[PATCH] D70125: [LV] PreferPredicateOverEpilog respecting predicate loop hint

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer created this revision.
SjoerdMeijer added reviewers: hsaito, samparker, dmgreen.
Herald added subscribers: rkruppe, hiraditya.
Herald added a project: LLVM.

The vectoriser queries TTI->preferPredicateOverEpilogue to determine whether tail-folding is preferred for a loop, but it was not respecting loop hint 'predicate' that can disable this, which has now been added. This showed that we were incorrectly initialising loop hint 'vectorize.predicate.enable' with 0 (i.e. FK_Disabled) but this should have been FK_Undefined, which has been fixed.


https://reviews.llvm.org/D70125

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/test/Transforms/LoopVectorize/ARM/prefer-tail-loop-folding.ll


Index: llvm/test/Transforms/LoopVectorize/ARM/prefer-tail-loop-folding.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/ARM/prefer-tail-loop-folding.ll
+++ llvm/test/Transforms/LoopVectorize/ARM/prefer-tail-loop-folding.ll
@@ -323,15 +323,12 @@
 }
 
 define void @pragma_vect_predicate_disable(i32* noalias nocapture %A, i32* noalias nocapture readonly %B, i32* noalias nocapture readonly %C) #0 {
-; CHECK-LABEL: pragma_vect_predicate_disable(
-;
-; FIXME:
-; respect loop hint predicate.enable = false, and don't tail-fold here:
-;
-; PREFER-FOLDING: call <4 x i32> @llvm.masked.load.v4i32.p0v4i32
-; PREFER-FOLDING: call <4 x i32> @llvm.masked.load.v4i32.p0v4i32
-; PREFER-FOLDING: call void @llvm.masked.store.v4i32.p0v4i32
-; PREFER-FOLDING: br i1 %{{.*}}, label %{{.*}}, label %vector.body
+; CHECK-LABEL:        pragma_vect_predicate_disable(
+; PREFER-FOLDING:     vector.body:
+; PREFER-FOLDING-NOT: call <4 x i32> @llvm.masked.load.v4i32.p0v4i32
+; PREFER-FOLDING-NOT: call <4 x i32> @llvm.masked.load.v4i32.p0v4i32
+; PREFER-FOLDING-NOT: call void @llvm.masked.store.v4i32.p0v4i32
+; PREFER-FOLDING:     br i1 %{{.*}}, label %{{.*}}, label %vector.body
 entry:
   br label %for.body
 
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7432,8 +7432,10 @@
       (F->hasOptSize() ||
        llvm::shouldOptimizeForSize(L->getHeader(), PSI, BFI)))
     SEL = CM_ScalarEpilogueNotAllowedOptSize;
-  else if (PreferPredicateOverEpilog || Hints.getPredicate() ||
-           TTI->preferPredicateOverEpilogue(L, LI, *SE, *AC, TLI, DT, LAI))
+  else if (PreferPredicateOverEpilog ||
+           Hints.getPredicate() == LoopVectorizeHints::FK_Enabled ||
+           (TTI->preferPredicateOverEpilogue(L, LI, *SE, *AC, TLI, DT, LAI) &&
+            Hints.getPredicate() != LoopVectorizeHints::FK_Disabled))
     SEL = CM_ScalarEpilogueNotNeededUsePredicate;
 
   return SEL;
Index: llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -72,7 +72,7 @@
       Interleave("interleave.count", InterleaveOnlyWhenForced, HK_UNROLL),
       Force("vectorize.enable", FK_Undefined, HK_FORCE),
       IsVectorized("isvectorized", 0, HK_ISVECTORIZED),
-      Predicate("vectorize.predicate.enable", 0, HK_PREDICATE), TheLoop(L),
+      Predicate("vectorize.predicate.enable", FK_Undefined, HK_PREDICATE), TheLoop(L),
       ORE(ORE) {
   // Populate values with existing loop metadata.
   getHintsFromMetadata();


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