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Add the select optimization recently added to instcombine to constant folding.

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This is the one where one of the branches of the select is another select on
the same condition.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124547 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-01-29 20:35:06 +00:00
parent 337c081138
commit 175e7aec13
2 changed files with 21 additions and 0 deletions
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12
lib/VMCore/ConstantFold.cpp
View File

@ -693,6 +693,18 @@ Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
if (isa<UndefValue>(V2)) return V1;
if (isa<UndefValue>(Cond)) return V1;
if (V1 == V2) return V1;
if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
if (TrueVal->getOpcode() == Instruction::Select)
if (TrueVal->getOperand(0) == Cond)
return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
}
if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
if (FalseVal->getOpcode() == Instruction::Select)
if (FalseVal->getOperand(0) == Cond)
return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
}
return 0;
}

9
test/Transforms/ConstProp/constant-expr.ll
View File

@ -100,3 +100,12 @@
; CHECK: pr9011_14 = constant i128 0
@pr9011_15 = constant i128 bitcast (<4 x i32> zeroinitializer to i128)
; CHECK: pr9011_15 = constant i128 0
@select = internal constant
i32 select (i1 icmp ult (i32 ptrtoint (i8* @X to i32),
i32 ptrtoint (i8* @Y to i32)),
i32 select (i1 icmp ult (i32 ptrtoint (i8* @X to i32),
i32 ptrtoint (i8* @Y to i32)),
i32 10, i32 20),
i32 30)
; CHECK: select = internal constant i32 select {{.*}} i32 10, i32 30