[InstCombine] Fold icmp eq/ne (and %x, signbit), 0 -> %x s>=/s< 0 earlier
Summary:
To generate simplified IR, make sure fold
```
(X & signbit) ==/!= 0) -> X s>=/s< 0;
```
is scheduled before fold
```
((X << Y) & C) == 0 -> (X & (C >> Y)) == 0.
```
https://rise4fun.com/Alive/fbdh
Reviewers: lebedev.ri, efriedma, spatel, craig.topper
Reviewed By: lebedev.ri
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D63026
llvm-svn: 363845
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 0cfd930..5493b4a 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1626,20 +1626,34 @@
Instruction *InstCombiner::foldICmpAndConstConst(ICmpInst &Cmp,
BinaryOperator *And,
const APInt &C1) {
+ bool isICMP_NE = Cmp.getPredicate() == ICmpInst::ICMP_NE;
+
// For vectors: icmp ne (and X, 1), 0 --> trunc X to N x i1
// TODO: We canonicalize to the longer form for scalars because we have
// better analysis/folds for icmp, and codegen may be better with icmp.
- if (Cmp.getPredicate() == CmpInst::ICMP_NE && Cmp.getType()->isVectorTy() &&
- C1.isNullValue() && match(And->getOperand(1), m_One()))
+ if (isICMP_NE && Cmp.getType()->isVectorTy() && C1.isNullValue() &&
+ match(And->getOperand(1), m_One()))
return new TruncInst(And->getOperand(0), Cmp.getType());
const APInt *C2;
- if (!match(And->getOperand(1), m_APInt(C2)))
+ Value *X;
+ if (!match(And, m_And(m_Value(X), m_APInt(C2))))
return nullptr;
+ // Don't perform the following transforms if the AND has multiple uses
if (!And->hasOneUse())
return nullptr;
+ if (Cmp.isEquality() && C1.isNullValue()) {
+ // Restrict this fold to single-use 'and' (PR10267).
+ // Replace (and X, (1 << size(X)-1) != 0) with X s< 0
+ if (C2->isSignMask()) {
+ Constant *Zero = Constant::getNullValue(X->getType());
+ auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
+ return new ICmpInst(NewPred, X, Zero);
+ }
+ }
+
// If the LHS is an 'and' of a truncate and we can widen the and/compare to
// the input width without changing the value produced, eliminate the cast:
//
@@ -2788,13 +2802,6 @@
if (!BO->hasOneUse())
break;
- // Replace (and X, (1 << size(X)-1) != 0) with x s< 0
- if (BOC->isSignMask()) {
- Constant *Zero = Constant::getNullValue(BOp0->getType());
- auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
- return new ICmpInst(NewPred, BOp0, Zero);
- }
-
// ((X & ~7) == 0) --> X < 8
if (C.isNullValue() && (~(*BOC) + 1).isPowerOf2()) {
Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));