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implement rdar://7293527, a trivial instcombine that llvm-gcc

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gets but clang doesn't, because it is implemented in GCC's
fold routine.

llvm-svn: 83761
This commit is contained in:
Chris Lattner 2009-10-11 07:53:15 +00:00
parent 2a0366af9e
commit 601cc4c588
2 changed files with 20 additions and 1 deletions
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13
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2661,7 +2661,7 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
if (isa<UndefValue>(I.getOperand(1))) // undef * X -> 0
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
// Simplify mul instructions with a constant RHS...
// Simplify mul instructions with a constant RHS.
if (Constant *Op1 = dyn_cast<Constant>(I.getOperand(1))) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
@ -2765,9 +2765,20 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
}
}
/// i1 mul -> i1 and.
if (I.getType() == Type::getInt1Ty(*Context))
return BinaryOperator::CreateAnd(Op0, I.getOperand(1));
// X*(1 << Y) --> X << Y
// (1 << Y)*X --> X << Y
{
Value *Y;
if (match(Op0, m_Shl(m_One(), m_Value(Y))))
return BinaryOperator::CreateShl(I.getOperand(1), Y);
if (match(I.getOperand(1), m_Shl(m_One(), m_Value(Y))))
return BinaryOperator::CreateShl(Op0, Y);
}
// 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

8
test/Transforms/InstCombine/mul.ll
View File

@ -88,3 +88,11 @@ define <16 x i8> @test14(<16 x i8> %a) {
%b = mul <16 x i8> %a, zeroinitializer
ret <16 x i8> %b
}
; rdar://7293527
define i32 @test15(i32 %A, i32 %B) {
entry:
%shl = shl i32 1, %B
%m = mul i32 %shl, %A
ret i32 %m
}