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

[Gaëtan Bossu via llvm-commits]

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@@ -19945,6 +19945,46 @@ static bool checkTreeSizes(ArrayRef<std::pair<unsigned, unsigned>> Sizes,
   return Dev * 96 / (Mean * Mean) == 0;
 }
 
+namespace {
+
+/// A reference to a store instruction and the distance of its address to a base
+/// pointer.
+struct InstAndPtrDist {
+  InstAndPtrDist(unsigned InstrIdx, int DistToBasePtr)
+      : InstrIdx(InstrIdx), DistToBasePtr(DistToBasePtr) {}
+  unsigned InstrIdx;
+  int DistToBasePtr;
+};
+struct PtrDistCompare {
+  bool operator()(const InstAndPtrDist &Op1, const InstAndPtrDist &Op2) const {
+    return Op1.DistToBasePtr < Op2.DistToBasePtr;
+  }
+};
+
+/// A group of instructions that we'll try to bundle together using vector ops.
+/// They are ordered using the signed distance of their address operand to the
+/// address of this group's BaseInstr.
+struct RelatedStoreInsts {
+  RelatedStoreInsts(unsigned BaseInstrIdx) { reset(BaseInstrIdx); }
+  void reset(unsigned NewBaseInstr) {
+    BaseInstrIdx = NewBaseInstr;
+    Instrs.clear();
+    Instrs.emplace(NewBaseInstr, 0);
+  }
+
+  // Note: PtrDistCompare ensures that there a 1:1 mapping between distance and
+  // instruction. This could be turned into a map to be more obvious.
+  using InstSet = std::set<InstAndPtrDist, PtrDistCompare>;
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gbossu wrote:

As far as I know, DenseMap is unordered, and we do rely on the iteration order being "sorted". I guess I'll stick to `std::map` then. It's also fine to me if we leave the patch at it is, with the `std::set`. I can do the change to `std::map` in a follow-up if you prefer.

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