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Get rid of shifts by zero in most cases.

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llvm-svn: 18931
This commit is contained in:
Brian Gaeke 2004-12-14 08:21:02 +00:00
parent cc0adb0271
commit 83dcf14697
2 changed files with 6 additions and 12 deletions
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7
lib/Target/SparcV8/README.txt
View File

@ -55,13 +55,6 @@ To-do
* support casting 64-bit integers to FP types (fhourstones needs this) * support casting 64-bit integers to FP types (fhourstones needs this)
* support FP rem (call fmod) * support FP rem (call fmod)
* Eliminate srl/sll by zero bits like this:
sll %l0, 0, %l0
srl %l0, 0, %o0
We think these are only used by V9 to clear off the top 32 bits of a reg,
so they are not needed.
* Keep the address of the constant pool in a register instead of forming its * Keep the address of the constant pool in a register instead of forming its
address all of the time. address all of the time.

11
lib/Target/SparcV8/SparcV8ISelSimple.cpp
View File

@ -71,7 +71,8 @@ namespace {
unsigned emitIntegerCast (MachineBasicBlock *BB, unsigned emitIntegerCast (MachineBasicBlock *BB,
MachineBasicBlock::iterator IP, MachineBasicBlock::iterator IP,
const Type *oldTy, unsigned SrcReg, const Type *oldTy, unsigned SrcReg,
const Type *newTy, unsigned DestReg); const Type *newTy, unsigned DestReg,
bool castToLong = false);
void emitFPToIntegerCast (MachineBasicBlock *BB, void emitFPToIntegerCast (MachineBasicBlock *BB,
MachineBasicBlock::iterator IP, const Type *oldTy, MachineBasicBlock::iterator IP, const Type *oldTy,
unsigned SrcReg, const Type *newTy, unsigned SrcReg, const Type *newTy,
@ -606,15 +607,15 @@ void V8ISel::visitCastInst(CastInst &I) {
unsigned V8ISel::emitIntegerCast (MachineBasicBlock *BB, unsigned V8ISel::emitIntegerCast (MachineBasicBlock *BB,
MachineBasicBlock::iterator IP, const Type *oldTy, MachineBasicBlock::iterator IP, const Type *oldTy,
unsigned SrcReg, const Type *newTy, unsigned SrcReg, const Type *newTy,
unsigned DestReg) { unsigned DestReg, bool castToLong) {
if (oldTy == newTy) { unsigned shiftWidth = 32 - (8 * TM.getTargetData ().getTypeSize (newTy));
if (oldTy == newTy || (!castToLong && shiftWidth == 0)) {
// No-op cast - just emit a copy; assume the reg. allocator will zap it. // No-op cast - just emit a copy; assume the reg. allocator will zap it.
BuildMI (*BB, IP, V8::ORrr, 2, DestReg).addReg (V8::G0).addReg(SrcReg); BuildMI (*BB, IP, V8::ORrr, 2, DestReg).addReg (V8::G0).addReg(SrcReg);
return SrcReg; return SrcReg;
} }
// Emit left-shift, then right-shift to sign- or zero-extend. // Emit left-shift, then right-shift to sign- or zero-extend.
unsigned TmpReg = makeAnotherReg (newTy); unsigned TmpReg = makeAnotherReg (newTy);
unsigned shiftWidth = 32 - (8 * TM.getTargetData ().getTypeSize (newTy));
BuildMI (*BB, IP, V8::SLLri, 2, TmpReg).addZImm (shiftWidth).addReg(SrcReg); BuildMI (*BB, IP, V8::SLLri, 2, TmpReg).addZImm (shiftWidth).addReg(SrcReg);
if (newTy->isSigned ()) { // sign-extend with SRA if (newTy->isSigned ()) { // sign-extend with SRA
BuildMI(*BB, IP, V8::SRAri, 2, DestReg).addZImm (shiftWidth).addReg(TmpReg); BuildMI(*BB, IP, V8::SRAri, 2, DestReg).addZImm (shiftWidth).addReg(TmpReg);
@ -739,7 +740,7 @@ void V8ISel::emitCastOperation(MachineBasicBlock *BB,
const Type *OldHalfTy = oldTy->isSigned() ? Type::IntTy : Type::UIntTy; const Type *OldHalfTy = oldTy->isSigned() ? Type::IntTy : Type::UIntTy;
const Type *NewHalfTy = newTy->isSigned() ? Type::IntTy : Type::UIntTy; const Type *NewHalfTy = newTy->isSigned() ? Type::IntTy : Type::UIntTy;
unsigned TempReg = emitIntegerCast (BB, IP, OldHalfTy, SrcReg, unsigned TempReg = emitIntegerCast (BB, IP, OldHalfTy, SrcReg,
NewHalfTy, DestReg+1); NewHalfTy, DestReg+1, true);
if (newTy->isSigned ()) { if (newTy->isSigned ()) {
BuildMI (*BB, IP, V8::SRAri, 2, DestReg).addReg (TempReg) BuildMI (*BB, IP, V8::SRAri, 2, DestReg).addReg (TempReg)
.addZImm (31); .addZImm (31);