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9d55b40815
Summary:
This implements a new method of run-time checking the NoWrap
SCEV predicates, which should be easier to optimize and nicer
for targets that don't correctly handle multiplication/addition
of large integer types (like i128).
If the AddRec is {a,+,b} and the backedge taken count is c,
the idea is to check that |b| * c doesn't have unsigned overflow,
and depending on the sign of b, that:
a + |b| * c >= a (b >= 0) or
a - |b| * c <= a (b <= 0)
where the comparisons above are signed or unsigned, depending on
the flag that we're checking.
The advantage of doing this is that we avoid extending to a larger
type and we avoid the multiplication of large types (multiplying
i128 can be expensive).
Reviewers: sanjoy
Subscribers: llvm-commits, mzolotukhin
Differential Revision: http://reviews.llvm.org/D19266
llvm-svn: 267389
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| .. | ||
| AssumptionCache | ||
| BasicAA | ||
| BlockFrequencyInfo | ||
| BranchProbabilityInfo | ||
| CallGraph | ||
| CFLAliasAnalysis | ||
| CostModel | ||
| Delinearization | ||
| DemandedBits | ||
| DependenceAnalysis | ||
| DivergenceAnalysis | ||
| DominanceFrontier | ||
| Dominators | ||
| GlobalsModRef | ||
| LazyCallGraph | ||
| Lint | ||
| LoopAccessAnalysis | ||
| LoopInfo | ||
| MemoryDependenceAnalysis | ||
| PostDominators | ||
| RegionInfo | ||
| ScalarEvolution | ||
| ScopedNoAliasAA | ||
| TypeBasedAliasAnalysis | ||
| ValueTracking | ||
| alias-analysis-uses.ll | ||