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Fold select + select where both selects are on the same condition.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124469 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-01-28 03:28:10 +00:00
parent 1ffb533699
commit df3bfae151
2 changed files with 29 additions and 1 deletions
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13
lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -792,6 +792,19 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
if (Instruction *NV = FoldOpIntoPhi(SI))
return NV;
if (SelectInst *TrueSI = dyn_cast<SelectInst>(TrueVal)) {
if (TrueSI->getCondition() == CondVal) {
SI.setOperand(1, TrueSI->getTrueValue());
return &SI;
}
}
if (SelectInst *FalseSI = dyn_cast<SelectInst>(FalseVal)) {
if (FalseSI->getCondition() == CondVal) {
SI.setOperand(2, FalseSI->getFalseValue());
return &SI;
}
}
if (BinaryOperator::isNot(CondVal)) {
SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
SI.setOperand(1, FalseVal);

17
test/Transforms/InstCombine/select.ll
View File

@ -692,7 +692,7 @@ define i64 @test50(i32 %a) nounwind {
; PR8994
; Theis select instruction can't be eliminated because trying to do so would
; This select instruction can't be eliminated because trying to do so would
; change the number of vector elements. This used to assert.
define i48 @test51(<3 x i1> %icmp, <3 x i16> %tmp) {
%select = select <3 x i1> %icmp, <3 x i16> zeroinitializer, <3 x i16> %tmp
@ -700,3 +700,18 @@ define i48 @test51(<3 x i1> %icmp, <3 x i16> %tmp) {
%tmp2 = bitcast <3 x i16> %select to i48
ret i48 %tmp2
}
; PR8575
@g = common global i32 0, align 4
define void @test52(i32 %n, i32 %m) nounwind {
entry:
%cmp = icmp sgt i32 %n, %m
%. = select i1 %cmp, i32 1, i32 3
%add = add nsw i32 %., 3
%storemerge = select i1 %cmp, i32 %., i32 %add
; CHECK: select i1 %cmp, i32 1, i32 6
store i32 %storemerge, i32* @g, align 4
ret void
}