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| author | Sanjoy Das <sanjoy@playingwithpointers.com> | 2016-10-26 19:18:43 +0000 |
|---|---|---|
| committer | Sanjoy Das <sanjoy@playingwithpointers.com> | 2016-10-26 19:18:43 +0000 |
| commit | 01969218a4c33884460ac911cca3280bb184a344 (patch) | |
| tree | 924d68f86bef2386f8cfb243caf0d7ee4b42255f /llvm/lib/Analysis | |
| parent | 4447d7a8165fd5020f384341dd069a05b5206980 (diff) | |
| download | bcm5719-llvm-01969218a4c33884460ac911cca3280bb184a344.tar.gz bcm5719-llvm-01969218a4c33884460ac911cca3280bb184a344.zip | |
Simplify `x >=u x >> y` and `x >=u x udiv y`
Summary:
Extends InstSimplify to handle both `x >=u x >> y` and `x >=u x udiv y`.
This is a folloup of rL258422 and
https://github.com/rust-lang/rust/pull/30917 where llvm failed to
optimize away the bounds checking in a binary search.
Patch by Arthur Silva!
Reviewers: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D25941
llvm-svn: 285228
Diffstat (limited to 'llvm/lib/Analysis')
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index 1679d3a4667..398ac52c39c 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -2857,6 +2857,17 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, return getTrue(ITy); } + // x >=u x >> y + // x >=u x udiv y. + if (RBO && (match(RBO, m_LShr(m_Specific(LHS), m_Value())) || + match(RBO, m_UDiv(m_Specific(LHS), m_Value())))) { + // icmp pred X, (X op Y) + if (Pred == ICmpInst::ICMP_ULT) + return getFalse(ITy); + if (Pred == ICmpInst::ICMP_UGE) + return getTrue(ITy); + } + // handle: // CI2 << X == CI // CI2 << X != CI |
