[LV] Hoist code to mark conditional assumes as dead to caller (NFC).

fhahn · fhahn · commit d1f849a284d9 · 2020-01-28T08:50:44.000-08:00
This is a follow-up suggested in D73423. It is sufficient to just add
the conditional assumes to DeadInstructions once.
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7130,6 +7130,13 @@ void LoopVectorizationPlanner::buildVPlansWithVPRecipes(unsigned MinVF,
   SmallPtrSet<Instruction *, 4> DeadInstructions;
   collectTriviallyDeadInstructions(DeadInstructions);
 
+  // Add assume instructions we need to drop to DeadInstructions, to prevent
+  // them from being added to the VPlan.
+  // TODO: We only need to drop assumes in blocks that get flattend. If the
+  // control flow is preserved, we should keep them.
+  auto &ConditionalAssumes = Legal->getConditionalAssumes();
+  DeadInstructions.insert(ConditionalAssumes.begin(), ConditionalAssumes.end());
+
   DenseMap<Instruction *, Instruction *> &SinkAfter = Legal->getSinkAfter();
   // Dead instructions do not need sinking. Remove them from SinkAfter.
   for (Instruction *I : DeadInstructions)
@@ -7192,13 +7199,6 @@ VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
   // visit each basic block after having visited its predecessor basic blocks.
   // ---------------------------------------------------------------------------
 
-  // Add assume instructions we need to drop to DeadInstructions, to prevent
-  // them from being added to the VPlan.
-  // TODO: We only need to drop assumes in blocks that get flattend. If the
-  // control flow is preserved, we should keep them.
-  auto &ConditionalAssumes = Legal->getConditionalAssumes();
-  DeadInstructions.insert(ConditionalAssumes.begin(), ConditionalAssumes.end());
-
   // Create a dummy pre-entry VPBasicBlock to start building the VPlan.
   VPBasicBlock *VPBB = new VPBasicBlock("Pre-Entry");
   auto Plan = std::make_unique<VPlan>(VPBB);
