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Kill a majority of unnecessary sign extensions for byte loads

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15991 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nate Begeman 2004-08-22 08:10:15 +00:00
parent 1f4a132599
commit 0e5e5f56bd
1 changed files with 30 additions and 12 deletions
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42
lib/Target/PowerPC/PPC32ISelSimple.cpp
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@ -32,9 +32,6 @@
using namespace llvm;
namespace {
Statistic<> GEPFolds("ppc-codegen", "Number of GEPs folded");
Statistic<> NumSetCC("ppc-codegen", "Number of SetCC straight-lined");
/// TypeClass - Used by the PowerPC backend to group LLVM types by their basic
/// PPC Representation.
///
@ -283,7 +280,7 @@ namespace {
unsigned ExtendOrClear(MachineBasicBlock *MBB,
MachineBasicBlock::iterator IP,
unsigned Reg, const Type *CompTy);
Value *Op0, Value *Op1);
/// promote32 - Make a value 32-bits wide, and put it somewhere.
///
@ -917,13 +914,11 @@ static GetElementPtrInst *canFoldGEPIntoLoadOrStore(Value *V) {
GEPI->getParent() == User->getParent() &&
User->getOperand(0) != GEPI &&
User->getOperand(1) == GEPI) {
++GEPFolds;
return GEPI;
}
if (isa<LoadInst>(User) &&
GEPI->getParent() == User->getParent() &&
User->getOperand(0) == GEPI) {
++GEPFolds;
return GEPI;
}
}
@ -966,7 +961,9 @@ void ISel::emitUCOM(MachineBasicBlock *MBB, MachineBasicBlock::iterator IP,
unsigned ISel::ExtendOrClear(MachineBasicBlock *MBB,
MachineBasicBlock::iterator IP,
unsigned Reg, const Type *CompTy) {
Value *Op0, Value *Op1) {
const Type *CompTy = Op0->getType();
unsigned Reg = getReg(Op0, MBB, IP);
unsigned Class = getClassB(CompTy);
// Before we do a comparison or SetCC, we have to make sure that we truncate
@ -1000,7 +997,7 @@ unsigned ISel::EmitComparison(unsigned OpNum, Value *Op0, Value *Op1,
// The arguments are already supposed to be of the same type.
const Type *CompTy = Op0->getType();
unsigned Class = getClassB(CompTy);
unsigned Op0r = ExtendOrClear(MBB, IP, getReg(Op0, MBB, IP), CompTy);
unsigned Op0r = ExtendOrClear(MBB, IP, Op0, Op1);
// Use crand for lt, gt and crandc for le, ge
unsigned CROpcode = (OpNum == 2 || OpNum == 4) ? PPC::CRAND : PPC::CRANDC;
@ -2384,6 +2381,27 @@ void ISel::emitShiftOperation(MachineBasicBlock *MBB,
}
}
/// LoadNeedsSignExtend - On PowerPC, there is no load byte with sign extend.
/// Therefore, if this is a byte load and the destination type is signed, we
/// would normall need to also emit a sign extend instruction after the load.
/// However, store instructions don't care whether a signed type was sign
/// extended across a whole register. Also, a SetCC instruction will emit its
/// own sign extension to force the value into the appropriate range, so we
/// need not emit it here. Ideally, this kind of thing wouldn't be necessary
/// once LLVM's type system is improved.
static bool LoadNeedsSignExtend(LoadInst &LI) {
if (cByte == getClassB(LI.getType()) && LI.getType()->isSigned()) {
bool AllUsesAreStoresOrSetCC = true;
for (Value::use_iterator I = LI.use_begin(), E = LI.use_end(); I != E; ++I)
if (!isa<StoreInst>(*I) && !isa<SetCondInst>(*I)) {
AllUsesAreStoresOrSetCC = false;
break;
}
if (!AllUsesAreStoresOrSetCC)
return true;
}
return false;
}
/// visitLoadInst - Implement LLVM load instructions. Pretty straightforward
/// mapping of LLVM classes to PPC load instructions, with the exception of
@ -2415,7 +2433,7 @@ void ISel::visitLoadInst(LoadInst &I) {
if (Class == cLong) {
addFrameReference(BuildMI(BB, ImmOpcode, 2, DestReg), FI);
addFrameReference(BuildMI(BB, ImmOpcode, 2, DestReg+1), FI, 4);
} else if (Class == cByte && I.getType()->isSigned()) {
} else if (LoadNeedsSignExtend(I)) {
unsigned TmpReg = makeAnotherReg(I.getType());
addFrameReference(BuildMI(BB, ImmOpcode, 2, TmpReg), FI);
BuildMI(BB, PPC::EXTSB, 1, DestReg).addReg(TmpReg);
@ -2441,7 +2459,7 @@ void ISel::visitLoadInst(LoadInst &I) {
if (pendingAdd == 0 && Class != cLong &&
canUseAsImmediateForOpcode(offset, 0)) {
if (Class == cByte && I.getType()->isSigned()) {
if (LoadNeedsSignExtend(I)) {
unsigned TmpReg = makeAnotherReg(I.getType());
BuildMI(BB, ImmOpcode, 2, TmpReg).addSImm(offset->getValue())
.addReg(baseReg);
@ -2460,7 +2478,7 @@ void ISel::visitLoadInst(LoadInst &I) {
BuildMI(BB, PPC::ADDI, 2, indexPlus4).addReg(indexReg).addSImm(4);
BuildMI(BB, IdxOpcode, 2, DestReg).addReg(indexReg).addReg(baseReg);
BuildMI(BB, IdxOpcode, 2, DestReg+1).addReg(indexPlus4).addReg(baseReg);
} else if (Class == cByte && I.getType()->isSigned()) {
} else if (LoadNeedsSignExtend(I)) {
unsigned TmpReg = makeAnotherReg(I.getType());
BuildMI(BB, IdxOpcode, 2, TmpReg).addReg(indexReg).addReg(baseReg);
BuildMI(BB, PPC::EXTSB, 1, DestReg).addReg(TmpReg);
@ -2477,7 +2495,7 @@ void ISel::visitLoadInst(LoadInst &I) {
if (Class == cLong) {
BuildMI(BB, ImmOpcode, 2, DestReg).addSImm(0).addReg(SrcAddrReg);
BuildMI(BB, ImmOpcode, 2, DestReg+1).addSImm(4).addReg(SrcAddrReg);
} else if (Class == cByte && I.getType()->isSigned()) {
} else if (LoadNeedsSignExtend(I)) {
unsigned TmpReg = makeAnotherReg(I.getType());
BuildMI(BB, ImmOpcode, 2, TmpReg).addSImm(0).addReg(SrcAddrReg);
BuildMI(BB, PPC::EXTSB, 1, DestReg).addReg(TmpReg);