBlockSize(NewBB);
|
|
|
|
// All BBOffsets following these blocks must be modified.
|
|
adjustBBOffsetsAfter(OrigBB);
|
|
|
|
return NewBB;
|
|
}
|
|
|
|
/// getUserOffset - Compute the offset of U.MI as seen by the hardware
|
|
/// displacement computation. Update U.KnownAlignment to match its current
|
|
/// basic block location.
|
|
unsigned ARMConstantIslands::getUserOffset(CPUser &U) const {
|
|
unsigned UserOffset = getOffsetOf(U.MI);
|
|
const BasicBlockInfo &BBI = BBInfo[U.MI->getParent()->getNumber()];
|
|
unsigned KnownBits = BBI.internalKnownBits();
|
|
|
|
// The value read from PC is offset from the actual instruction address.
|
|
UserOffset += (isThumb ? 4 : 8);
|
|
|
|
// Because of inline assembly, we may not know the alignment (mod 4) of U.MI.
|
|
// Make sure U.getMaxDisp() returns a constrained range.
|
|
U.KnownAlignment = (KnownBits >= 2);
|
|
|
|
// On Thumb, offsets==2 mod 4 are rounded down by the hardware for
|
|
// purposes of the displacement computation; compensate for that here.
|
|
// For unknown alignments, getMaxDisp() constrains the range instead.
|
|
if (isThumb && U.KnownAlignment)
|
|
UserOffset &= ~3u;
|
|
|
|
return UserOffset;
|
|
}
|
|
|
|
/// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
|
|
/// reference) is within MaxDisp of TrialOffset (a proposed location of a
|
|
/// constant pool entry).
|
|
/// UserOffset is computed by getUserOffset above to include PC adjustments. If
|
|
/// the mod 4 alignment of UserOffset is not known, the uncertainty must be
|
|
/// subtracted from MaxDisp instead. CPUser::getMaxDisp() does that.
|
|
bool ARMConstantIslands::isOffsetInRange(unsigned UserOffset,
|
|
unsigned TrialOffset, unsigned MaxDisp,
|
|
bool NegativeOK, bool IsSoImm) {
|
|
if (UserOffset <= TrialOffset) {
|
|
// User before the Trial.
|
|
if (TrialOffset - UserOffset <= MaxDisp)
|
|
return true;
|
|
// FIXME: Make use full range of soimm values.
|
|
} else if (NegativeOK) {
|
|
if (UserOffset - TrialOffset <= MaxDisp)
|
|
return true;
|
|
// FIXME: Make use full range of soimm values.
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// isWaterInRange - Returns true if a CPE placed after the specified
|
|
/// Water (a basic block) will be in range for the specific MI.
|
|
///
|
|
/// Compute how much the function will grow by inserting a CPE after Water.
|
|
bool ARMConstantIslands::isWaterInRange(unsigned UserOffset,
|
|
MachineBasicBlock* Water, CPUser &U,
|
|
unsigned &Growth) {
|
|
unsigned CPELogAlign = getCPELogAlign(U.CPEMI);
|
|
unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
|
|
unsigned NextBlockOffset, NextBlockAlignment;
|
|
MachineFunction::const_iterator NextBlock = Water;
|
|
if (++NextBlock == MF->end()) {
|
|
NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
|
|
NextBlockAlignment = 0;
|
|
} else {
|
|
NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
|
|
NextBlockAlignment = NextBlock->getAlignment();
|
|
}
|
|
unsigned Size = U.CPEMI->getOperand(2).getImm();
|
|
unsigned CPEEnd = CPEOffset + Size;
|
|
|
|
// The CPE may be able to hide in the alignment padding before the next
|
|
// block. It may also cause more padding to be required if it is more aligned
|
|
// that the next block.
|
|
if (CPEEnd > NextBlockOffset) {
|
|
Growth = CPEEnd - NextBlockOffset;
|
|
// Compute the padding that would go at the end of the CPE to align the next
|
|
// block.
|
|
Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment);
|
|
|
|
// If the CPE is to be inserted before the instruction, that will raise
|
|
// the offset of the instruction. Also account for unknown alignment padding
|
|
// in blocks between CPE and the user.
|
|
if (CPEOffset < UserOffset)
|
|
UserOffset += Growth + UnknownPadding(MF->getAlignment(), CPELogAlign);
|
|
} else
|
|
// CPE fits in existing padding.
|
|
Growth = 0;
|
|
|
|
return isOffsetInRange(UserOffset, CPEOffset, U);
|
|
}
|
|
|
|
/// isCPEntryInRange - Returns true if the distance between specific MI and
|
|
/// specific ConstPool entry instruction can fit in MI's displacement field.
|
|
bool ARMConstantIslands::isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
|
|
MachineInstr *CPEMI, unsigned MaxDisp,
|
|
bool NegOk, bool DoDump) {
|
|
unsigned CPEOffset = getOffsetOf(CPEMI);
|
|
|
|
if (DoDump) {
|
|
DEBUG({
|
|
unsigned Block = MI->getParent()->getNumber();
|
|
const BasicBlockInfo &BBI = BBInfo[Block];
|
|
dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
|
|
<< " max delta=" << MaxDisp
|
|
<< format(" insn address=%#x", UserOffset)
|
|
<< " in BB#" << Block << ": "
|
|
<< format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
|
|
<< format("CPE address=%#x offset=%+d: ", CPEOffset,
|
|
int(CPEOffset-UserOffset));
|
|
});
|
|
}
|
|
|
|
return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
|
|
/// unconditionally branches to its only successor.
|
|
static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
|
|
if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
|
|
return false;
|
|
|
|
MachineBasicBlock *Succ = *MBB->succ_begin();
|
|
MachineBasicBlock *Pred = *MBB->pred_begin();
|
|
MachineInstr *PredMI = &Pred->back();
|
|
if (PredMI->getOpcode() == ARM::B || PredMI->getOpcode() == ARM::tB
|
|
|| PredMI->getOpcode() == ARM::t2B)
|
|
return PredMI->getOperand(0).getMBB() == Succ;
|
|
return false;
|
|
}
|
|
#endif // NDEBUG
|
|
|
|
void ARMConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
|
|
unsigned BBNum = BB->getNumber();
|
|
for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
|
|
// Get the offset and known bits at the end of the layout predecessor.
|
|
// Include the alignment of the current block.
|
|
unsigned LogAlign = MF->getBlockNumbered(i)->getAlignment();
|
|
unsigned Offset = BBInfo[i - 1].postOffset(LogAlign);
|
|
unsigned KnownBits = BBInfo[i - 1].postKnownBits(LogAlign);
|
|
|
|
// This is where block i begins. Stop if the offset is already correct,
|
|
// and we have updated 2 blocks. This is the maximum number of blocks
|
|
// changed before calling this function.
|
|
if (i > BBNum + 2 &&
|
|
BBInfo[i].Offset == Offset &&
|
|
BBInfo[i].KnownBits == KnownBits)
|
|
break;
|
|
|
|
BBInfo[i].Offset = Offset;
|
|
BBInfo[i].KnownBits = KnownBits;
|
|
}
|
|
}
|
|
|
|
/// decrementCPEReferenceCount - find the constant pool entry with index CPI
|
|
/// and instruction CPEMI, and decrement its refcount. If the refcount
|
|
/// becomes 0 remove the entry and instruction. Returns true if we removed
|
|
/// the entry, false if we didn't.
|
|
|
|
bool ARMConstantIslands::decrementCPEReferenceCount(unsigned CPI,
|
|
MachineInstr *CPEMI) {
|
|
// Find the old entry. Eliminate it if it is no longer used.
|
|
CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
|
|
assert(CPE && "Unexpected!");
|
|
if (--CPE->RefCount == 0) {
|
|
removeDeadCPEMI(CPEMI);
|
|
CPE->CPEMI = NULL;
|
|
--NumCPEs;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// LookForCPEntryInRange - see if the currently referenced CPE is in range;
|
|
/// if not, see if an in-range clone of the CPE is in range, and if so,
|
|
/// change the data structures so the user references the clone. Returns:
|
|
/// 0 = no existing entry found
|
|
/// 1 = entry found, and there were no code insertions or deletions
|
|
/// 2 = entry found, and there were code insertions or deletions
|
|
int ARMConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
|
|
{
|
|
MachineInstr *UserMI = U.MI;
|
|
MachineInstr *CPEMI = U.CPEMI;
|
|
|
|
// Check to see if the CPE is already in-range.
|
|
if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
|
|
true)) {
|
|
DEBUG(dbgs() << "In range\n");
|
|
return 1;
|
|
}
|
|
|
|
// No. Look for previously created clones of the CPE that are in range.
|
|
unsigned CPI = CPEMI->getOperand(1).getIndex();
|
|
std::vector<CPEntry> &CPEs = CPEntries[CPI];
|
|
for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
|
|
// We already tried this one
|
|
if (CPEs[i].CPEMI == CPEMI)
|
|
continue;
|
|
// Removing CPEs can leave empty entries, skip
|
|
if (CPEs[i].CPEMI == NULL)
|
|
continue;
|
|
if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
|
|
U.NegOk)) {
|
|
DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
|
|
<< CPEs[i].CPI << "\n");
|
|
// Point the CPUser node to the replacement
|
|
U.CPEMI = CPEs[i].CPEMI;
|
|
// Change the CPI in the instruction operand to refer to the clone.
|
|
for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
|
|
if (UserMI->getOperand(j).isCPI()) {
|
|
UserMI->getOperand(j).setIndex(CPEs[i].CPI);
|
|
break;
|
|
}
|
|
// Adjust the refcount of the clone...
|
|
CPEs[i].RefCount++;
|
|
// ...and the original. If we didn't remove the old entry, none of the
|
|
// addresses changed, so we don't need another pass.
|
|
return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
|
|
/// the specific unconditional branch instruction.
|
|
static inline unsigned getUnconditionalBrDisp(int Opc) {
|
|
switch (Opc) {
|
|
case ARM::tB:
|
|
return ((1<<10)-1)*2;
|
|
case ARM::t2B:
|
|
return ((1<<23)-1)*2;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return ((1<<23)-1)*4;
|
|
}
|
|
|
|
/// findAvailableWater - Look for an existing entry in the WaterList in which
|
|
/// we can place the CPE referenced from U so it's within range of U's MI.
|
|
/// Returns true if found, false if not. If it returns true, WaterIter
|
|
/// is set to the WaterList entry. For Thumb, prefer water that will not
|
|
/// introduce padding to water that will. To ensure that this pass
|
|
/// terminates, the CPE location for a particular CPUser is only allowed to
|
|
/// move to a lower address, so search backward from the end of the list and
|
|
/// prefer the first water that is in range.
|
|
bool ARMConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
|
|
water_iterator &WaterIter) {
|
|
if (WaterList.empty())
|
|
return false;
|
|
|
|
unsigned BestGrowth = ~0u;
|
|
for (water_iterator IP = prior(WaterList.end()), B = WaterList.begin();;
|
|
--IP) {
|
|
MachineBasicBlock* WaterBB = *IP;
|
|
// Check if water is in range and is either at a lower address than the
|
|
// current "high water mark" or a new water block that was created since
|
|
// the previous iteration by inserting an unconditional branch. In the
|
|
// latter case, we want to allow resetting the high water mark back to
|
|
// this new water since we haven't seen it before. Inserting branches
|
|
// should be relatively uncommon and when it does happen, we want to be
|
|
// sure to take advantage of it for all the CPEs near that block, so that
|
|
// we don't insert more branches than necessary.
|
|
unsigned Growth;
|
|
if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
|
|
(WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
|
|
NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
|
|
// This is the least amount of required padding seen so far.
|
|
BestGrowth = Growth;
|
|
WaterIter = IP;
|
|
DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
|
|
<< " Growth=" << Growth << '\n');
|
|
|
|
// Keep looking unless it is perfect.
|
|
if (BestGrowth == 0)
|
|
return true;
|
|
}
|
|
if (IP == B)
|
|
break;
|
|
}
|
|
return BestGrowth != ~0u;
|
|
}
|
|
|
|
/// createNewWater - No existing WaterList entry will work for
|
|
/// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
|
|
/// block is used if in range, and the conditional branch munged so control
|
|
/// flow is correct. Otherwise the block is split to create a hole with an
|
|
/// unconditional branch around it. In either case NewMBB is set to a
|
|
/// block following which the new island can be inserted (the WaterList
|
|
/// is not adjusted).
|
|
void ARMConstantIslands::createNewWater(unsigned CPUserIndex,
|
|
unsigned UserOffset,
|
|
MachineBasicBlock *&NewMBB) {
|
|
CPUser &U = CPUsers[CPUserIndex];
|
|
MachineInstr *UserMI = U.MI;
|
|
MachineInstr *CPEMI = U.CPEMI;
|
|
unsigned CPELogAlign = getCPELogAlign(CPEMI);
|
|
MachineBasicBlock *UserMBB = UserMI->getParent();
|
|
const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
|
|
|
|
// If the block does not end in an unconditional branch already, and if the
|
|
// end of the block is within range, make new water there. (The addition
|
|
// below is for the unconditional branch we will be adding: 4 bytes on ARM +
|
|
// Thumb2, 2 on Thumb1.
|
|
if (BBHasFallthrough(UserMBB)) {
|
|
// Size of branch to insert.
|
|
unsigned Delta = isThumb1 ? 2 : 4;
|
|
// Compute the offset where the CPE will begin.
|
|
unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
|
|
|
|
if (isOffsetInRange(UserOffset, CPEOffset, U)) {
|
|
DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
|
|
<< format(", expected CPE offset %#x\n", CPEOffset));
|
|
NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
|
|
// Add an unconditional branch from UserMBB to fallthrough block. Record
|
|
// it for branch lengthening; this new branch will not get out of range,
|
|
// but if the preceding conditional branch is out of range, the targets
|
|
// will be exchanged, and the altered branch may be out of range, so the
|
|
// machinery has to know about it.
|
|
int UncondBr = isThumb ? ((isThumb2) ? ARM::t2B : ARM::tB) : ARM::B;
|
|
if (!isThumb)
|
|
BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
|
|
else
|
|
BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB)
|
|
.addImm(ARMCC::AL).addReg(0);
|
|
unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
|
|
ImmBranches.push_back(ImmBranch(&UserMBB->back(),
|
|
MaxDisp, false, UncondBr));
|
|
BBInfo[UserMBB->getNumber()].Size += Delta;
|
|
adjustBBOffsetsAfter(UserMBB);
|
|
return;
|
|
}
|
|
}
|
|
|
|
// What a big block. Find a place within the block to split it. This is a
|
|
// little tricky on Thumb1 since instructions are 2 bytes and constant pool
|
|
// entries are 4 bytes: if instruction I references island CPE, and
|
|
// instruction I+1 references CPE', it will not work well to put CPE as far
|
|
// forward as possible, since then CPE' cannot immediately follow it (that
|
|
// location is 2 bytes farther away from I+1 than CPE was from I) and we'd
|
|
// need to create a new island. So, we make a first guess, then walk through
|
|
// the instructions between the one currently being looked at and the
|
|
// possible insertion point, and make sure any other instructions that
|
|
// reference CPEs will be able to use the same island area; if not, we back
|
|
// up the insertion point.
|
|
|
|
// Try to split the block so it's fully aligned. Compute the latest split
|
|
// point where we can add a 4-byte branch instruction, and then align to
|
|
// LogAlign which is the largest possible alignment in the function.
|
|
unsigned LogAlign = MF->getAlignment();
|
|
assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
|
|
unsigned KnownBits = UserBBI.internalKnownBits();
|
|
unsigned UPad = UnknownPadding(LogAlign, KnownBits);
|
|
unsigned BaseInsertOffset = UserOffset + U.getMaxDisp() - UPad;
|
|
DEBUG(dbgs() << format("Split in middle of big block before %#x",
|
|
BaseInsertOffset));
|
|
|
|
// The 4 in the following is for the unconditional branch we'll be inserting
|
|
// (allows for long branch on Thumb1). Alignment of the island is handled
|
|
// inside isOffsetInRange.
|
|
BaseInsertOffset -= 4;
|
|
|
|
DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
|
|
<< " la=" << LogAlign
|
|
<< " kb=" << KnownBits
|
|
<< " up=" << UPad << '\n');
|
|
|
|
// This could point off the end of the block if we've already got constant
|
|
// pool entries following this block; only the last one is in the water list.
|
|
// Back past any possible branches (allow for a conditional and a maximally
|
|
// long unconditional).
|
|
if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
|
|
BaseInsertOffset = UserBBI.postOffset() - UPad - 8;
|
|
DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
|
|
}
|
|
unsigned EndInsertOffset = BaseInsertOffset + 4 + UPad +
|
|
CPEMI->getOperand(2).getImm();
|
|
MachineBasicBlock::iterator MI = UserMI;
|
|
++MI;
|
|
unsigned CPUIndex = CPUserIndex+1;
|
|
unsigned NumCPUsers = CPUsers.size();
|
|
MachineInstr *LastIT = 0;
|
|
for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
|
|
Offset < BaseInsertOffset;
|
|
Offset += TII->GetInstSizeInBytes(MI),
|
|
MI = llvm::next(MI)) {
|
|
assert(MI != UserMBB->end() && "Fell off end of block");
|
|
if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
|
|
CPUser &U = CPUsers[CPUIndex];
|
|
if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
|
|
// Shift intertion point by one unit of alignment so it is within reach.
|
|
BaseInsertOffset -= 1u << LogAlign;
|
|
EndInsertOffset -= 1u << LogAlign;
|
|
}
|
|
// This is overly conservative, as we don't account for CPEMIs being
|
|
// reused within the block, but it doesn't matter much. Also assume CPEs
|
|
// are added in order with alignment padding. We may eventually be able
|
|
// to pack the aligned CPEs better.
|
|
EndInsertOffset += U.CPEMI->getOperand(2).getImm();
|
|
CPUIndex++;
|
|
}
|
|
|
|
// Remember the last IT instruction.
|
|
if (MI->getOpcode() == ARM::t2IT)
|
|
LastIT = MI;
|
|
}
|
|
|
|
--MI;
|
|
|
|
// Avoid splitting an IT block.
|
|
if (LastIT) {
|
|
unsigned PredReg = 0;
|
|
ARMCC::CondCodes CC = getITInstrPredicate(MI, PredReg);
|
|
if (CC != ARMCC::AL)
|
|
MI = LastIT;
|
|
}
|
|
NewMBB = splitBlockBeforeInstr(MI);
|
|
}
|
|
|
|
/// handleConstantPoolUser - Analyze the specified user, checking to see if it
|
|
/// is out-of-range. If so, pick up the constant pool value and move it some
|
|
/// place in-range. Return true if we changed any addresses (thus must run
|
|
/// another pass of branch lengthening), false otherwise.
|
|
bool ARMConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
|
|
CPUser &U = CPUsers[CPUserIndex];
|
|
MachineInstr *UserMI = U.MI;
|
|
MachineInstr *CPEMI = U.CPEMI;
|
|
unsigned CPI = CPEMI->getOperand(1).getIndex();
|
|
unsigned Size = CPEMI->getOperand(2).getImm();
|
|
// Compute this only once, it's expensive.
|
|
unsigned UserOffset = getUserOffset(U);
|
|
|
|
// See if the current entry is within range, or there is a clone of it
|
|
// in range.
|
|
int result = findInRangeCPEntry(U, UserOffset);
|
|
if (result==1) return false;
|
|
else if (result==2) return true;
|
|
|
|
// No existing clone of this CPE is within range.
|
|
// We will be generating a new clone. Get a UID for it.
|
|
unsigned ID = AFI->createPICLabelUId();
|
|
|
|
// Look for water where we can place this CPE.
|
|
MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
|
|
MachineBasicBlock *NewMBB;
|
|
water_iterator IP;
|
|
if (findAvailableWater(U, UserOffset, IP)) {
|
|
DEBUG(dbgs() << "Found water in range\n");
|
|
MachineBasicBlock *WaterBB = *IP;
|
|
|
|
// If the original WaterList entry was "new water" on this iteration,
|
|
// propagate that to the new island. This is just keeping NewWaterList
|
|
// updated to match the WaterList, which will be updated below.
|
|
if (NewWaterList.erase(WaterBB))
|
|
NewWaterList.insert(NewIsland);
|
|
|
|
// The new CPE goes before the following block (NewMBB).
|
|
NewMBB = llvm::next(MachineFunction::iterator(WaterBB));
|
|
|
|
} else {
|
|
// No water found.
|
|
DEBUG(dbgs() << "No water found\n");
|
|
createNewWater(CPUserIndex, UserOffset, NewMBB);
|
|
|
|
// splitBlockBeforeInstr adds to WaterList, which is important when it is
|
|
// called while handling branches so that the water will be seen on the
|
|
// next iteration for constant pools, but in this context, we don't want
|
|
// it. Check for this so it will be removed from the WaterList.
|
|
// Also remove any entry from NewWaterList.
|
|
MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB));
|
|
IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
|
|
if (IP != WaterList.end())
|
|
NewWaterList.erase(WaterBB);
|
|
|
|
// We are adding new water. Update NewWaterList.
|
|
NewWaterList.insert(NewIsland);
|
|
}
|
|
|
|
// Remove the original WaterList entry; we want subsequent insertions in
|
|
// this vicinity to go after the one we're about to insert. This
|
|
// considerably reduces the number of times we have to move the same CPE
|
|
// more than once and is also important to ensure the algorithm terminates.
|
|
if (IP != WaterList.end())
|
|
WaterList.erase(IP);
|
|
|
|
// Okay, we know we can put an island before NewMBB now, do it!
|
|
MF->insert(NewMBB, NewIsland);
|
|
|
|
// Update internal data structures to account for the newly inserted MBB.
|
|
updateForInsertedWaterBlock(NewIsland);
|
|
|
|
// Decrement the old entry, and remove it if refcount becomes 0.
|
|
decrementCPEReferenceCount(CPI, CPEMI);
|
|
|
|
// Now that we have an island to add the CPE to, clone the original CPE and
|
|
// add it to the island.
|
|
U.HighWaterMark = NewIsland;
|
|
U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(ARM::CONSTPOOL_ENTRY))
|
|
.addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
|
|
CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
|
|
++NumCPEs;
|
|
|
|
// Mark the basic block as aligned as required by the const-pool entry.
|
|
NewIsland->setAlignment(getCPELogAlign(U.CPEMI));
|
|
|
|
// Increase the size of the island block to account for the new entry.
|
|
BBInfo[NewIsland->getNumber()].Size += Size;
|
|
adjustBBOffsetsAfter(llvm::prior(MachineFunction::iterator(NewIsland)));
|
|
|
|
// Finally, change the CPI in the instruction operand to be ID.
|
|
for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
|
|
if (UserMI->getOperand(i).isCPI()) {
|
|
UserMI->getOperand(i).setIndex(ID);
|
|
break;
|
|
}
|
|
|
|
DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
|
|
<< format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
|
|
|
|
return true;
|
|
}
|
|
|
|
/// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
|
|
/// sizes and offsets of impacted basic blocks.
|
|
void ARMConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
|
|
MachineBasicBlock *CPEBB = CPEMI->getParent();
|
|
unsigned Size = CPEMI->getOperand(2).getImm();
|
|
CPEMI->eraseFromParent();
|
|
BBInfo[CPEBB->getNumber()].Size -= Size;
|
|
// All succeeding offsets have the current size value added in, fix this.
|
|
if (CPEBB->empty()) {
|
|
BBInfo[CPEBB->getNumber()].Size = 0;
|
|
|
|
// This block no longer needs to be aligned. <rdar://problem/10534709>.
|
|
CPEBB->setAlignment(0);
|
|
} else
|
|
// Entries are sorted by descending alignment, so realign from the front.
|
|
CPEBB->setAlignment(getCPELogAlign(CPEBB->begin()));
|
|
|
|
adjustBBOffsetsAfter(CPEBB);
|
|
// An island has only one predecessor BB and one successor BB. Check if
|
|
// this BB's predecessor jumps directly to this BB's successor. This
|
|
// shouldn't happen currently.
|
|
assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
|
|
// FIXME: remove the empty blocks after all the work is done?
|
|
}
|
|
|
|
/// removeUnusedCPEntries - Remove constant pool entries whose refcounts
|
|
/// are zero.
|
|
bool ARMConstantIslands::removeUnusedCPEntries() {
|
|
unsigned MadeChange = false;
|
|
for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
|
|
std::vector<CPEntry> &CPEs = CPEntries[i];
|
|
for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
|
|
if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
|
|
removeDeadCPEMI(CPEs[j].CPEMI);
|
|
CPEs[j].CPEMI = NULL;
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
}
|
|
return MadeChange;
|
|
}
|
|
|
|
/// isBBInRange - Returns true if the distance between specific MI and
|
|
/// specific BB can fit in MI's displacement field.
|
|
bool ARMConstantIslands::isBBInRange(MachineInstr *MI,MachineBasicBlock *DestBB,
|
|
unsigned MaxDisp) {
|
|
unsigned PCAdj = isThumb ? 4 : 8;
|
|
unsigned BrOffset = getOffsetOf(MI) + PCAdj;
|
|
unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
|
|
|
|
DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
|
|
<< " from BB#" << MI->getParent()->getNumber()
|
|
<< " max delta=" << MaxDisp
|
|
<< " from " << getOffsetOf(MI) << " to " << DestOffset
|
|
<< " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
|
|
|
|
if (BrOffset <= DestOffset) {
|
|
// Branch before the Dest.
|
|
if (DestOffset-BrOffset <= MaxDisp)
|
|
return true;
|
|
} else {
|
|
if (BrOffset-DestOffset <= MaxDisp)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// fixupImmediateBr - Fix up an immediate branch whose destination is too far
|
|
/// away to fit in its displacement field.
|
|
bool ARMConstantIslands::fixupImmediateBr(ImmBranch &Br) {
|
|
MachineInstr *MI = Br.MI;
|
|
MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
|
|
|
|
// Check to see if the DestBB is already in-range.
|
|
if (isBBInRange(MI, DestBB, Br.MaxDisp))
|
|
return false;
|
|
|
|
if (!Br.isCond)
|
|
return fixupUnconditionalBr(Br);
|
|
return fixupConditionalBr(Br);
|
|
}
|
|
|
|
/// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
|
|
/// too far away to fit in its displacement field. If the LR register has been
|
|
/// spilled in the epilogue, then we can use BL to implement a far jump.
|
|
/// Otherwise, add an intermediate branch instruction to a branch.
|
|
bool
|
|
ARMConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
|
|
MachineInstr *MI = Br.MI;
|
|
MachineBasicBlock *MBB = MI->getParent();
|
|
if (!isThumb1)
|
|
llvm_unreachable("fixupUnconditionalBr is Thumb1 only!");
|
|
|
|
// Use BL to implement far jump.
|
|
Br.MaxDisp = (1 << 21) * 2;
|
|
MI->setDesc(TII->get(ARM::tBfar));
|
|
BBInfo[MBB->getNumber()].Size += 2;
|
|
adjustBBOffsetsAfter(MBB);
|
|
HasFarJump = true;
|
|
++NumUBrFixed;
|
|
|
|
DEBUG(dbgs() << " Changed B to long jump " << *MI);
|
|
|
|
return true;
|
|
}
|
|
|
|
/// fixupConditionalBr - Fix up a conditional branch whose destination is too
|
|
/// far away to fit in its displacement field. It is converted to an inverse
|
|
/// conditional branch + an unconditional branch to the destination.
|
|
bool
|
|
ARMConstantIslands::fixupConditionalBr(ImmBranch &Br) {
|
|
MachineInstr *MI = Br.MI;
|
|
MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
|
|
|
|
// Add an unconditional branch to the destination and invert the branch
|
|
// condition to jump over it:
|
|
// blt L1
|
|
// =>
|
|
// bge L2
|
|
// b L1
|
|
// L2:
|
|
ARMCC::CondCodes CC = (ARMCC::CondCodes)MI->getOperand(1).getImm();
|
|
CC = ARMCC::getOppositeCondition(CC);
|
|
unsigned CCReg = MI->getOperand(2).getReg();
|
|
|
|
// If the branch is at the end of its MBB and that has a fall-through block,
|
|
// direct the updated conditional branch to the fall-through block. Otherwise,
|
|
// split the MBB before the next instruction.
|
|
MachineBasicBlock *MBB = MI->getParent();
|
|
MachineInstr *BMI = &MBB->back();
|
|
bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
|
|
|
|
++NumCBrFixed;
|
|
if (BMI != MI) {
|
|
if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) &&
|
|
BMI->getOpcode() == Br.UncondBr) {
|
|
// Last MI in the BB is an unconditional branch. Can we simply invert the
|
|
// condition and swap destinations:
|
|
// beq L1
|
|
// b L2
|
|
// =>
|
|
// bne L2
|
|
// b L1
|
|
MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB();
|
|
if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
|
|
DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
|
|
<< *BMI);
|
|
BMI->getOperand(0).setMBB(DestBB);
|
|
MI->getOperand(0).setMBB(NewDest);
|
|
MI->getOperand(1).setImm(CC);
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (NeedSplit) {
|
|
splitBlockBeforeInstr(MI);
|
|
// No need for the branch to the next block. We're adding an unconditional
|
|
// branch to the destination.
|
|
int delta = TII->GetInstSizeInBytes(&MBB->back());
|
|
BBInfo[MBB->getNumber()].Size -= delta;
|
|
MBB->back().eraseFromParent();
|
|
// BBInfo[SplitBB].Offset is wrong temporarily, fixed below
|
|
}
|
|
MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
|
|
|
|
DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
|
|
<< " also invert condition and change dest. to BB#"
|
|
<< NextBB->getNumber() << "\n");
|
|
|
|
// Insert a new conditional branch and a new unconditional branch.
|
|
// Also update the ImmBranch as well as adding a new entry for the new branch.
|
|
BuildMI(MBB, DebugLoc(), TII->get(MI->getOpcode()))
|
|
.addMBB(NextBB).addImm(CC).addReg(CCReg);
|
|
Br.MI = &MBB->back();
|
|
BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
|
|
if (isThumb)
|
|
BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB)
|
|
.addImm(ARMCC::AL).addReg(0);
|
|
else
|
|
BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
|
|
BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back());
|
|
unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
|
|
ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
|
|
|
|
// Remove the old conditional branch. It may or may not still be in MBB.
|
|
BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI);
|
|
MI->eraseFromParent();
|
|
adjustBBOffsetsAfter(MBB);
|
|
return true;
|
|
}
|
|
|
|
/// undoLRSpillRestore - Remove Thumb push / pop instructions that only spills
|
|
/// LR / restores LR to pc. FIXME: This is done here because it's only possible
|
|
/// to do this if tBfar is not used.
|
|
bool ARMConstantIslands::undoLRSpillRestore() {
|
|
bool MadeChange = false;
|
|
for (unsigned i = 0, e = PushPopMIs.size(); i != e; ++i) {
|
|
MachineInstr *MI = PushPopMIs[i];
|
|
// First two operands are predicates.
|
|
if (MI->getOpcode() == ARM::tPOP_RET &&
|
|
MI->getOperand(2).getReg() == ARM::PC &&
|
|
MI->getNumExplicitOperands() == 3) {
|
|
// Create the new insn and copy the predicate from the old.
|
|
BuildMI(MI->getParent(), MI->getDebugLoc(), TII->get(ARM::tBX_RET))
|
|
.addOperand(MI->getOperand(0))
|
|
.addOperand(MI->getOperand(1));
|
|
MI->eraseFromParent();
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
return MadeChange;
|
|
}
|
|
|
|
// mayOptimizeThumb2Instruction - Returns true if optimizeThumb2Instructions
|
|
// below may shrink MI.
|
|
bool
|
|
ARMConstantIslands::mayOptimizeThumb2Instruction(const MachineInstr *MI) const {
|
|
switch(MI->getOpcode()) {
|
|
// optimizeThumb2Instructions.
|
|
case ARM::t2LEApcrel:
|
|
case ARM::t2LDRpci:
|
|
// optimizeThumb2Branches.
|
|
case ARM::t2B:
|
|
case ARM::t2Bcc:
|
|
case ARM::tBcc:
|
|
// optimizeThumb2JumpTables.
|
|
case ARM::t2BR_JT:
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool ARMConstantIslands::optimizeThumb2Instructions() {
|
|
bool MadeChange = false;
|
|
|
|
// Shrink ADR and LDR from constantpool.
|
|
for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) {
|
|
CPUser &U = CPUsers[i];
|
|
unsigned Opcode = U.MI->getOpcode();
|
|
unsigned NewOpc = 0;
|
|
unsigned Scale = 1;
|
|
unsigned Bits = 0;
|
|
switch (Opcode) {
|
|
default: break;
|
|
case ARM::t2LEApcrel:
|
|
if (isARMLowRegister(U.MI->getOperand(0).getReg())) {
|
|
NewOpc = ARM::tLEApcrel;
|
|
Bits = 8;
|
|
Scale = 4;
|
|
}
|
|
break;
|
|
case ARM::t2LDRpci:
|
|
if (isARMLowRegister(U.MI->getOperand(0).getReg())) {
|
|
NewOpc = ARM::tLDRpci;
|
|
Bits = 8;
|
|
Scale = 4;
|
|
}
|
|
break;
|
|
}
|
|
|
|
if (!NewOpc)
|
|
continue;
|
|
|
|
unsigned UserOffset = getUserOffset(U);
|
|
unsigned MaxOffs = ((1 << Bits) - 1) * Scale;
|
|
|
|
// Be conservative with inline asm.
|
|
if (!U.KnownAlignment)
|
|
MaxOffs -= 2;
|
|
|
|
// FIXME: Check if offset is multiple of scale if scale is not 4.
|
|
if (isCPEntryInRange(U.MI, UserOffset, U.CPEMI, MaxOffs, false, true)) {
|
|
DEBUG(dbgs() << "Shrink: " << *U.MI);
|
|
U.MI->setDesc(TII->get(NewOpc));
|
|
MachineBasicBlock *MBB = U.MI->getParent();
|
|
BBInfo[MBB->getNumber()].Size -= 2;
|
|
adjustBBOffsetsAfter(MBB);
|
|
++NumT2CPShrunk;
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
|
|
MadeChange |= optimizeThumb2Branches();
|
|
MadeChange |= optimizeThumb2JumpTables();
|
|
return MadeChange;
|
|
}
|
|
|
|
bool ARMConstantIslands::optimizeThumb2Branches() {
|
|
bool MadeChange = false;
|
|
|
|
for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) {
|
|
ImmBranch &Br = ImmBranches[i];
|
|
unsigned Opcode = Br.MI->getOpcode();
|
|
unsigned NewOpc = 0;
|
|
unsigned Scale = 1;
|
|
unsigned Bits = 0;
|
|
switch (Opcode) {
|
|
default: break;
|
|
case ARM::t2B:
|
|
NewOpc = ARM::tB;
|
|
Bits = 11;
|
|
Scale = 2;
|
|
break;
|
|
case ARM::t2Bcc: {
|
|
NewOpc = ARM::tBcc;
|
|
Bits = 8;
|
|
Scale = 2;
|
|
break;
|
|
}
|
|
}
|
|
if (NewOpc) {
|
|
unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
|
|
MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB();
|
|
if (isBBInRange(Br.MI, DestBB, MaxOffs)) {
|
|
DEBUG(dbgs() << "Shrink branch: " << *Br.MI);
|
|
Br.MI->setDesc(TII->get(NewOpc));
|
|
MachineBasicBlock *MBB = Br.MI->getParent();
|
|
BBInfo[MBB->getNumber()].Size -= 2;
|
|
adjustBBOffsetsAfter(MBB);
|
|
++NumT2BrShrunk;
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
|
|
Opcode = Br.MI->getOpcode();
|
|
if (Opcode != ARM::tBcc)
|
|
continue;
|
|
|
|
// If the conditional branch doesn't kill CPSR, then CPSR can be liveout
|
|
// so this transformation is not safe.
|
|
if (!Br.MI->killsRegister(ARM::CPSR))
|
|
continue;
|
|
|
|
NewOpc = 0;
|
|
unsigned PredReg = 0;
|
|
ARMCC::CondCodes Pred = getInstrPredicate(Br.MI, PredReg);
|
|
if (Pred == ARMCC::EQ)
|
|
NewOpc = ARM::tCBZ;
|
|
else if (Pred == ARMCC::NE)
|
|
NewOpc = ARM::tCBNZ;
|
|
if (!NewOpc)
|
|
continue;
|
|
MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB();
|
|
// Check if the distance is within 126. Subtract starting offset by 2
|
|
// because the cmp will be eliminated.
|
|
unsigned BrOffset = getOffsetOf(Br.MI) + 4 - 2;
|
|
unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
|
|
if (BrOffset < DestOffset && (DestOffset - BrOffset) <= 126) {
|
|
MachineBasicBlock::iterator CmpMI = Br.MI;
|
|
if (CmpMI != Br.MI->getParent()->begin()) {
|
|
--CmpMI;
|
|
if (CmpMI->getOpcode() == ARM::tCMPi8) {
|
|
unsigned Reg = CmpMI->getOperand(0).getReg();
|
|
Pred = getInstrPredicate(CmpMI, PredReg);
|
|
if (Pred == ARMCC::AL &&
|
|
CmpMI->getOperand(1).getImm() == 0 &&
|
|
isARMLowRegister(Reg)) {
|
|
MachineBasicBlock *MBB = Br.MI->getParent();
|
|
DEBUG(dbgs() << "Fold: " << *CmpMI << " and: " << *Br.MI);
|
|
MachineInstr *NewBR =
|
|
BuildMI(*MBB, CmpMI, Br.MI->getDebugLoc(), TII->get(NewOpc))
|
|
.addReg(Reg).addMBB(DestBB,Br.MI->getOperand(0).getTargetFlags());
|
|
CmpMI->eraseFromParent();
|
|
Br.MI->eraseFromParent();
|
|
Br.MI = NewBR;
|
|
BBInfo[MBB->getNumber()].Size -= 2;
|
|
adjustBBOffsetsAfter(MBB);
|
|
++NumCBZ;
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
/// optimizeThumb2JumpTables - Use tbb / tbh instructions to generate smaller
|
|
/// jumptables when it's possible.
|
|
bool ARMConstantIslands::optimizeThumb2JumpTables() {
|
|
bool MadeChange = false;
|
|
|
|
// FIXME: After the tables are shrunk, can we get rid some of the
|
|
// constantpool tables?
|
|
MachineJumpTableInfo *MJTI = MF->getJumpTableInfo();
|
|
if (MJTI == 0) return false;
|
|
|
|
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
|
|
for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) {
|
|
MachineInstr *MI = T2JumpTables[i];
|
|
const MCInstrDesc &MCID = MI->getDesc();
|
|
unsigned NumOps = MCID.getNumOperands();
|
|
unsigned JTOpIdx = NumOps - (MI->isPredicable() ? 3 : 2);
|
|
MachineOperand JTOP = MI->getOperand(JTOpIdx);
|
|
unsigned JTI = JTOP.getIndex();
|
|
assert(JTI < JT.size());
|
|
|
|
bool ByteOk = true;
|
|
bool HalfWordOk = true;
|
|
unsigned JTOffset = getOffsetOf(MI) + 4;
|
|
const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs;
|
|
for (unsigned j = 0, ee = JTBBs.size(); j != ee; ++j) {
|
|
MachineBasicBlock *MBB = JTBBs[j];
|
|
unsigned DstOffset = BBInfo[MBB->getNumber()].Offset;
|
|
// Negative offset is not ok. FIXME: We should change BB layout to make
|
|
// sure all the branches are forward.
|
|
if (ByteOk && (DstOffset - JTOffset) > ((1<<8)-1)*2)
|
|
ByteOk = false;
|
|
unsigned TBHLimit = ((1<<16)-1)*2;
|
|
if (HalfWordOk && (DstOffset - JTOffset) > TBHLimit)
|
|
HalfWordOk = false;
|
|
if (!ByteOk && !HalfWordOk)
|
|
break;
|
|
}
|
|
|
|
if (ByteOk || HalfWordOk) {
|
|
MachineBasicBlock *MBB = MI->getParent();
|
|
unsigned BaseReg = MI->getOperand(0).getReg();
|
|
bool BaseRegKill = MI->getOperand(0).isKill();
|
|
if (!BaseRegKill)
|
|
continue;
|
|
unsigned IdxReg = MI->getOperand(1).getReg();
|
|
bool IdxRegKill = MI->getOperand(1).isKill();
|
|
|
|
// Scan backwards to find the instruction that defines the base
|
|
// register. Due to post-RA scheduling, we can't count on it
|
|
// immediately preceding the branch instruction.
|
|
MachineBasicBlock::iterator PrevI = MI;
|
|
MachineBasicBlock::iterator B = MBB->begin();
|
|
while (PrevI != B && !PrevI->definesRegister(BaseReg))
|
|
--PrevI;
|
|
|
|
// If for some reason we didn't find it, we can't do anything, so
|
|
// just skip this one.
|
|
if (!PrevI->definesRegister(BaseReg))
|
|
continue;
|
|
|
|
MachineInstr *AddrMI = PrevI;
|
|
bool OptOk = true;
|
|
// Examine the instruction that calculates the jumptable entry address.
|
|
// Make sure it only defines the base register and kills any uses
|
|
// other than the index register.
|
|
for (unsigned k = 0, eee = AddrMI->getNumOperands(); k != eee; ++k) {
|
|
const MachineOperand &MO = AddrMI->getOperand(k);
|
|
if (!MO.isReg() || !MO.getReg())
|
|
continue;
|
|
if (MO.isDef() && MO.getReg() != BaseReg) {
|
|
OptOk = false;
|
|
break;
|
|
}
|
|
if (MO.isUse() && !MO.isKill() && MO.getReg() != IdxReg) {
|
|
OptOk = false;
|
|
break;
|
|
}
|
|
}
|
|
if (!OptOk)
|
|
continue;
|
|
|
|
// Now scan back again to find the tLEApcrel or t2LEApcrelJT instruction
|
|
// that gave us the initial base register definition.
|
|
for (--PrevI; PrevI != B && !PrevI->definesRegister(BaseReg); --PrevI)
|
|
;
|
|
|
|
// The instruction should be a tLEApcrel or t2LEApcrelJT; we want
|
|
// to delete it as well.
|
|
MachineInstr *LeaMI = PrevI;
|
|
if ((LeaMI->getOpcode() != ARM::tLEApcrelJT &&
|
|
LeaMI->getOpcode() != ARM::t2LEApcrelJT) ||
|
|
LeaMI->getOperand(0).getReg() != BaseReg)
|
|
OptOk = false;
|
|
|
|
if (!OptOk)
|
|
continue;
|
|
|
|
DEBUG(dbgs() << "Shrink JT: " << *MI << " addr: " << *AddrMI
|
|
<< " lea: " << *LeaMI);
|
|
unsigned Opc = ByteOk ? ARM::t2TBB_JT : ARM::t2TBH_JT;
|
|
MachineInstr *NewJTMI = BuildMI(MBB, MI->getDebugLoc(), TII->get(Opc))
|
|
.addReg(IdxReg, getKillRegState(IdxRegKill))
|
|
.addJumpTableIndex(JTI, JTOP.getTargetFlags())
|
|
.addImm(MI->getOperand(JTOpIdx+1).getImm());
|
|
DEBUG(dbgs() << "BB#" << MBB->getNumber() << ": " << *NewJTMI);
|
|
// FIXME: Insert an "ALIGN" instruction to ensure the next instruction
|
|
// is 2-byte aligned. For now, asm printer will fix it up.
|
|
unsigned NewSize = TII->GetInstSizeInBytes(NewJTMI);
|
|
unsigned OrigSize = TII->GetInstSizeInBytes(AddrMI);
|
|
OrigSize += TII->GetInstSizeInBytes(LeaMI);
|
|
OrigSize += TII->GetInstSizeInBytes(MI);
|
|
|
|
AddrMI->eraseFromParent();
|
|
LeaMI->eraseFromParent();
|
|
MI->eraseFromParent();
|
|
|
|
int delta = OrigSize - NewSize;
|
|
BBInfo[MBB->getNumber()].Size -= delta;
|
|
adjustBBOffsetsAfter(MBB);
|
|
|
|
++NumTBs;
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
/// reorderThumb2JumpTables - Adjust the function's block layout to ensure that
|
|
/// jump tables always branch forwards, since that's what tbb and tbh need.
|
|
bool ARMConstantIslands::reorderThumb2JumpTables() {
|
|
bool MadeChange = false;
|
|
|
|
MachineJumpTableInfo *MJTI = MF->getJumpTableInfo();
|
|
if (MJTI == 0) return false;
|
|
|
|
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
|
|
for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) {
|
|
MachineInstr *MI = T2JumpTables[i];
|
|
const MCInstrDesc &MCID = MI->getDesc();
|
|
unsigned NumOps = MCID.getNumOperands();
|
|
unsigned JTOpIdx = NumOps - (MI->isPredicable() ? 3 : 2);
|
|
MachineOperand JTOP = MI->getOperand(JTOpIdx);
|
|
unsigned JTI = JTOP.getIndex();
|
|
assert(JTI < JT.size());
|
|
|
|
// We prefer if target blocks for the jump table come after the jump
|
|
// instruction so we can use TB[BH]. Loop through the target blocks
|
|
// and try to adjust them such that that's true.
|
|
int JTNumber = MI->getParent()->getNumber();
|
|
const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs;
|
|
for (unsigned j = 0, ee = JTBBs.size(); j != ee; ++j) {
|
|
MachineBasicBlock *MBB = JTBBs[j];
|
|
int DTNumber = MBB->getNumber();
|
|
|
|
if (DTNumber < JTNumber) {
|
|
// The destination precedes the switch. Try to move the block forward
|
|
// so we have a positive offset.
|
|
MachineBasicBlock *NewBB =
|
|
adjustJTTargetBlockForward(MBB, MI->getParent());
|
|
if (NewBB)
|
|
MJTI->ReplaceMBBInJumpTable(JTI, JTBBs[j], NewBB);
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
MachineBasicBlock *ARMConstantIslands::
|
|
adjustJTTargetBlockForward(MachineBasicBlock *BB, MachineBasicBlock *JTBB) {
|
|
// If the destination block is terminated by an unconditional branch,
|
|
// try to move it; otherwise, create a new block following the jump
|
|
// table that branches back to the actual target. This is a very simple
|
|
// heuristic. FIXME: We can definitely improve it.
|
|
MachineBasicBlock *TBB = 0, *FBB = 0;
|
|
SmallVector<MachineOperand, 4> Cond;
|
|
SmallVector<MachineOperand, 4> CondPrior;
|
|
MachineFunction::iterator BBi = BB;
|
|
MachineFunction::iterator OldPrior = prior(BBi);
|
|
|
|
// If the block terminator isn't analyzable, don't try to move the block
|
|
bool B = TII->AnalyzeBranch(*BB, TBB, FBB, Cond);
|
|
|
|
// If the block ends in an unconditional branch, move it. The prior block
|
|
// has to have an analyzable terminator for us to move this one. Be paranoid
|
|
// and make sure we're not trying to move the entry block of the function.
|
|
if (!B && Cond.empty() && BB != MF->begin() &&
|
|
!TII->AnalyzeBranch(*OldPrior, TBB, FBB, CondPrior)) {
|
|
BB->moveAfter(JTBB);
|
|
OldPrior->updateTerminator();
|
|
BB->updateTerminator();
|
|
// Update numbering to account for the block being moved.
|
|
MF->RenumberBlocks();
|
|
++NumJTMoved;
|
|
return NULL;
|
|
}
|
|
|
|
// Create a new MBB for the code after the jump BB.
|
|
MachineBasicBlock *NewBB =
|
|
MF->CreateMachineBasicBlock(JTBB->getBasicBlock());
|
|
MachineFunction::iterator MBBI = JTBB; ++MBBI;
|
|
MF->insert(MBBI, NewBB);
|
|
|
|
// Add an unconditional branch from NewBB to BB.
|
|
// There doesn't seem to be meaningful DebugInfo available; this doesn't
|
|
// correspond directly to anything in the source.
|
|
assert (isThumb2 && "Adjusting for TB[BH] but not in Thumb2?");
|
|
BuildMI(NewBB, DebugLoc(), TII->get(ARM::t2B)).addMBB(BB)
|
|
.addImm(ARMCC::AL).addReg(0);
|
|
|
|
// Update internal data structures to account for the newly inserted MBB.
|
|
MF->RenumberBlocks(NewBB);
|
|
|
|
// Update the CFG.
|
|
NewBB->addSuccessor(BB);
|
|
JTBB->removeSuccessor(BB);
|
|
JTBB->addSuccessor(NewBB);
|
|
|
|
++NumJTInserted;
|
|
return NewBB;
|
|
}
|