[llvm-branch-commits] [llvm] [LV] Mask off possibly aliasing vector lanes (PR #100579)

[Sam Tebbs via llvm-branch-commits]

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@@ -3073,6 +3075,56 @@ struct VPWidenStoreEVLRecipe final : public VPWidenMemoryRecipe {
   }
 };
 
+// Given a pointer A that is being stored to, and pointer B that is being
+// read from, both with unknown lengths, create a mask that disables
+// elements which could overlap across a loop iteration. For example, if A
+// is X and B is X + 2 with VF being 4, only the final two elements of the
+// loaded vector can be stored since they don't overlap with the stored
+// vector. %b.vec = load %b ; = [s, t, u, v]
+// [...]
+// store %a, %b.vec ; only u and v can be stored as their addresses don't
+// overlap with %a + (VF - 1)
+class VPAliasLaneMaskRecipe : public VPSingleDefRecipe {
+
+public:
+  VPAliasLaneMaskRecipe(VPValue *Src, VPValue *Sink, unsigned ElementSize,
+                        bool WriteAfterRead)
+      : VPSingleDefRecipe(VPDef::VPAliasLaneMaskSC, {Src, Sink}),
+        ElementSize(ElementSize), WriteAfterRead(WriteAfterRead) {}
+
+  ~VPAliasLaneMaskRecipe() override = default;
+
+  VPAliasLaneMaskRecipe *clone() override {
+    return new VPAliasLaneMaskRecipe(getSourceValue(), getSinkValue(),
+                                     ElementSize, WriteAfterRead);
+  }
+
+  VP_CLASSOF_IMPL(VPDef::VPAliasLaneMaskSC);
+
+  void execute(VPTransformState &State) override;
+
+  /// Get the VPValue* for the pointer being read from
+  VPValue *getSourceValue() const { return getOperand(0); }
+
+  // Get the size of the element(s) accessed by the pointers
+  unsigned getAccessedElementSize() const { return ElementSize; }
+
+  /// Get the VPValue* for the pointer being stored to
+  VPValue *getSinkValue() const { return getOperand(1); }
+
+  bool isWriteAfterRead() const { return WriteAfterRead; }
+
+private:
+  unsigned ElementSize;
+  bool WriteAfterRead;
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+  /// Print the recipe.
+  void print(raw_ostream &O, const Twine &Indent,
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SamTebbs33 wrote:

Done.

https://github.com/llvm/llvm-project/pull/100579