[llvm] [VPlan] Introduce CSE pass (PR #151872)

[Florian Hahn via llvm-commits]

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@@ -1772,6 +1772,93 @@ void VPlanTransforms::clearReductionWrapFlags(VPlan &Plan) {
   }
 }
 
+namespace {
+struct VPCSEDenseMapInfo : public DenseMapInfo<VPSingleDefRecipe *> {
+  static bool isSentinel(const VPSingleDefRecipe *Def) {
+    return Def == getEmptyKey() || Def == getTombstoneKey();
+  }
+
+  /// Get any instruction opcode or intrinsic ID data embedded in recipe \p R.
+  /// Returns an optional pair, where the first element indicates whether it is
+  /// an intrinsic ID.
+  static std::optional<std::pair<bool, unsigned>>
+  getOpcodeOrIntrinsicID(const VPRecipeBase &R) {
+    return TypeSwitch<const VPRecipeBase *,
+                      std::optional<std::pair<bool, unsigned>>>(&R)
+        .Case<VPInstruction, VPWidenRecipe, VPWidenCastRecipe,
+              VPWidenSelectRecipe, VPHistogramRecipe, VPPartialReductionRecipe,
+              VPReplicateRecipe>(
+            [](auto *I) { return std::make_pair(false, I->getOpcode()); })
+        .Case<VPWidenIntrinsicRecipe>([](auto *I) {
+          return std::make_pair(true, I->getVectorIntrinsicID());
+        })
+        .Default([](auto *) { return std::nullopt; });
+  }
+
+  static bool canHandle(const VPSingleDefRecipe *Def) {
+    return isa<VPInstruction, VPWidenRecipe, VPWidenCastRecipe,
+               VPWidenSelectRecipe, VPHistogramRecipe, VPReplicateRecipe,
+               VPWidenIntrinsicRecipe>(Def) &&
+           !Def->mayReadFromMemory();
+  }
+
+  /// Hash the underlying data of a VPSingleDefRecipe pointer, instead of
+  /// hashing the pointer itself.
+  static unsigned getHashValue(const VPSingleDefRecipe *Def) {
+    return hash_combine(Def->getVPDefID(), getOpcodeOrIntrinsicID(*Def),
+                        vputils::isSingleScalar(Def),
+                        hash_combine_range(Def->operands()));
+  }
+
+  static bool isEqual(const VPSingleDefRecipe *L, const VPSingleDefRecipe *R) {
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fhahn wrote:

This should probably be renamed, it may not return true for recipes with different result types. Or the type checking could be moved here.

https://github.com/llvm/llvm-project/pull/151872