[InstSimplify] use any-zero matcher for fcmp folds
The m_APFloat matcher does not work with anything but strict
splat vector constants, so we could miss these folds and then
trigger an assertion in instcombine:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13201
The previous attempt at this in rL354406 had a logic bug that
actually triggered a regression test failure, but I failed to
notice it the first time.
llvm-svn: 354467
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 843b3e9..ed857dd 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3648,6 +3648,8 @@
}
// Handle fcmp with constant RHS.
+ // TODO: Use match with a specific FP value, so these work with vectors with
+ // undef lanes.
const APFloat *C;
if (match(RHS, m_APFloat(C))) {
// Check whether the constant is an infinity.
@@ -3676,28 +3678,7 @@
}
}
}
- if (C->isZero()) {
- switch (Pred) {
- case FCmpInst::FCMP_OGE:
- if (FMF.noNaNs() && CannotBeOrderedLessThanZero(LHS, Q.TLI))
- return getTrue(RetTy);
- break;
- case FCmpInst::FCMP_UGE:
- if (CannotBeOrderedLessThanZero(LHS, Q.TLI))
- return getTrue(RetTy);
- break;
- case FCmpInst::FCMP_ULT:
- if (FMF.noNaNs() && CannotBeOrderedLessThanZero(LHS, Q.TLI))
- return getFalse(RetTy);
- break;
- case FCmpInst::FCMP_OLT:
- if (CannotBeOrderedLessThanZero(LHS, Q.TLI))
- return getFalse(RetTy);
- break;
- default:
- break;
- }
- } else if (C->isNegative()) {
+ if (C->isNegative() && !C->isNegZero()) {
assert(!C->isNaN() && "Unexpected NaN constant!");
// TODO: We can catch more cases by using a range check rather than
// relying on CannotBeOrderedLessThanZero.
@@ -3721,6 +3702,28 @@
}
}
}
+ if (match(RHS, m_AnyZeroFP())) {
+ switch (Pred) {
+ case FCmpInst::FCMP_OGE:
+ if (FMF.noNaNs() && CannotBeOrderedLessThanZero(LHS, Q.TLI))
+ return getTrue(RetTy);
+ break;
+ case FCmpInst::FCMP_UGE:
+ if (CannotBeOrderedLessThanZero(LHS, Q.TLI))
+ return getTrue(RetTy);
+ break;
+ case FCmpInst::FCMP_ULT:
+ if (FMF.noNaNs() && CannotBeOrderedLessThanZero(LHS, Q.TLI))
+ return getFalse(RetTy);
+ break;
+ case FCmpInst::FCMP_OLT:
+ if (CannotBeOrderedLessThanZero(LHS, Q.TLI))
+ return getFalse(RetTy);
+ break;
+ default:
+ break;
+ }
+ }
// If the comparison is with the result of a select instruction, check whether
// comparing with either branch of the select always yields the same value.