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Simplify code 

Implement InstCombine/mul.ll:test9

llvm-svn: 8488
This commit is contained in:
Chris Lattner 2003-09-11 22:24:54 +00:00
parent 80e8c466fb
commit cce81be1e1
1 changed files with 6 additions and 9 deletions
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15
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
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@ -527,17 +527,14 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
return BinaryOperator::create(Instruction::Mul, SI->getOperand(0),
*CI << *ShOp);
const Type *Ty = CI->getType();
int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
switch (Val) {
case -1: // X * -1 -> -X
if (CI->isNullValue())
return ReplaceInstUsesWith(I, Op1); // X * 0 == 0
if (CI->equalsInt(1)) // X * 1 == X
return ReplaceInstUsesWith(I, Op0);
if (CI->isAllOnesValue()) // X * -1 == 0 - X
return BinaryOperator::createNeg(Op0, I.getName());
case 0:
return ReplaceInstUsesWith(I, Op1); // Eliminate 'mul double %X, 0'
case 1:
return ReplaceInstUsesWith(I, Op0); // Eliminate 'mul int %X, 1'
}
int64_t Val = (int64_t)cast<ConstantInt>(CI)->getRawValue();
if (uint64_t C = Log2(Val)) // Replace X*(2^C) with X << C
return new ShiftInst(Instruction::Shl, Op0,
ConstantUInt::get(Type::UByteTy, C));