Move folding of icmp with zero after checking for min/max idioms.
Summary:
The following transformation for cmp instruction:
icmp smin(x, PositiveValue), 0 -> icmp x, 0
should only be done after checking for min/max to prevent infinite
looping caused by a reverse canonicalization. That is why this
transformation was moved to place after the mentioned check.
Reviewers: spatel, efriedma
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38934
Patch by: Artur Gainullin <artur.gainullin@intel.com>
llvm-svn: 315895
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index c3a3c4f..04ae43a 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1318,6 +1318,24 @@
return ExtractValueInst::Create(Call, 1, "sadd.overflow");
}
+// Handle (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
+Instruction *InstCombiner::foldICmpWithZero(ICmpInst &Cmp) {
+ CmpInst::Predicate Pred = Cmp.getPredicate();
+ Value *X = Cmp.getOperand(0);
+
+ if (match(Cmp.getOperand(1), m_Zero()) && Pred == ICmpInst::ICMP_SGT) {
+ Value *A, *B;
+ SelectPatternResult SPR = matchSelectPattern(X, A, B);
+ if (SPR.Flavor == SPF_SMIN) {
+ if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
+ return new ICmpInst(Pred, B, Cmp.getOperand(1));
+ if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
+ return new ICmpInst(Pred, A, Cmp.getOperand(1));
+ }
+ }
+ return nullptr;
+}
+
// Fold icmp Pred X, C.
Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
CmpInst::Predicate Pred = Cmp.getPredicate();
@@ -1349,17 +1367,6 @@
return Res;
}
- // (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
- if (C->isNullValue() && Pred == ICmpInst::ICMP_SGT) {
- SelectPatternResult SPR = matchSelectPattern(X, A, B);
- if (SPR.Flavor == SPF_SMIN) {
- if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
- return new ICmpInst(Pred, B, Cmp.getOperand(1));
- if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
- return new ICmpInst(Pred, A, Cmp.getOperand(1));
- }
- }
-
// FIXME: Use m_APInt to allow folds for splat constants.
ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
if (!CI)
@@ -4462,6 +4469,10 @@
(SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
return nullptr;
+ // Do this after checking for min/max to prevent infinite looping.
+ if (Instruction *Res = foldICmpWithZero(I))
+ return Res;
+
// FIXME: We only do this after checking for min/max to prevent infinite
// looping caused by a reverse canonicalization of these patterns for min/max.
// FIXME: The organization of folds is a mess. These would naturally go into
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 88ce4de..10385b0 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -700,6 +700,7 @@
Instruction *foldICmpInstWithConstantNotInt(ICmpInst &Cmp);
Instruction *foldICmpBinOp(ICmpInst &Cmp);
Instruction *foldICmpEquality(ICmpInst &Cmp);
+ Instruction *foldICmpWithZero(ICmpInst &Cmp);
Instruction *foldICmpSelectConstant(ICmpInst &Cmp, SelectInst *Select,
ConstantInt *C);