[llvm] 1a54889 - [LV] Ensure WidenCanonicalIVRecipe is always created in header (NFC).

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2021-12-21T15:14:48Z
New Revision: 1a54889f48faceb931e2ead76cfb78e43191b297

URL: https://github.com/llvm/llvm-project/commit/1a54889f48faceb931e2ead76cfb78e43191b297
DIFF: https://github.com/llvm/llvm-project/commit/1a54889f48faceb931e2ead76cfb78e43191b297.diff

LOG: [LV] Ensure WidenCanonicalIVRecipe is always created in header (NFC).

The VPWidenCanonicalIVRecipe must always be created in the phi section
of the header block. Use that block as insert point.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index a85ec01d778da..ec95cd62ed268 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -8446,11 +8446,6 @@ VPValue *VPRecipeBuilder::createBlockInMask(BasicBlock *BB, VPlanPtr &Plan) {
     if (!CM.blockNeedsPredicationForAnyReason(BB))
       return BlockMaskCache[BB] = BlockMask; // Loop incoming mask is all-one.
 
-    // Create the block in mask as the first non-phi instruction in the block.
-    VPBuilder::InsertPointGuard Guard(Builder);
-    auto NewInsertionPoint = Builder.getInsertBlock()->getFirstNonPhi();
-    Builder.setInsertPoint(Builder.getInsertBlock(), NewInsertionPoint);
-
     // Introduce the early-exit compare IV <= BTC to form header block mask.
     // This is used instead of IV < TC because TC may wrap, unlike BTC.
     // Start by constructing the desired canonical IV.
@@ -8458,10 +8453,17 @@ VPValue *VPRecipeBuilder::createBlockInMask(BasicBlock *BB, VPlanPtr &Plan) {
     if (Legal->getPrimaryInduction())
       IV = Plan->getOrAddVPValue(Legal->getPrimaryInduction());
     else {
+      VPBasicBlock *HeaderVPBB = Plan->getEntry()->getEntryBasicBlock();
       auto *IVRecipe = new VPWidenCanonicalIVRecipe();
-      Builder.getInsertBlock()->insert(IVRecipe, NewInsertionPoint);
+      HeaderVPBB->insert(IVRecipe, HeaderVPBB->getFirstNonPhi());
       IV = IVRecipe;
     }
+
+    // Create the block in mask as the first non-phi instruction in the block.
+    VPBuilder::InsertPointGuard Guard(Builder);
+    auto NewInsertionPoint = Builder.getInsertBlock()->getFirstNonPhi();
+    Builder.setInsertPoint(Builder.getInsertBlock(), NewInsertionPoint);
+
     VPValue *BTC = Plan->getOrCreateBackedgeTakenCount();
     bool TailFolded = !CM.isScalarEpilogueAllowed();