diff options
Diffstat (limited to 'lib/CodeGen/PeepholeOptimizer.cpp')
-rw-r--r-- | lib/CodeGen/PeepholeOptimizer.cpp | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp index 91c33c4af4..d9474bf240 100644 --- a/lib/CodeGen/PeepholeOptimizer.cpp +++ b/lib/CodeGen/PeepholeOptimizer.cpp @@ -78,6 +78,7 @@ 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 folded"); +STATISTIC(NumLoadFold, "Number of loads folded"); namespace { class PeepholeOptimizer : public MachineFunctionPass { @@ -114,6 +115,7 @@ namespace { bool foldImmediate(MachineInstr *MI, MachineBasicBlock *MBB, SmallSet<unsigned, 4> &ImmDefRegs, DenseMap<unsigned, MachineInstr*> &ImmDefMIs); + bool isLoadFoldable(MachineInstr *MI, unsigned &FoldAsLoadDefReg); }; } @@ -384,6 +386,29 @@ bool PeepholeOptimizer::optimizeCmpInstr(MachineInstr *MI, return false; } +/// 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()) { + const MCInstrDesc &MCID = MI->getDesc(); + if (MCID.getNumDefs() == 1) { + unsigned Reg = MI->getOperand(0).getReg(); + // To reduce compilation time, we check MRI->hasOneUse 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->hasOneUse(Reg)) { + FoldAsLoadDefReg = Reg; + return true; + } + } + } + return false; +} + bool PeepholeOptimizer::isMoveImmediate(MachineInstr *MI, SmallSet<unsigned, 4> &ImmDefRegs, DenseMap<unsigned, MachineInstr*> &ImmDefMIs) { @@ -441,6 +466,7 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { 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; @@ -448,6 +474,7 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { LocalMIs.clear(); ImmDefRegs.clear(); ImmDefMIs.clear(); + FoldAsLoadDefReg = 0; bool First = true; MachineBasicBlock::iterator PMII; @@ -456,12 +483,17 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { MachineInstr *MI = &*MII; LocalMIs.insert(MI); + // If there exists an instruction which belongs to the following + // categories, we will discard the load candidate. if (MI->isLabel() || MI->isPHI() || MI->isImplicitDef() || MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() || MI->hasUnmodeledSideEffects()) { + FoldAsLoadDefReg = 0; ++MII; continue; } + if (MI->mayStore() || MI->isCall()) + FoldAsLoadDefReg = 0; if (MI->isBitcast()) { if (optimizeBitcastInstr(MI, MBB)) { @@ -489,6 +521,31 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) { Changed |= foldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs); } + // 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. + MachineInstr *DefMI = 0; + MachineInstr *FoldMI = TII->optimizeLoadInstr(MI, MRI, + FoldAsLoadDefReg, DefMI); + if (FoldMI) { + // Update LocalMIs since we replaced MI with FoldMI and deleted DefMI. + LocalMIs.erase(MI); + LocalMIs.erase(DefMI); + LocalMIs.insert(FoldMI); + MI->eraseFromParent(); + DefMI->eraseFromParent(); + ++NumLoadFold; + + // MI is replaced with FoldMI. + Changed = true; + PMII = FoldMI; + MII = llvm::next(PMII); + continue; + } + } First = false; PMII = MII; ++MII; |