// If the "sub" instruction all ready sets (or could be modified to set) the
// same flag that the "cmp" instruction sets and that "bz" uses, then we can
// eliminate the "cmp" instruction.
+//
+// - Optimize Bitcast pairs:
+//
+// v1 = bitcast v0
+// v2 = bitcast v1
+// = v2
+// =>
+// v1 = bitcast v0
+// = v0
//
//===----------------------------------------------------------------------===//
#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;
Aggressive("aggressive-ext-opt", cl::Hidden,
cl::desc("Aggressive extension optimization"));
+static cl::opt<bool>
+DisablePeephole("disable-peephole", cl::Hidden, cl::init(false),
+ cl::desc("Disable the peephole optimizer"));
+
STATISTIC(NumReuse, "Number of extension results reused");
-STATISTIC(NumEliminated, "Number of compares eliminated");
+STATISTIC(NumBitcasts, "Number of bitcasts eliminated");
+STATISTIC(NumCmps, "Number of compares eliminated");
+STATISTIC(NumImmFold, "Number of move immediate foled");
namespace {
class PeepholeOptimizer : public MachineFunctionPass {
}
private:
- bool OptimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB,
- MachineBasicBlock::iterator &MII);
+ bool OptimizeBitcastInstr(MachineInstr *MI, MachineBasicBlock *MBB);
+ bool OptimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
bool OptimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs);
+ bool isMoveImmediate(MachineInstr *MI,
+ SmallSet<unsigned, 4> &ImmDefRegs,
+ DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
+ bool FoldImmediate(MachineInstr *MI, MachineBasicBlock *MBB,
+ SmallSet<unsigned, 4> &ImmDefRegs,
+ DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
};
}
bool PeepholeOptimizer::
OptimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSet<MachineInstr*, 8> &LocalMIs) {
- LocalMIs.insert(MI);
-
unsigned SrcReg, DstReg, SubIdx;
if (!TII->isCoalescableExtInstr(*MI, SrcReg, DstReg, SubIdx))
return false;
-
+
if (TargetRegisterInfo::isPhysicalRegister(DstReg) ||
TargetRegisterInfo::isPhysicalRegister(SrcReg))
return false;
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)
+ 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)
+ continue;
+ if (MO.isDef())
+ Def = Reg;
+ else if (Src)
+ // Multiple sources?
+ return false;
+ else
+ Src = Reg;
+ }
+
+ assert(Def && Src && "Malformed bitcast instruction!");
+
+ MachineInstr *DefMI = MRI->getVRegDef(Src);
+ if (!DefMI || !DefMI->getDesc().isBitcast())
+ return false;
+
+ unsigned SrcSrc = 0;
+ NumDefs = DefMI->getDesc().getNumDefs();
+ NumSrcs = DefMI->getDesc().getNumOperands() - NumDefs;
+ if (NumDefs != 1)
+ 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))
+ return false;
+
+ MRI->replaceRegWith(Def, SrcSrc);
+ MRI->clearKillFlags(SrcSrc);
+ MI->eraseFromParent();
+ ++NumBitcasts;
+ 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,
- MachineBasicBlock::iterator &NextIter){
+ 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;
return false;
// Attempt to optimize the comparison instruction.
- if (TII->OptimizeCompareInstr(MI, SrcReg, CmpMask, CmpValue, MRI, NextIter)) {
- ++NumEliminated;
+ if (TII->OptimizeCompareInstr(MI, SrcReg, CmpMask, CmpValue, MRI)) {
+ ++NumCmps;
return true;
}
return false;
}
+bool PeepholeOptimizer::isMoveImmediate(MachineInstr *MI,
+ SmallSet<unsigned, 4> &ImmDefRegs,
+ DenseMap<unsigned, MachineInstr*> &ImmDefMIs) {
+ const MCInstrDesc &MCID = MI->getDesc();
+ if (!MCID.isMoveImmediate())
+ return false;
+ if (MCID.getNumDefs() != 1)
+ return false;
+ unsigned Reg = MI->getOperand(0).getReg();
+ if (TargetRegisterInfo::isVirtualRegister(Reg)) {
+ ImmDefMIs.insert(std::make_pair(Reg, MI));
+ ImmDefRegs.insert(Reg);
+ return true;
+ }
+
+ return false;
+}
+
+/// 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,
+ SmallSet<unsigned, 4> &ImmDefRegs,
+ DenseMap<unsigned, MachineInstr*> &ImmDefMIs) {
+ for (unsigned i = 0, e = MI->getDesc().getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || MO.isDef())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(Reg))
+ continue;
+ if (ImmDefRegs.count(Reg) == 0)
+ continue;
+ DenseMap<unsigned, MachineInstr*>::iterator II = ImmDefMIs.find(Reg);
+ assert(II != ImmDefMIs.end());
+ if (TII->FoldImmediate(MI, II->second, Reg, MRI)) {
+ ++NumImmFold;
+ return true;
+ }
+ }
+ return false;
+}
+
bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
+ if (DisablePeephole)
+ return false;
+
TM = &MF.getTarget();
TII = TM->getInstrInfo();
MRI = &MF.getRegInfo();
bool Changed = false;
SmallPtrSet<MachineInstr*, 8> LocalMIs;
+ SmallSet<unsigned, 4> ImmDefRegs;
+ DenseMap<unsigned, MachineInstr*> ImmDefMIs;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock *MBB = &*I;
+
+ bool SeenMoveImm = false;
LocalMIs.clear();
+ ImmDefRegs.clear();
+ ImmDefMIs.clear();
+ bool First = true;
+ MachineBasicBlock::iterator PMII;
for (MachineBasicBlock::iterator
MII = I->begin(), MIE = I->end(); MII != MIE; ) {
MachineInstr *MI = &*MII;
+ LocalMIs.insert(MI);
+
+ if (MI->isLabel() || MI->isPHI() || MI->isImplicitDef() ||
+ MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
+ MI->hasUnmodeledSideEffects()) {
+ ++MII;
+ continue;
+ }
- if (MI->getDesc().isCompare() &&
- !MI->getDesc().hasUnmodeledSideEffects()) {
-#if 0
- if (OptimizeCmpInstr(MI, MBB, MII))
+ const MCInstrDesc &MCID = MI->getDesc();
+
+ if (MCID.isBitcast()) {
+ if (OptimizeBitcastInstr(MI, MBB)) {
+ // MI is deleted.
+ LocalMIs.erase(MI);
+ Changed = true;
+ MII = First ? I->begin() : llvm::next(PMII);
+ continue;
+ }
+ } else if (MCID.isCompare()) {
+ if (OptimizeCmpInstr(MI, MBB)) {
+ // MI is deleted.
+ LocalMIs.erase(MI);
Changed = true;
- else
-#endif
- ++MII;
+ MII = First ? I->begin() : llvm::next(PMII);
+ continue;
+ }
+ }
+
+ if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
+ SeenMoveImm = true;
} else {
Changed |= OptimizeExtInstr(MI, MBB, LocalMIs);
- ++MII;
+ if (SeenMoveImm)
+ Changed |= FoldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
}
+
+ First = false;
+ PMII = MII;
+ ++MII;
}
}
projects / oota-llvm.git / blobdiff