[PATCH] D72324: [LV] Still vectorise when tail-folding can't find a primary inducation variable

[Sam Parker via Phabricator via llvm-commits]

samparker accepted this revision.
samparker added a comment.
This revision is now accepted and ready to land.

LGTM



================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:7538
+                                        LVL.getLAI()) &&
+       Hints.getPredicate() != LoopVectorizeHints::FK_Disabled))
+    return CM_ScalarEpilogueNotNeededUsePredicate;
----------------
SjoerdMeijer wrote:
> samparker wrote:
> > If a hint is provided to disable folding, then we shouldn't even look at any of the Prefer stuff, right? So PredicateOptDisabled = (PreferPredicateOverEpilog.getNumOccurrences() && !PreferPredicateOverEpilog) || Hints.getPredicate() == LoopVectorizeHints::FK_Disabled)
> We have these test cases:
> 
>   Transforms/LoopVectorize/ARM/tail-loop-folding.ll
>   Transforms/LoopVectorize/X86/tail_loop_folding.ll
> 
> That have functions with loop hint `predicate.enable=false` and also option `-prefer-predicate-over-epilog` set. The expected output (in these tests) is that this will enable predication, and thus the option overrides the loop hint. That's why I didn't move the loophint check to `PredicateOptDisabled`.
Bah, I've missed some brackets - sorry!


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  https://reviews.llvm.org/D72324/new/

https://reviews.llvm.org/D72324