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| author | David Majnemer <david.majnemer@gmail.com> | 2014-05-14 20:16:28 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-05-14 20:16:28 +0000 |
| commit | cd237ed5853bda1dab27323236119e4342a19860 (patch) | |
| tree | ae30d37e6dbf9018ec09943c2628b04a3c861973 /lib/Analysis | |
| parent | e0776de2df9c47af5002cbc04354b52f3a1ee9b3 (diff) | |
| download | llvm-cd237ed5853bda1dab27323236119e4342a19860.tar.gz llvm-cd237ed5853bda1dab27323236119e4342a19860.tar.bz2 llvm-cd237ed5853bda1dab27323236119e4342a19860.tar.xz | |
InstSimplify: Optimize signed icmp of -(zext V)
Summary:
We know that -(zext V) will always be <= zero, simplify signed icmps
that have these.
Uncovered using http://www.cs.utah.edu/~regehr/souper/
Reviewers: nicholas
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D3754
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208809 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Analysis')
| -rw-r--r-- | lib/Analysis/InstructionSimplify.cpp | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp index 4c621b0e91..5421a39922 100644 --- a/lib/Analysis/InstructionSimplify.cpp +++ b/lib/Analysis/InstructionSimplify.cpp @@ -2280,6 +2280,28 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, } } + // 0 - (zext X) pred C + if (!CmpInst::isUnsigned(Pred) && match(LHS, m_Neg(m_ZExt(m_Value())))) { + if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) { + if (RHSC->getValue().isStrictlyPositive()) { + if (Pred == ICmpInst::ICMP_SLT) + return ConstantInt::getTrue(RHSC->getContext()); + if (Pred == ICmpInst::ICMP_SGE) + return ConstantInt::getFalse(RHSC->getContext()); + if (Pred == ICmpInst::ICMP_EQ) + return ConstantInt::getFalse(RHSC->getContext()); + if (Pred == ICmpInst::ICMP_NE) + return ConstantInt::getTrue(RHSC->getContext()); + } + if (RHSC->getValue().isNonNegative()) { + if (Pred == ICmpInst::ICMP_SLE) + return ConstantInt::getTrue(RHSC->getContext()); + if (Pred == ICmpInst::ICMP_SGT) + return ConstantInt::getFalse(RHSC->getContext()); + } + } + } + // icmp pred (urem X, Y), Y if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) { bool KnownNonNegative, KnownNegative; |