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Provide InstCombines for the following 3 cases:

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A * (1 - (uitofp i1 C)) -> select C, 0, A
B * (uitofp i1 C) -> select C, B, 0
select C, 0, A + select C, B, 0 -> select C, B, A

These come up in code that has been hand-optimized from a select to a linear blend, 
on platforms where that may have mattered. We want to undo such changes 
with the following transform:
A*(1 - uitofp i1 C) + B*(uitofp i1 C) -> select C, A, B



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181216 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jean-Luc Duprat
2013-05-06 16:55:50 +00:00
parent 4c8850cd1c
commit c5cf6e5365
4 changed files with 93 additions and 0 deletions
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25
lib/Transforms/InstCombine/InstCombineAddSub.cpp
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@@ -1232,6 +1232,31 @@ Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
}
}
// select C, 0, B + select C, A, 0 -> select C, A, B
{
Value *A1, *B1, *C1, *A2, *B2, *C2;
if (match(LHS, m_Select(m_Value(C1), m_Value(A1), m_Value(B1))) &&
match(RHS, m_Select(m_Value(C2), m_Value(A2), m_Value(B2)))) {
if (C1 == C2) {
Constant *Z1=0, *Z2=0;
Value *A, *B, *C=C1;
if (match(A1, m_AnyZero()) && match(B2, m_AnyZero())) {
Z1 = dyn_cast<Constant>(A1); A = A2;
Z2 = dyn_cast<Constant>(B2); B = B1;
} else if (match(B1, m_AnyZero()) && match(A2, m_AnyZero())) {
Z1 = dyn_cast<Constant>(B1); B = B2;
Z2 = dyn_cast<Constant>(A2); A = A1;
}
if (Z1 && Z2 &&
(I.hasNoSignedZeros() ||
(Z1->isNegativeZeroValue() && Z2->isNegativeZeroValue()))) {
return SelectInst::Create(C, A, B);
}
}
}
}
if (I.hasUnsafeAlgebra()) {
if (Value *V = FAddCombine(Builder).simplify(&I))
return ReplaceInstUsesWith(I, V);