[llvm] [SLP] Use named structs in vectorizeStores() (NFC) (PR #132781)

[Gaëtan Bossu via llvm-commits]

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@@ -19923,31 +19923,51 @@ bool SLPVectorizerPass::vectorizeStores(
   BoUpSLP::ValueSet VectorizedStores;
   bool Changed = false;
 
+  /// A store instruction and the distance of its address to a base pointer.
+  struct CandidateInstr {
+    CandidateInstr(unsigned InstrIdx, int DistToBasePtr)
+        : InstrIdx(InstrIdx), DistToBasePtr(DistToBasePtr) {}
+    unsigned InstrIdx;
+    int DistToBasePtr;
+  };
   struct StoreDistCompare {
-    bool operator()(const std::pair<unsigned, int> &Op1,
-                    const std::pair<unsigned, int> &Op2) const {
-      return Op1.second < Op2.second;
+    bool operator()(const CandidateInstr &Op1,
+                    const CandidateInstr &Op2) const {
+      return Op1.DistToBasePtr < Op2.DistToBasePtr;
     }
   };
-  // A set of pairs (index of store in Stores array ref, Distance of the store
-  // address relative to base store address in units).
-  using StoreIndexToDistSet =
-      std::set<std::pair<unsigned, int>, StoreDistCompare>;
-  auto TryToVectorize = [&](const StoreIndexToDistSet &Set) {
+
+  /// A group of store instructions that we'll try to bundle together.
+  /// They are ordered using their signed distance to the address of this
+  /// set's BaseInstr.
+  struct CandidateBundle {
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gbossu wrote:

> `Bundle` is reserved for scheduling model
Agree, I think it's better not to use it. That actually did confuse me when I first saw this word in the SLPVectorizer 😅 I'd still prefer to use a word that describes the intent rather than a word that just gives an implementation detail. What would you think about `ComparableStores`? Reading through the code, I think this is what we use the data structure for: it collects all pointers based off of a same base, and tries to splice that list to create vector ops.

> Also, better to move these structs out of function into the anonymous namespace
Agree again, I just assumed you'd prefer it this way because you seem to prefer lambdas over free functions. I will move the declarations out 🙂 

https://github.com/llvm/llvm-project/pull/132781