[PATCH] D85784: [PGO][PGSO][LV] Fix loop not vectorized issue under profile guided size opts.

[Hiroshi Yamauchi via Phabricator via llvm-commits]

yamauchi created this revision.
yamauchi added reviewers: davidxl, Ayal.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.
yamauchi requested review of this revision.

D81345 <https://reviews.llvm.org/D81345> appears to accidentally disables vectorization when explicitly
enabled. As PGSO isn't currently accessible from LoopAccessInfo, revert back to
the vectorization with versioning-for-unit-stride for PGSO.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D85784

Files:
  llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
  llvm/test/Transforms/LoopVectorize/optsize.ll


Index: llvm/test/Transforms/LoopVectorize/optsize.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/optsize.ll
+++ llvm/test/Transforms/LoopVectorize/optsize.ll
@@ -284,6 +284,34 @@
   ret void
 }
 
+; Vectorize with versioning for unit stride for PGSO and enabled vectorization.
+;
+define void @stride1_pgso(i16* noalias %B, i32 %BStride) !prof !14 {
+; CHECK-LABEL: @stride1_pgso(
+; CHECK: vector.body
+;
+; PGSO-LABEL: @stride1_pgso(
+; PGSO: vector.body
+;
+; NPGSO-LABEL: @stride1_pgso(
+; NPGSO: vector.body
+
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i32 [ %iv.next, %for.body ], [ 0, %entry ]
+  %mulB = mul nsw i32 %iv, %BStride
+  %gepOfB = getelementptr inbounds i16, i16* %B, i32 %mulB
+  store i16 42, i16* %gepOfB, align 4
+  %iv.next = add nuw nsw i32 %iv, 1
+  %exitcond = icmp eq i32 %iv.next, 1025
+  br i1 %exitcond, label %for.end, label %for.body, !llvm.loop !15
+
+for.end:
+  ret void
+}
+
 ; PR46652: Check that the need for stride==1 check prevents vectorizing a loop
 ; having tiny trip count, when compiling w/o -Os/-Oz.
 ; CHECK-LABEL: @pr46652
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2822,7 +2822,8 @@
       return;
 
   assert(!(SCEVCheckBlock->getParent()->hasOptSize() ||
-           OptForSizeBasedOnProfile) &&
+           (OptForSizeBasedOnProfile &&
+            Cost->Hints->getForce() != LoopVectorizeHints::FK_Enabled)) &&
          "Cannot SCEV check stride or overflow when optimizing for size");
 
   SCEVCheckBlock->setName("vector.scevcheck");
@@ -7913,12 +7914,17 @@
     BlockFrequencyInfo *BFI, TargetTransformInfo *TTI, TargetLibraryInfo *TLI,
     AssumptionCache *AC, LoopInfo *LI, ScalarEvolution *SE, DominatorTree *DT,
     LoopVectorizationLegality &LVL) {
-  bool OptSize =
-      F->hasOptSize() || llvm::shouldOptimizeForSize(L->getHeader(), PSI, BFI,
-                                                     PGSOQueryType::IRPass);
   // 1) OptSize takes precedence over all other options, i.e. if this is set,
   // don't look at hints or options, and don't request a scalar epilogue.
-  if (OptSize)
+  // (For PGSO, as shouldOptimizeForSize isn't currently accessible from
+  // LoopAccessInfo (due to code dependency and not being able to reliably get
+  // PSI/BFI from a loop analysis under NPM), we cannot suppress the collection
+  // of strides in LoopAccessInfo::analyzeLoop() and vectorize without
+  // versioning when the vectorization is forced, unlike hasOptSize. So revert
+  // back to the old way and vectorize with versioning when forced. See D81345.)
+  if (F->hasOptSize() || (llvm::shouldOptimizeForSize(L->getHeader(), PSI, BFI,
+                                                      PGSOQueryType::IRPass) &&
+                          Hints.getForce() != LoopVectorizeHints::FK_Enabled))
     return CM_ScalarEpilogueNotAllowedOptSize;
 
   bool PredicateOptDisabled = PreferPredicateOverEpilog.getNumOccurrences() &&


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