[LV] Do not try to sink dead instructions.

Dead instructions do not need to be sunk. Currently we try and record
the recipies for them, but there are no recipes emitted for them and
there's nothing to sink. They can be removed from SinkAfter while
marking them for recording.

Fixes PR44634.

Reviewers: rengolin, hsaito, fhahn, Ayal, gilr

Reviewed By: gilr

Differential Revision: https://reviews.llvm.org/D73423

(cherry picked from commit a911fef3dd79e0a04b241be7b476dde7e99744c4)

2 files changed, 13 insertions, 8 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h b/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
index c3ca43fcd49..e5edd305d3d 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
@@ -279,9 +279,10 @@ private:
 
   /// Build a VPlan using VPRecipes according to the information gather by
   /// Legal. This method is only used for the legacy inner loop vectorizer.
-  VPlanPtr
-  buildVPlanWithVPRecipes(VFRange &Range, SmallPtrSetImpl<Value *> &NeedDef,
-                          SmallPtrSetImpl<Instruction *> &DeadInstructions);
+  VPlanPtr buildVPlanWithVPRecipes(
+      VFRange &Range, SmallPtrSetImpl<Value *> &NeedDef,
+      SmallPtrSetImpl<Instruction *> &DeadInstructions,
+      const DenseMap<Instruction *, Instruction *> &SinkAfter);
 
   /// Build VPlans for power-of-2 VF's between \p MinVF and \p MaxVF inclusive,
   /// according to the information gathered by Legal when it checked if it is
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 684a3098e56..c99b930a61f 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7118,25 +7118,29 @@ void LoopVectorizationPlanner::buildVPlansWithVPRecipes(unsigned MinVF,
   SmallPtrSet<Instruction *, 4> DeadInstructions;
   collectTriviallyDeadInstructions(DeadInstructions);
 
+  DenseMap<Instruction *, Instruction *> &SinkAfter = Legal->getSinkAfter();
+  // Dead instructions do not need sinking. Remove them from SinkAfter.
+  for (Instruction *I : DeadInstructions)
+    SinkAfter.erase(I);
+
   for (unsigned VF = MinVF; VF < MaxVF + 1;) {
     VFRange SubRange = {VF, MaxVF + 1};
-    VPlans.push_back(
-        buildVPlanWithVPRecipes(SubRange, NeedDef, DeadInstructions));
+    VPlans.push_back(buildVPlanWithVPRecipes(SubRange, NeedDef,
+                                             DeadInstructions, SinkAfter));
     VF = SubRange.End;
   }
 }
 
 VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
     VFRange &Range, SmallPtrSetImpl<Value *> &NeedDef,
-    SmallPtrSetImpl<Instruction *> &DeadInstructions) {
+    SmallPtrSetImpl<Instruction *> &DeadInstructions,
+    const DenseMap<Instruction *, Instruction *> &SinkAfter) {
 
   // Hold a mapping from predicated instructions to their recipes, in order to
   // fix their AlsoPack behavior if a user is determined to replicate and use a
   // scalar instead of vector value.
   DenseMap<Instruction *, VPReplicateRecipe *> PredInst2Recipe;
 
-  DenseMap<Instruction *, Instruction *> &SinkAfter = Legal->getSinkAfter();
-
   SmallPtrSet<const InterleaveGroup<Instruction> *, 1> InterleaveGroups;
 
   VPRecipeBuilder RecipeBuilder(OrigLoop, TLI, Legal, CM, Builder);