// same flag that the "cmp" instruction sets and that "bz" uses, then we can
// eliminate the "cmp" instruction.
//
-// - Optimize Bitcast pairs:
+// Another instance, in this code:
//
-// v1 = bitcast v0
-// v2 = bitcast v1
-// = v2
+// sub r1, r3 | sub r1, imm
+// cmp r3, r1 or cmp r1, r3 | cmp r1, imm
+// bge L1
+//
+// If the branch instruction can use flag from "sub", then we can replace
+// "sub" with "subs" and eliminate the "cmp" instruction.
+//
+// - Optimize Loads:
+//
+// Loads that can be folded into a later instruction. A load is foldable
+// if it loads to virtual registers and the virtual register defined has
+// a single use.
+//
+// - Optimize Copies and Bitcast:
+//
+// Rewrite copies and bitcasts to avoid cross register bank copies
+// when possible.
+// E.g., Consider the following example, where capital and lower
+// letters denote different register file:
+// b = copy A <-- cross-bank copy
+// C = copy b <-- cross-bank copy
// =>
-// v1 = bitcast v0
-// = v0
+// b = copy A <-- cross-bank copy
+// C = copy A <-- same-bank copy
//
+// E.g., for bitcast:
+// b = bitcast A <-- cross-bank copy
+// C = bitcast b <-- cross-bank copy
+// =>
+// b = bitcast A <-- cross-bank copy
+// C = copy A <-- same-bank copy
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "peephole-opt"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallSet.h"
-#include "llvm/ADT/Statistic.h"
using namespace llvm;
// Optimize Extensions
cl::desc("Disable the peephole optimizer"));
STATISTIC(NumReuse, "Number of extension results reused");
-STATISTIC(NumBitcasts, "Number of bitcasts eliminated");
STATISTIC(NumCmps, "Number of compares eliminated");
-STATISTIC(NumImmFold, "Number of move immediate foled");
+STATISTIC(NumImmFold, "Number of move immediate folded");
+STATISTIC(NumLoadFold, "Number of loads folded");
+STATISTIC(NumSelects, "Number of selects optimized");
+STATISTIC(NumCopiesBitcasts, "Number of copies/bitcasts optimized");
namespace {
class PeepholeOptimizer : public MachineFunctionPass {
initializePeepholeOptimizerPass(*PassRegistry::getPassRegistry());
}
- virtual bool runOnMachineFunction(MachineFunction &MF);
+ bool runOnMachineFunction(MachineFunction &MF) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
if (Aggressive) {
}
private:
- bool OptimizeBitcastInstr(MachineInstr *MI, MachineBasicBlock *MBB);
- bool OptimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
- bool OptimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
+ bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
+ bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs);
+ bool optimizeSelect(MachineInstr *MI);
+ bool optimizeCopyOrBitcast(MachineInstr *MI);
bool isMoveImmediate(MachineInstr *MI,
SmallSet<unsigned, 4> &ImmDefRegs,
DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
- bool FoldImmediate(MachineInstr *MI, MachineBasicBlock *MBB,
+ bool foldImmediate(MachineInstr *MI, MachineBasicBlock *MBB,
SmallSet<unsigned, 4> &ImmDefRegs,
DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
+ bool isLoadFoldable(MachineInstr *MI, unsigned &FoldAsLoadDefReg);
};
}
INITIALIZE_PASS_END(PeepholeOptimizer, "peephole-opts",
"Peephole Optimizations", false, false)
-/// OptimizeExtInstr - If instruction is a copy-like instruction, i.e. it reads
+/// optimizeExtInstr - If instruction is a copy-like instruction, i.e. it reads
/// a single register and writes a single register and it does not modify the
/// source, and if the source value is preserved as a sub-register of the
/// result, then replace all reachable uses of the source with the subreg of the
/// the code. Since this code does not currently share EXTRACTs, just ignore all
/// debug uses.
bool PeepholeOptimizer::
-OptimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
+optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs) {
unsigned SrcReg, DstReg, SubIdx;
if (!TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx))
TargetRegisterInfo::isPhysicalRegister(SrcReg))
return false;
- MachineRegisterInfo::use_nodbg_iterator UI = MRI->use_nodbg_begin(SrcReg);
- if (++UI == MRI->use_nodbg_end())
+ if (MRI->hasOneNonDBGUse(SrcReg))
// No other uses.
return false;
+ // Ensure DstReg can get a register class that actually supports
+ // sub-registers. Don't change the class until we commit.
+ const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg);
+ DstRC = TM->getRegisterInfo()->getSubClassWithSubReg(DstRC, SubIdx);
+ if (!DstRC)
+ return false;
+
+ // The ext instr may be operating on a sub-register of SrcReg as well.
+ // PPC::EXTSW is a 32 -> 64-bit sign extension, but it reads a 64-bit
+ // register.
+ // If UseSrcSubIdx is Set, SubIdx also applies to SrcReg, and only uses of
+ // SrcReg:SubIdx should be replaced.
+ bool UseSrcSubIdx = TM->getRegisterInfo()->
+ getSubClassWithSubReg(MRI->getRegClass(SrcReg), SubIdx) != 0;
+
// The source has other uses. See if we can replace the other uses with use of
// the result of the extension.
SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs;
- UI = MRI->use_nodbg_begin(DstReg);
- for (MachineRegisterInfo::use_nodbg_iterator UE = MRI->use_nodbg_end();
+ for (MachineRegisterInfo::use_nodbg_iterator
+ UI = MRI->use_nodbg_begin(DstReg), UE = MRI->use_nodbg_end();
UI != UE; ++UI)
ReachedBBs.insert(UI->getParent());
SmallVector<MachineOperand*, 8> ExtendedUses;
bool ExtendLife = true;
- UI = MRI->use_nodbg_begin(SrcReg);
- for (MachineRegisterInfo::use_nodbg_iterator UE = MRI->use_nodbg_end();
+ for (MachineRegisterInfo::use_nodbg_iterator
+ UI = MRI->use_nodbg_begin(SrcReg), UE = MRI->use_nodbg_end();
UI != UE; ++UI) {
MachineOperand &UseMO = UI.getOperand();
MachineInstr *UseMI = &*UI;
continue;
}
+ // Only accept uses of SrcReg:SubIdx.
+ if (UseSrcSubIdx && UseMO.getSubReg() != SubIdx)
+ continue;
+
// It's an error to translate this:
//
// %reg1025 = <sext> %reg1024
// Look for PHI uses of the extended result, we don't want to extend the
// liveness of a PHI input. It breaks all kinds of assumptions down
// stream. A PHI use is expected to be the kill of its source values.
- UI = MRI->use_nodbg_begin(DstReg);
for (MachineRegisterInfo::use_nodbg_iterator
- UE = MRI->use_nodbg_end(); UI != UE; ++UI)
+ UI = MRI->use_nodbg_begin(DstReg), UE = MRI->use_nodbg_end();
+ UI != UE; ++UI)
if (UI->isPHI())
PHIBBs.insert(UI->getParent());
if (PHIBBs.count(UseMBB))
continue;
+ // About to add uses of DstReg, clear DstReg's kill flags.
+ if (!Changed) {
+ MRI->clearKillFlags(DstReg);
+ MRI->constrainRegClass(DstReg, DstRC);
+ }
+
unsigned NewVR = MRI->createVirtualRegister(RC);
- BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
- TII->get(TargetOpcode::COPY), NewVR)
+ MachineInstr *Copy = BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
+ TII->get(TargetOpcode::COPY), NewVR)
.addReg(DstReg, 0, SubIdx);
-
+ // SubIdx applies to both SrcReg and DstReg when UseSrcSubIdx is set.
+ if (UseSrcSubIdx) {
+ Copy->getOperand(0).setSubReg(SubIdx);
+ Copy->getOperand(0).setIsUndef();
+ }
UseMO->setReg(NewVR);
++NumReuse;
Changed = true;
return Changed;
}
-/// OptimizeBitcastInstr - If the instruction is a bitcast instruction A that
-/// cannot be optimized away during isel (e.g. ARM::VMOVSR, which bitcast
-/// a value cross register classes), and the source is defined by another
-/// bitcast instruction B. And if the register class of source of B matches
-/// the register class of instruction A, then it is legal to replace all uses
-/// of the def of A with source of B. e.g.
-/// %vreg0<def> = VMOVSR %vreg1
-/// %vreg3<def> = VMOVRS %vreg0
-/// Replace all uses of vreg3 with vreg1.
-
-bool PeepholeOptimizer::OptimizeBitcastInstr(MachineInstr *MI,
- MachineBasicBlock *MBB) {
- unsigned NumDefs = MI->getDesc().getNumDefs();
- unsigned NumSrcs = MI->getDesc().getNumOperands() - NumDefs;
- if (NumDefs != 1)
+/// optimizeCmpInstr - If the instruction is a compare and the previous
+/// instruction it's comparing against all ready sets (or could be modified to
+/// set) the same flag as the compare, then we can remove the comparison and use
+/// the flag from the previous instruction.
+bool PeepholeOptimizer::optimizeCmpInstr(MachineInstr *MI,
+ MachineBasicBlock *MBB) {
+ // If this instruction is a comparison against zero and isn't comparing a
+ // physical register, we can try to optimize it.
+ unsigned SrcReg, SrcReg2;
+ int CmpMask, CmpValue;
+ if (!TII->analyzeCompare(MI, SrcReg, SrcReg2, CmpMask, CmpValue) ||
+ TargetRegisterInfo::isPhysicalRegister(SrcReg) ||
+ (SrcReg2 != 0 && TargetRegisterInfo::isPhysicalRegister(SrcReg2)))
return false;
- unsigned Def = 0;
- unsigned Src = 0;
- for (unsigned i = 0, e = NumDefs + NumSrcs; i != e; ++i) {
- const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg())
- continue;
- unsigned Reg = MO.getReg();
- if (!Reg)
+ // Attempt to optimize the comparison instruction.
+ if (TII->optimizeCompareInstr(MI, SrcReg, SrcReg2, CmpMask, CmpValue, MRI)) {
+ ++NumCmps;
+ return true;
+ }
+
+ return false;
+}
+
+/// Optimize a select instruction.
+bool PeepholeOptimizer::optimizeSelect(MachineInstr *MI) {
+ unsigned TrueOp = 0;
+ unsigned FalseOp = 0;
+ bool Optimizable = false;
+ SmallVector<MachineOperand, 4> Cond;
+ if (TII->analyzeSelect(MI, Cond, TrueOp, FalseOp, Optimizable))
+ return false;
+ if (!Optimizable)
+ return false;
+ if (!TII->optimizeSelect(MI))
+ return false;
+ MI->eraseFromParent();
+ ++NumSelects;
+ return true;
+}
+
+/// \brief Check if the registers defined by the pair (RegisterClass, SubReg)
+/// share the same register file.
+static bool shareSameRegisterFile(const TargetRegisterInfo &TRI,
+ const TargetRegisterClass *DefRC,
+ unsigned DefSubReg,
+ const TargetRegisterClass *SrcRC,
+ unsigned SrcSubReg) {
+ // Same register class.
+ if (DefRC == SrcRC)
+ return true;
+
+ // Both operands are sub registers. Check if they share a register class.
+ unsigned SrcIdx, DefIdx;
+ if (SrcSubReg && DefSubReg)
+ return TRI.getCommonSuperRegClass(SrcRC, SrcSubReg, DefRC, DefSubReg,
+ SrcIdx, DefIdx) != NULL;
+ // At most one of the register is a sub register, make it Src to avoid
+ // duplicating the test.
+ if (!SrcSubReg) {
+ std::swap(DefSubReg, SrcSubReg);
+ std::swap(DefRC, SrcRC);
+ }
+
+ // One of the register is a sub register, check if we can get a superclass.
+ if (SrcSubReg)
+ return TRI.getMatchingSuperRegClass(SrcRC, DefRC, SrcSubReg) != NULL;
+ // Plain copy.
+ return TRI.getCommonSubClass(DefRC, SrcRC) != NULL;
+}
+
+/// \brief Get the index of the definition and source for \p Copy
+/// instruction.
+/// \pre Copy.isCopy() or Copy.isBitcast().
+/// \return True if the Copy instruction has only one register source
+/// and one register definition. Otherwise, \p DefIdx and \p SrcIdx
+/// are invalid.
+static bool getCopyOrBitcastDefUseIdx(const MachineInstr &Copy,
+ unsigned &DefIdx, unsigned &SrcIdx) {
+ assert((Copy.isCopy() || Copy.isBitcast()) && "Wrong operation type.");
+ if (Copy.isCopy()) {
+ // Copy instruction are supposed to be: Def = Src.
+ if (Copy.getDesc().getNumOperands() != 2)
+ return false;
+ DefIdx = 0;
+ SrcIdx = 1;
+ assert(Copy.getOperand(DefIdx).isDef() && "Use comes before def!");
+ return true;
+ }
+ // Bitcast case.
+ // Bitcasts with more than one def are not supported.
+ if (Copy.getDesc().getNumDefs() != 1)
+ return false;
+ // Initialize SrcIdx to an undefined operand.
+ SrcIdx = Copy.getDesc().getNumOperands();
+ for (unsigned OpIdx = 0, EndOpIdx = SrcIdx; OpIdx != EndOpIdx; ++OpIdx) {
+ const MachineOperand &MO = Copy.getOperand(OpIdx);
+ if (!MO.isReg() || !MO.getReg())
continue;
if (MO.isDef())
- Def = Reg;
- else if (Src)
+ DefIdx = OpIdx;
+ else if (SrcIdx != EndOpIdx)
// Multiple sources?
return false;
- else
- Src = Reg;
+ SrcIdx = OpIdx;
}
+ return true;
+}
- assert(Def && Src && "Malformed bitcast instruction!");
-
- MachineInstr *DefMI = MRI->getVRegDef(Src);
- if (!DefMI || !DefMI->isBitcast())
+/// \brief Optimize a copy or bitcast instruction to avoid cross
+/// register bank copy. The optimization looks through a chain of
+/// copies and try to find a source that has a compatible register
+/// class.
+/// Two register classes are considered to be compatible if they share
+/// the same register bank.
+/// New copies issued by this optimization are register allocator
+/// friendly. This optimization does not remove any copy as it may
+/// overconstraint the register allocator, but replaces some when
+/// possible.
+/// \pre \p MI is a Copy (MI->isCopy() is true)
+/// \return True, when \p MI has been optimized. In that case, \p MI has
+/// been removed from its parent.
+bool PeepholeOptimizer::optimizeCopyOrBitcast(MachineInstr *MI) {
+ unsigned DefIdx, SrcIdx;
+ if (!MI || !getCopyOrBitcastDefUseIdx(*MI, DefIdx, SrcIdx))
return false;
- unsigned SrcSrc = 0;
- NumDefs = DefMI->getDesc().getNumDefs();
- NumSrcs = DefMI->getDesc().getNumOperands() - NumDefs;
- if (NumDefs != 1)
+ const MachineOperand &MODef = MI->getOperand(DefIdx);
+ assert(MODef.isReg() && "Copies must be between registers.");
+ unsigned Def = MODef.getReg();
+
+ if (TargetRegisterInfo::isPhysicalRegister(Def))
return false;
- for (unsigned i = 0, e = NumDefs + NumSrcs; i != e; ++i) {
- const MachineOperand &MO = DefMI->getOperand(i);
- if (!MO.isReg() || MO.isDef())
- continue;
- unsigned Reg = MO.getReg();
- if (!Reg)
- continue;
- if (!MO.isDef()) {
- if (SrcSrc)
- // Multiple sources?
- return false;
- else
- SrcSrc = Reg;
- }
- }
- if (MRI->getRegClass(SrcSrc) != MRI->getRegClass(Def))
+ const TargetRegisterClass *DefRC = MRI->getRegClass(Def);
+ unsigned DefSubReg = MODef.getSubReg();
+
+ unsigned Src;
+ unsigned SrcSubReg;
+ bool ShouldRewrite = false;
+ MachineInstr *Copy = MI;
+ const TargetRegisterInfo &TRI = *TM->getRegisterInfo();
+
+ // Follow the chain of copies until we reach the top or find a
+ // more suitable source.
+ do {
+ unsigned CopyDefIdx, CopySrcIdx;
+ if (!getCopyOrBitcastDefUseIdx(*Copy, CopyDefIdx, CopySrcIdx))
+ break;
+ const MachineOperand &MO = Copy->getOperand(CopySrcIdx);
+ assert(MO.isReg() && "Copies must be between registers.");
+ Src = MO.getReg();
+
+ if (TargetRegisterInfo::isPhysicalRegister(Src))
+ break;
+
+ const TargetRegisterClass *SrcRC = MRI->getRegClass(Src);
+ SrcSubReg = MO.getSubReg();
+
+ // If this source does not incur a cross register bank copy, use it.
+ ShouldRewrite = shareSameRegisterFile(TRI, DefRC, DefSubReg, SrcRC,
+ SrcSubReg);
+ // Follow the chain of copies: get the definition of Src.
+ Copy = MRI->getVRegDef(Src);
+ } while (!ShouldRewrite && Copy && (Copy->isCopy() || Copy->isBitcast()));
+
+ // If we did not find a more suitable source, there is nothing to optimize.
+ if (!ShouldRewrite || Src == MI->getOperand(SrcIdx).getReg())
return false;
- MRI->replaceRegWith(Def, SrcSrc);
- MRI->clearKillFlags(SrcSrc);
+ // Rewrite the copy to avoid a cross register bank penalty.
+ unsigned NewVR = TargetRegisterInfo::isPhysicalRegister(Def) ? Def :
+ MRI->createVirtualRegister(DefRC);
+ MachineInstr *NewCopy = BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
+ TII->get(TargetOpcode::COPY), NewVR)
+ .addReg(Src, 0, SrcSubReg);
+ NewCopy->getOperand(0).setSubReg(DefSubReg);
+
+ MRI->replaceRegWith(Def, NewVR);
+ MRI->clearKillFlags(NewVR);
MI->eraseFromParent();
- ++NumBitcasts;
+ ++NumCopiesBitcasts;
return true;
}
-/// OptimizeCmpInstr - If the instruction is a compare and the previous
-/// instruction it's comparing against all ready sets (or could be modified to
-/// set) the same flag as the compare, then we can remove the comparison and use
-/// the flag from the previous instruction.
-bool PeepholeOptimizer::OptimizeCmpInstr(MachineInstr *MI,
- MachineBasicBlock *MBB) {
- // If this instruction is a comparison against zero and isn't comparing a
- // physical register, we can try to optimize it.
- unsigned SrcReg;
- int CmpMask, CmpValue;
- if (!TII->AnalyzeCompare(MI, SrcReg, CmpMask, CmpValue) ||
- TargetRegisterInfo::isPhysicalRegister(SrcReg))
+/// isLoadFoldable - Check whether MI is a candidate for folding into a later
+/// instruction. We only fold loads to virtual registers and the virtual
+/// register defined has a single use.
+bool PeepholeOptimizer::isLoadFoldable(MachineInstr *MI,
+ unsigned &FoldAsLoadDefReg) {
+ if (!MI->canFoldAsLoad() || !MI->mayLoad())
+ return false;
+ const MCInstrDesc &MCID = MI->getDesc();
+ if (MCID.getNumDefs() != 1)
return false;
- // Attempt to optimize the comparison instruction.
- if (TII->OptimizeCompareInstr(MI, SrcReg, CmpMask, CmpValue, MRI)) {
- ++NumCmps;
+ unsigned Reg = MI->getOperand(0).getReg();
+ // To reduce compilation time, we check MRI->hasOneNonDBGUse when inserting
+ // loads. It should be checked when processing uses of the load, since
+ // uses can be removed during peephole.
+ if (!MI->getOperand(0).getSubReg() &&
+ TargetRegisterInfo::isVirtualRegister(Reg) &&
+ MRI->hasOneNonDBGUse(Reg)) {
+ FoldAsLoadDefReg = Reg;
return true;
}
-
return false;
}
return false;
}
-/// FoldImmediate - Try folding register operands that are defined by move
+/// foldImmediate - Try folding register operands that are defined by move
/// immediate instructions, i.e. a trivial constant folding optimization, if
/// and only if the def and use are in the same BB.
-bool PeepholeOptimizer::FoldImmediate(MachineInstr *MI, MachineBasicBlock *MBB,
+bool PeepholeOptimizer::foldImmediate(MachineInstr *MI, MachineBasicBlock *MBB,
SmallSet<unsigned, 4> &ImmDefRegs,
DenseMap<unsigned, MachineInstr*> &ImmDefMIs) {
for (unsigned i = 0, e = MI->getDesc().getNumOperands(); i != e; ++i) {
}
bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
+ DEBUG(dbgs() << "********** PEEPHOLE OPTIMIZER **********\n");
+ DEBUG(dbgs() << "********** Function: " << MF.getName() << '\n');
+
if (DisablePeephole)
return false;
SmallPtrSet<MachineInstr*, 8> LocalMIs;
SmallSet<unsigned, 4> ImmDefRegs;
DenseMap<unsigned, MachineInstr*> ImmDefMIs;
+ unsigned FoldAsLoadDefReg;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock *MBB = &*I;
LocalMIs.clear();
ImmDefRegs.clear();
ImmDefMIs.clear();
+ FoldAsLoadDefReg = 0;
- bool First = true;
- MachineBasicBlock::iterator PMII;
for (MachineBasicBlock::iterator
MII = I->begin(), MIE = I->end(); MII != MIE; ) {
MachineInstr *MI = &*MII;
+ // We may be erasing MI below, increment MII now.
+ ++MII;
LocalMIs.insert(MI);
- if (MI->isLabel() || MI->isPHI() || MI->isImplicitDef() ||
- MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
+ // Skip debug values. They should not affect this peephole optimization.
+ if (MI->isDebugValue())
+ continue;
+
+ // If there exists an instruction which belongs to the following
+ // categories, we will discard the load candidate.
+ if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() ||
+ MI->isKill() || MI->isInlineAsm() ||
MI->hasUnmodeledSideEffects()) {
- ++MII;
+ FoldAsLoadDefReg = 0;
continue;
}
-
- if (MI->isBitcast()) {
- if (OptimizeBitcastInstr(MI, MBB)) {
- // MI is deleted.
- LocalMIs.erase(MI);
- Changed = true;
- MII = First ? I->begin() : llvm::next(PMII);
- continue;
- }
- } else if (MI->isCompare()) {
- if (OptimizeCmpInstr(MI, MBB)) {
- // MI is deleted.
- LocalMIs.erase(MI);
- Changed = true;
- MII = First ? I->begin() : llvm::next(PMII);
- continue;
- }
+ if (MI->mayStore() || MI->isCall())
+ FoldAsLoadDefReg = 0;
+
+ if (((MI->isBitcast() || MI->isCopy()) && optimizeCopyOrBitcast(MI)) ||
+ (MI->isCompare() && optimizeCmpInstr(MI, MBB)) ||
+ (MI->isSelect() && optimizeSelect(MI))) {
+ // MI is deleted.
+ LocalMIs.erase(MI);
+ Changed = true;
+ continue;
}
if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
SeenMoveImm = true;
} else {
- Changed |= OptimizeExtInstr(MI, MBB, LocalMIs);
+ Changed |= optimizeExtInstr(MI, MBB, LocalMIs);
+ // optimizeExtInstr might have created new instructions after MI
+ // and before the already incremented MII. Adjust MII so that the
+ // next iteration sees the new instructions.
+ MII = MI;
+ ++MII;
if (SeenMoveImm)
- Changed |= FoldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
+ Changed |= foldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
}
- First = false;
- PMII = MII;
- ++MII;
+ // Check whether MI is a load candidate for folding into a later
+ // instruction. If MI is not a candidate, check whether we can fold an
+ // earlier load into MI.
+ if (!isLoadFoldable(MI, FoldAsLoadDefReg) && FoldAsLoadDefReg) {
+ // We need to fold load after optimizeCmpInstr, since optimizeCmpInstr
+ // can enable folding by converting SUB to CMP.
+ // Save FoldAsLoadDefReg because optimizeLoadInstr() resets it and we
+ // need it for markUsesInDebugValueAsUndef().
+ unsigned FoldedReg = FoldAsLoadDefReg;
+ MachineInstr *DefMI = 0;
+ MachineInstr *FoldMI = TII->optimizeLoadInstr(MI, MRI,
+ FoldAsLoadDefReg, DefMI);
+ if (FoldMI) {
+ // Update LocalMIs since we replaced MI with FoldMI and deleted DefMI.
+ DEBUG(dbgs() << "Replacing: " << *MI);
+ DEBUG(dbgs() << " With: " << *FoldMI);
+ LocalMIs.erase(MI);
+ LocalMIs.erase(DefMI);
+ LocalMIs.insert(FoldMI);
+ MI->eraseFromParent();
+ DefMI->eraseFromParent();
+ MRI->markUsesInDebugValueAsUndef(FoldedReg);
+ ++NumLoadFold;
+
+ // MI is replaced with FoldMI.
+ Changed = true;
+ continue;
+ }
+ }
}
}
projects / oota-llvm.git / blobdiff