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Implement InstCombine/cast-set.ll:test6[a]. This improves code generated for 

a hot function in em3d

llvm-svn: 9673
This commit is contained in:
Chris Lattner 2003-11-03 05:17:03 +00:00
parent 11bea4f7c7
commit 6444c37488
1 changed files with 57 additions and 6 deletions
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63
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1258,21 +1258,22 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
// Test to see if the operands of the setcc are casted versions of other
// values. If the cast can be stripped off both arguments, we do so now.
if (CastInst *CI = dyn_cast<CastInst>(Op0))
if (CI->getOperand(0)->getType()->isLosslesslyConvertibleTo(CI->getType())&&
if (CastInst *CI = dyn_cast<CastInst>(Op0)) {
Value *CastOp0 = CI->getOperand(0);
if (CastOp0->getType()->isLosslesslyConvertibleTo(CI->getType()) &&
!isa<Argument>(Op1) &&
(I.getOpcode() == Instruction::SetEQ ||
I.getOpcode() == Instruction::SetNE)) {
// We keep moving the cast from the left operand over to the right
// operand, where it can often be eliminated completely.
Op0 = CI->getOperand(0);
Op0 = CastOp0;
// If operand #1 is a cast instruction, see if we can eliminate it as
// well.
if (CastInst *CI = dyn_cast<CastInst>(Op1))
if (CI->getOperand(0)->getType()->isLosslesslyConvertibleTo(
if (CastInst *CI2 = dyn_cast<CastInst>(Op1))
if (CI2->getOperand(0)->getType()->isLosslesslyConvertibleTo(
Op0->getType()))
Op1 = CI->getOperand(0);
Op1 = CI2->getOperand(0);
// If Op1 is a constant, we can fold the cast into the constant.
if (Op1->getType() != Op0->getType())
@ -1286,6 +1287,56 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) {
return BinaryOperator::create(I.getOpcode(), Op0, Op1);
}
// Handle the special case of: setcc (cast bool to X), <cst>
// This comes up when you have code like
// int X = A < B;
// if (X) ...
// For generality, we handle any zero-extension of any operand comparison
// with a constant.
if (ConstantInt *ConstantRHS = dyn_cast<ConstantInt>(Op1)) {
const Type *SrcTy = CastOp0->getType();
const Type *DestTy = Op0->getType();
if (SrcTy->getPrimitiveSize() < DestTy->getPrimitiveSize() &&
(SrcTy->isUnsigned() || SrcTy == Type::BoolTy)) {
// Ok, we have an expansion of operand 0 into a new type. Get the
// constant value, masink off bits which are not set in the RHS. These
// could be set if the destination value is signed.
uint64_t ConstVal = ConstantRHS->getRawValue();
ConstVal &= (1ULL << DestTy->getPrimitiveSize()*8)-1;
// If the constant we are comparing it with has high bits set, which
// don't exist in the original value, the values could never be equal,
// because the source would be zero extended.
unsigned SrcBits =
SrcTy == Type::BoolTy ? 1 : SrcTy->getPrimitiveSize()*8;
bool HasSignBit = 1ULL << (DestTy->getPrimitiveSize()*8-1);
if (ConstVal & ((1ULL << SrcBits)-1)) {
switch (I.getOpcode()) {
default: assert(0 && "Unknown comparison type!");
case Instruction::SetEQ:
return ReplaceInstUsesWith(I, ConstantBool::False);
case Instruction::SetNE:
return ReplaceInstUsesWith(I, ConstantBool::True);
case Instruction::SetLT:
case Instruction::SetLE:
if (DestTy->isSigned() && HasSignBit)
return ReplaceInstUsesWith(I, ConstantBool::False);
return ReplaceInstUsesWith(I, ConstantBool::True);
case Instruction::SetGT:
case Instruction::SetGE:
if (DestTy->isSigned() && HasSignBit)
return ReplaceInstUsesWith(I, ConstantBool::True);
return ReplaceInstUsesWith(I, ConstantBool::False);
}
}
// Otherwise, we can replace the setcc with a setcc of the smaller
// operand value.
Op1 = ConstantExpr::getCast(cast<Constant>(Op1), SrcTy);
return BinaryOperator::create(I.getOpcode(), CastOp0, Op1);
}
}
}
return Changed ? &I : 0;
}