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[SCEV] Make isImpliedCond smarter.

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Summary:
This change teaches isImpliedCond to infer things like "X sgt 0" => "X -
1 sgt -1".  The `ConstantRange` class has the logic to do the heavy
lifting, this change simply gets ScalarEvolution to exploit that when
reasonable.

Depends on D8345

Reviewers: atrick

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8346

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232576 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das
2015-03-18 00:41:29 +00:00
parent da5f3a3ca5
commit e027d74733
3 changed files with 83 additions and 0 deletions
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9
include/llvm/Analysis/ScalarEvolution.h
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@@ -535,6 +535,15 @@ namespace llvm {
const SCEV *FoundLHS,
const SCEV *FoundRHS);
/// isImpliedCondOperandsViaRanges - Test whether the condition described by
/// Pred, LHS, and RHS is true whenever the condition described by Pred,
/// FoundLHS, and FoundRHS is true. Utility function used by
/// isImpliedCondOperands.
bool isImpliedCondOperandsViaRanges(ICmpInst::Predicate Pred,
const SCEV *LHS, const SCEV *RHS,
const SCEV *FoundLHS,
const SCEV *FoundRHS);
/// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
/// in the header of its containing loop, we know the loop executes a
/// constant number of times, and the PHI node is just a recurrence