Provide InstCombines for the following 3 cases:
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
diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index b96eb51..1aa51d0 100644
--- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1232,6 +1232,31 @@
}
}
+ // 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);