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InstCombine: Propagate NSW for -X * -Y -> X * Y 

llvm-svn: 222612
This commit is contained in:
David Majnemer 2014-11-22 07:25:19 +00:00
parent 4efa9ff8ca
commit 8279a7506d
2 changed files with 19 additions and 3 deletions
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13
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -237,9 +237,16 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
}
}
if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
if (Value *Op1v = dyn_castNegVal(Op1))
return BinaryOperator::CreateMul(Op0v, Op1v);
if (Value *Op0v = dyn_castNegVal(Op0)) { // -X * -Y = X*Y
if (Value *Op1v = dyn_castNegVal(Op1)) {
BinaryOperator *BO = BinaryOperator::CreateMul(Op0v, Op1v);
if (I.hasNoSignedWrap() &&
match(Op0, m_NSWSub(m_Value(), m_Value())) &&
match(Op1, m_NSWSub(m_Value(), m_Value())))
BO->setHasNoSignedWrap();
return BO;
}
}
// (X / Y) * Y = X - (X % Y)
// (X / Y) * -Y = (X % Y) - X

9
llvm/test/Transforms/InstCombine/mul.ll
View File

@ -220,3 +220,12 @@ define i32 @test24(i32 %A) {
ret i32 %C
; CHECK: mul nsw i32 %A, 6
}
define i32 @test25(i32 %A, i32 %B) {
; CHECK-LABEL: @test25(
%C = sub nsw i32 0, %A
%D = sub nsw i32 0, %B
%E = mul nsw i32 %C, %D
ret i32 %E
; CHECK: mul nsw i32 %A, %B
}