forked from OSchip/llvm-project
099eca832e
At the moment, LoopPredication completely bails out if it sees a latch of the form: %cmp = icmp ne %iv, %N br i1 %cmp, label %loop, label %exit OR %cmp = icmp ne %iv.next, %NPlus1 br i1 %cmp, label %loop, label %exit This is unfortunate since this is exactly the form that LFTR likes to produce. So, go ahead and recognize simple cases where we can. For pre-increment loops, we leverage the fact that LFTR likes canonical counters (i.e. those starting at zero) and a (presumed) range fact on RHS to discharge the check trivially. For post-increment forms, the key insight is in remembering that LFTR had to insert a (N+1) for the RHS. CVP can hopefully prove that add nsw/nuw (if there's appropriate range on N to start with). This leaves us both with the post-inc IV and the RHS involving an nsw/nuw add, and SCEV can discharge that with no problem. This does still need to be extended to handle non-one steps, or other harder patterns of variable (but range restricted) starting values. That'll come later. Differential Revision: https://reviews.llvm.org/D62748 llvm-svn: 362282 |
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| .. | ||
| basic.ll | ||
| basic_widenable_branch_guards.ll | ||
| invariant_load.ll | ||
| nested.ll | ||
| profitability.ll | ||
| reverse.ll | ||
| visited.ll | ||
| widened.ll | ||