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Implement InstCombine/mul.ll:test10, which is a case that occurs when dealing

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with "predication"


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11734 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-02-23 05:39:21 +00:00
parent 1dda055e55
commit fb54b2b744
1 changed files with 40 additions and 0 deletions
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40
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -599,6 +599,46 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
if (Value *Op1v = dyn_castNegVal(I.getOperand(1)))
return BinaryOperator::create(Instruction::Mul, Op0v, Op1v);
// If one of the operands of the multiply is a cast from a boolean value, then
// we know the bool is either zero or one, so this is a 'masking' multiply.
// See if we can simplify things based on how the boolean was originally
// formed.
CastInst *BoolCast = 0;
if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(0)))
if (CI->getOperand(0)->getType() == Type::BoolTy)
BoolCast = CI;
if (!BoolCast)
if (CastInst *CI = dyn_cast<CastInst>(I.getOperand(1)))
if (CI->getOperand(0)->getType() == Type::BoolTy)
BoolCast = CI;
if (BoolCast) {
if (SetCondInst *SCI = dyn_cast<SetCondInst>(BoolCast->getOperand(0))) {
Value *SCIOp0 = SCI->getOperand(0), *SCIOp1 = SCI->getOperand(1);
const Type *SCOpTy = SCIOp0->getType();
// If the source is X < 0, and X is a signed integer type, convert this
// multiply into a shift/and combination.
if (SCI->getOpcode() == Instruction::SetLT &&
isa<Constant>(SCIOp1) && cast<Constant>(SCIOp1)->isNullValue() &&
SCOpTy->isInteger() && SCOpTy->isSigned()) {
// Shift the X value right to turn it into "all signbits".
Constant *Amt = ConstantUInt::get(Type::UByteTy,
SCOpTy->getPrimitiveSize()*8-1);
Value *V = new ShiftInst(Instruction::Shr, SCIOp0, Amt,
BoolCast->getName()+".mask", &I);
// If the multiply type is not the same as the source type, sign extend
// or truncate to the multiply type.
if (I.getType() != V->getType())
V = new CastInst(V, I.getType(), V->getName(), &I);
Value *OtherOp = Op0 == BoolCast ? I.getOperand(1) : Op0;
return BinaryOperator::create(Instruction::And, V, OtherOp);
}
}
}
return Changed ? &I : 0;
}