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InstCombine: Don't create an unused instruction

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We would create an instruction but not inserting it.
Not inserting the unused instruction would lead us to verification
failure.

This fixes PR21653.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222659 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-11-24 16:41:13 +00:00
parent c19526770e
commit a17a9dc8df
2 changed files with 11 additions and 2 deletions
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3
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -300,8 +300,7 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
if (match(Op0, m_Shl(m_One(), m_Value(Y)))) {
BO = BinaryOperator::CreateShl(Op1, Y);
ShlNSW = cast<BinaryOperator>(Op0)->hasNoSignedWrap();
}
if (match(Op1, m_Shl(m_One(), m_Value(Y)))) {
} else if (match(Op1, m_Shl(m_One(), m_Value(Y)))) {
BO = BinaryOperator::CreateShl(Op0, Y);
ShlNSW = cast<BinaryOperator>(Op1)->hasNoSignedWrap();
}

10
test/Transforms/InstCombine/mul.ll
View File

@ -245,3 +245,13 @@ define i32 @test27(i32 %A, i32 %B) {
ret i32 %D
; CHECK: shl nuw i32 %A, %B
}
define i32 @test28(i32 %A) {
; CHECK-LABEL: @test28(
%B = shl i32 1, %A
%C = mul nsw i32 %B, %B
ret i32 %C
; CHECK: %[[shl1:.*]] = shl i32 1, %A
; CHECK-NEXT: %[[shl2:.*]] = shl i32 %[[shl1]], %A
; CHECK-NEXT: ret i32 %[[shl2]]
}