[InstCombine] Fold icmp eq/ne (and %x, C), 0 iff (-C) is power of two -> %x u</u>= (-C) earlier.
Summary:
To generate simplified IR, make sure fold
(X & ~C) ==/!= 0 --> X u</u>= C+1
is scheduled before fold
((X << Y) & C) == 0 -> (X & (C >> Y)) == 0.
https://rise4fun.com/Alive/7ZN
Reviewers: lebedev.ri, efriedma, spatel, craig.topper
Reviewed By: lebedev.ri
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D63505
llvm-svn: 364255
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 78d9129..0a6c5a3 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1652,6 +1652,15 @@
auto NewPred = isICMP_NE ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_SGE;
return new ICmpInst(NewPred, X, Zero);
}
+
+ // Restrict this fold only for single-use 'and' (PR10267).
+ // ((%x & C) == 0) --> %x u< (-C) iff (-C) is power of two.
+ if ((~(*C2) + 1).isPowerOf2()) {
+ Constant *NegBOC =
+ ConstantExpr::getNeg(cast<Constant>(And->getOperand(1)));
+ auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
+ return new ICmpInst(NewPred, X, NegBOC);
+ }
}
// If the LHS is an 'and' of a truncate and we can widen the and/compare to
@@ -2797,17 +2806,6 @@
if (C == *BOC && C.isPowerOf2())
return new ICmpInst(isICMP_NE ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE,
BO, Constant::getNullValue(RHS->getType()));
-
- // Don't perform the following transforms if the AND has multiple uses
- if (!BO->hasOneUse())
- break;
-
- // ((X & ~7) == 0) --> X < 8
- if (C.isNullValue() && (~(*BOC) + 1).isPowerOf2()) {
- Constant *NegBOC = ConstantExpr::getNeg(cast<Constant>(BOp1));
- auto NewPred = isICMP_NE ? ICmpInst::ICMP_UGE : ICmpInst::ICMP_ULT;
- return new ICmpInst(NewPred, BOp0, NegBOC);
- }
}
break;
}