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InstCombine: Propagate exact in (udiv (lshr X,C1),C2) -> (udiv x,C1<<C2)

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222620 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2014-11-22 18:16:54 +00:00
parent e915b4b7c8
commit 218fe23f41
2 changed files with 16 additions and 2 deletions
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9
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -997,9 +997,14 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
match(Op1, m_APInt(C2))) {
bool Overflow;
APInt C2ShlC1 = C2->ushl_ov(*C1, Overflow);
if (!Overflow)
return BinaryOperator::CreateUDiv(
if (!Overflow) {
bool IsExact = I.isExact() && match(Op0, m_Exact(m_Value()));
BinaryOperator *BO = BinaryOperator::CreateUDiv(
X, ConstantInt::get(X->getType(), C2ShlC1));
if (IsExact)
BO->setIsExact();
return BO;
}
}
}

9
test/Transforms/InstCombine/div.ll
View File

@ -286,3 +286,12 @@ define i32 @test32(i32 %a, i32 %b) {
; CHECK-NEXT: %[[div:.*]] = udiv i32 %a, %[[shr]]
; CHECK-NEXT: ret i32
}
define <2 x i64> @test33(<2 x i64> %x) nounwind {
%shr = lshr exact <2 x i64> %x, <i64 5, i64 5>
%div = udiv exact <2 x i64> %shr, <i64 6, i64 6>
ret <2 x i64> %div
; CHECK-LABEL: @test33(
; CHECK-NEXT: udiv exact <2 x i64> %x, <i64 192, i64 192>
; CHECK-NEXT: ret <2 x i64>
}