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

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

llvm-svn: 124547
This commit is contained in:
Nick Lewycky 2011-01-29 20:35:06 +00:00
parent 265aa7c070
commit 97a2895e73
2 changed files with 21 additions and 0 deletions
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12
llvm/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
llvm/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