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InstCombine: Preserve nsw/nuw for ((X << C2)*C1) -> (X * (C1 << C2))

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222605 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-11-22 04:52:52 +00:00
parent 0f8991742c
commit 156d6ec86b
2 changed files with 28 additions and 3 deletions
lib/Transforms/InstCombine
InstCombineMulDivRem.cpp
test/Transforms/InstCombine
mul.ll

15
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@ -151,9 +151,18 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
const APInt *IVal;
if (match(&I, m_Mul(m_Shl(m_Value(NewOp), m_Constant(C2)),
m_Constant(C1))) &&
match(C1, m_APInt(IVal)))
// ((X << C1)*C2) == (X * (C2 << C1))
return BinaryOperator::CreateMul(NewOp, ConstantExpr::getShl(C1, C2));
match(C1, m_APInt(IVal))) {
// ((X << C2)*C1) == (X * (C1 << C2))
Constant *Shl = ConstantExpr::getShl(C1, C2);
BinaryOperator *Mul = cast<BinaryOperator>(I.getOperand(0));
BinaryOperator *BO = BinaryOperator::CreateMul(NewOp, Shl);
if (I.hasNoUnsignedWrap() && Mul->hasNoUnsignedWrap())
BO->setHasNoUnsignedWrap();
if (I.hasNoSignedWrap() && Mul->hasNoSignedWrap() &&
Shl->isNotMinSignedValue())
BO->setHasNoSignedWrap();
return BO;
}
if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
Constant *NewCst = nullptr;

16
test/Transforms/InstCombine/mul.ll

@ -204,3 +204,19 @@ define i32 @test22(i32 %A) {
ret i32 %B
; CHECK: sub nsw i32 0, %A
}
define i32 @test23(i32 %A) {
; CHECK-LABEL: @test23(
%B = shl nuw i32 %A, 1
%C = mul nuw i32 %B, 3
ret i32 %C
; CHECK: mul nuw i32 %A, 6
}
define i32 @test24(i32 %A) {
; CHECK-LABEL: @test24(
%B = shl nsw i32 %A, 1
%C = mul nsw i32 %B, 3
ret i32 %C
; CHECK: mul nsw i32 %A, 6
}