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| author | Mehdi Amini <mehdi.amini@apple.com> | 2015-03-09 03:20:25 +0000 |
|---|---|---|
| committer | Mehdi Amini <mehdi.amini@apple.com> | 2015-03-09 03:20:25 +0000 |
| commit | eb242a504161f86f3a1e059732a0c4bf91c35735 (patch) | |
| tree | 5d0bbc099d952d01d41a31b9aebff8fdcd92125c /llvm/lib/Analysis | |
| parent | ce90329824037c89af64a5ee852e4c86f0c62cc7 (diff) | |
| download | bcm5719-llvm-eb242a504161f86f3a1e059732a0c4bf91c35735.tar.gz bcm5719-llvm-eb242a504161f86f3a1e059732a0c4bf91c35735.zip | |
InstCombine: fix fold "fcmp x, undef" to account for NaN
Summary:
See the two test cases.
; Can fold fcmp with undef on one side by choosing NaN for the undef
; Can fold fcmp with undef on both side
; fcmp u_pred undef, undef -> true
; fcmp o_pred undef, undef -> false
; because whatever you choose for the first undef
; you can choose NaN for the other undef
Reviewers: hfinkel, chandlerc, majnemer
Reviewed By: majnemer
Subscribers: majnemer, llvm-commits
Differential Revision: http://reviews.llvm.org/D7617
From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 231626
Diffstat (limited to 'llvm/lib/Analysis')
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index 0cb0982d311..d90f14a13fa 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -3054,8 +3054,13 @@ static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, if (Pred == FCmpInst::FCMP_TRUE) return ConstantInt::get(GetCompareTy(LHS), 1); - if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef - return UndefValue::get(GetCompareTy(LHS)); + // fcmp pred x, undef and fcmp pred undef, x + // fold to true if unordered, false if ordered + if (isa<UndefValue>(LHS) || isa<UndefValue>(RHS)) { + // Choosing NaN for the undef will always make unordered comparison succeed + // and ordered comparison fail. + return ConstantInt::get(GetCompareTy(LHS), CmpInst::isUnordered(Pred)); + } // fcmp x,x -> true/false. Not all compares are foldable. if (LHS == RHS) { |
