[InstSimplify] simplifyUnsignedRangeCheck(): handle more cases (PR43251)
Summary:
I don't have a direct motivational case for this,
but it would be good to have this for completeness/symmetry.
This pattern is basically the motivational pattern from
https://bugs.llvm.org/show_bug.cgi?id=43251
but with different predicate that requires that the offset is non-zero.
The completeness bit comes from the fact that a similar pattern (offset != zero)
will be needed for https://bugs.llvm.org/show_bug.cgi?id=43259,
so it'd seem to be good to not overlook very similar patterns..
Proofs: https://rise4fun.com/Alive/21b
Also, there is something odd with `isKnownNonZero()`, if the non-zero
knowledge was specified as an assumption, it didn't pick it up (PR43267)
Reviewers: spatel, nikic, xbolva00
Reviewed By: spatel
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67411
llvm-svn: 371718
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 5e3a22ab..defa3c3 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1381,6 +1381,26 @@
return nullptr;
ICmpInst::Predicate UnsignedPred;
+
+ // Y = (A - B); Y >= A && Y != 0 --> Y >= A iff B != 0
+ // Y = (A - B); Y < A || Y == 0 --> Y < A iff B != 0
+ Value *A, *B;
+ if (match(Y, m_Sub(m_Value(A), m_Value(B))) &&
+ match(UnsignedICmp,
+ m_c_ICmp(UnsignedPred, m_Specific(Y), m_Specific(A)))) {
+ if (UnsignedICmp->getOperand(0) != Y)
+ UnsignedPred = ICmpInst::getSwappedPredicate(UnsignedPred);
+
+ if (UnsignedPred == ICmpInst::ICMP_UGE && IsAnd &&
+ EqPred == ICmpInst::ICMP_NE &&
+ isKnownNonZero(B, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
+ return UnsignedICmp;
+ if (UnsignedPred == ICmpInst::ICMP_ULT && !IsAnd &&
+ EqPred == ICmpInst::ICMP_EQ &&
+ isKnownNonZero(B, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
+ return UnsignedICmp;
+ }
+
if (match(UnsignedICmp, m_ICmp(UnsignedPred, m_Value(X), m_Specific(Y))) &&
ICmpInst::isUnsigned(UnsignedPred))
;