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teach instsimplify to transform (X / Y) * Y to X

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when the div is an exact udiv.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124994 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2011-02-06 22:05:31 +00:00
parent c35a44d3d7
commit c6ee9181a5
2 changed files with 25 additions and 3 deletions
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8
lib/Analysis/InstructionSimplify.cpp
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@ -735,9 +735,11 @@ static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
// (X / Y) * Y -> X if the division is exact.
Value *X = 0, *Y = 0;
if ((match(Op0, m_SDiv(m_Value(X), m_Value(Y))) && Y == Op1) || // (X / Y) * Y
(match(Op1, m_SDiv(m_Value(X), m_Value(Y))) && Y == Op0)) { // Y * (X / Y)
BinaryOperator *SDiv = cast<BinaryOperator>(Y == Op1 ? Op0 : Op1);
if (SDiv->isExact())
(match(Op0, m_UDiv(m_Value(X), m_Value(Y))) && Y == Op1) ||
(match(Op1, m_SDiv(m_Value(X), m_Value(Y))) && Y == Op0) || // Y * (X / Y)
(match(Op1, m_UDiv(m_Value(X), m_Value(Y))) && Y == Op0)) {
BinaryOperator *Div = cast<BinaryOperator>(Y == Op1 ? Op0 : Op1);
if (Div->isExact())
return X;
}

20
test/Transforms/InstSimplify/reassociate.ll
View File

@ -137,6 +137,7 @@ define i32 @sdiv5(i32 %x, i32 %y) {
; CHECK: ret i32 %x
}
define i32 @udiv1(i32 %x, i32 %y) {
; CHECK: @udiv1
; (no overflow X * Y) / Y -> X
@ -164,3 +165,22 @@ define i32 @udiv3(i32 %x, i32 %y) {
ret i32 %div
; CHECK: ret i32 0
}
define i32 @udiv4(i32 %x, i32 %y) {
; CHECK: @udiv4
; (X / Y) * Y -> X if the division is exact
%div = udiv exact i32 %x, %y
%mul = mul i32 %div, %y
ret i32 %mul
; CHECK: ret i32 %x
}
define i32 @udiv5(i32 %x, i32 %y) {
; CHECK: @udiv5
; Y * (X / Y) -> X if the division is exact
%div = udiv exact i32 %x, %y
%mul = mul i32 %y, %div
ret i32 %mul
; CHECK: ret i32 %x
}