[llvm] 7b9f988 - [VPlan] Limit stride replacement to vector region and middle VPBB (NFC).

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2024-10-24T15:08:36-07:00
New Revision: 7b9f988a535c3549b71025e951e3a36a2bf0fa03

URL: https://github.com/llvm/llvm-project/commit/7b9f988a535c3549b71025e951e3a36a2bf0fa03
DIFF: https://github.com/llvm/llvm-project/commit/7b9f988a535c3549b71025e951e3a36a2bf0fa03.diff

LOG: [VPlan] Limit stride replacement to vector region and middle VPBB (NFC).

At the moment this in NFC, but ensures we only replace uses that are
dominated by runtime checks as we model more of the skeleton in VPlan.

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 60a94ca1f86e42..e1173ddd71af9c 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -9189,6 +9189,14 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
 
   // Replace VPValues for known constant strides guaranteed by predicate scalar
   // evolution.
+  auto CanUseVersionedStride = [&Plan](VPUser &U, unsigned) {
+    auto *R = dyn_cast<VPRecipeBase>(&U);
+    if (!R)
+      return false;
+    return R->getParent()->getParent() ||
+           R->getParent() ==
+               Plan->getVectorLoopRegion()->getSinglePredecessor();
+  };
   for (auto [_, Stride] : Legal->getLAI()->getSymbolicStrides()) {
     auto *StrideV = cast<SCEVUnknown>(Stride)->getValue();
     auto *ScevStride = dyn_cast<SCEVConstant>(PSE.getSCEV(StrideV));
@@ -9199,7 +9207,7 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
     auto *CI = Plan->getOrAddLiveIn(
         ConstantInt::get(Stride->getType(), ScevStride->getAPInt()));
     if (VPValue *StrideVPV = Plan->getLiveIn(StrideV))
-      StrideVPV->replaceAllUsesWith(CI);
+      StrideVPV->replaceUsesWithIf(CI, CanUseVersionedStride);
 
     // The versioned value may not be used in the loop directly but through a
     // sext/zext. Add new live-ins in those cases.
@@ -9213,7 +9221,7 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
       APInt C = isa<SExtInst>(U) ? ScevStride->getAPInt().sext(BW)
                                  : ScevStride->getAPInt().zext(BW);
       VPValue *CI = Plan->getOrAddLiveIn(ConstantInt::get(U->getType(), C));
-      StrideVPV->replaceAllUsesWith(CI);
+      StrideVPV->replaceUsesWithIf(CI, CanUseVersionedStride);
     }
   }