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

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer marked an inline comment as done.
SjoerdMeijer added inline comments.


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Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:7538
+                                        LVL.getLAI()) &&
+       Hints.getPredicate() != LoopVectorizeHints::FK_Disabled))
+    return CM_ScalarEpilogueNotNeededUsePredicate;
----------------
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`.


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

https://reviews.llvm.org/D72324