[llvm] a63eaa5 - [SLP] Avoid repeated visitation in getVectorElementSize(); NFC

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2020-03-22T14:34:29+01:00
New Revision: a63eaa5449fac237d492bd725a88fabf39881dc2

URL: https://github.com/llvm/llvm-project/commit/a63eaa5449fac237d492bd725a88fabf39881dc2
DIFF: https://github.com/llvm/llvm-project/commit/a63eaa5449fac237d492bd725a88fabf39881dc2.diff

LOG: [SLP] Avoid repeated visitation in getVectorElementSize(); NFC

We need to insert into the Visited set at the same time we insert
into the worklist. Otherwise we may end up pushing the same
instruction to the worklist multiple times, and only adding it to
the visited set later.

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 377aa78730b0..53678bc97d7e 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -5308,8 +5308,10 @@ unsigned BoUpSLP::getVectorElementSize(Value *V) const {
   // of memory operations where possible.
   SmallVector<Instruction *, 16> Worklist;
   SmallPtrSet<Instruction *, 16> Visited;
-  if (auto *I = dyn_cast<Instruction>(V))
+  if (auto *I = dyn_cast<Instruction>(V)) {
     Worklist.push_back(I);
+    Visited.insert(I);
+  }
 
   // Traverse the expression tree in bottom-up order looking for loads. If we
   // encounter an instruction we don't yet handle, we give up.
@@ -5317,7 +5319,6 @@ unsigned BoUpSLP::getVectorElementSize(Value *V) const {
   auto FoundUnknownInst = false;
   while (!Worklist.empty() && !FoundUnknownInst) {
     auto *I = Worklist.pop_back_val();
-    Visited.insert(I);
 
     // We should only be looking at scalar instructions here. If the current
     // instruction has a vector type, give up.
@@ -5337,7 +5338,7 @@ unsigned BoUpSLP::getVectorElementSize(Value *V) const {
              isa<CmpInst>(I) || isa<SelectInst>(I) || isa<BinaryOperator>(I)) {
       for (Use &U : I->operands())
         if (auto *J = dyn_cast<Instruction>(U.get()))
-          if (!Visited.count(J))
+          if (Visited.insert(J).second)
             Worklist.push_back(J);
     }