[llvm] [LV][VPlan] Add initial support for CSA vectorization (PR #121222)

[Florian Hahn via llvm-commits]

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@@ -2565,6 +2600,136 @@ class VPBranchOnMaskRecipe : public VPRecipeBase {
   }
 };
 
+class VPConditionalScalarAssignmentHeaderPHIRecipe final
+    : public VPHeaderPHIRecipe {
+public:
+  VPConditionalScalarAssignmentHeaderPHIRecipe(PHINode *Phi,
+                                               VPValue &VPInitData)
+      : VPHeaderPHIRecipe(VPDef::VPConditionalScalarAssignmentHeaderPHISC, Phi,
+                          &VPInitData) {}
+
+  ~VPConditionalScalarAssignmentHeaderPHIRecipe() override = default;
+
+  VPConditionalScalarAssignmentHeaderPHIRecipe *clone() override {
+    return new VPConditionalScalarAssignmentHeaderPHIRecipe(
+        cast<PHINode>(getUnderlyingInstr()), *getOperand(0));
+  }
+
+  VPValue *NewData = nullptr;
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fhahn wrote:

In general, recipes should manage any VPValues via their operands; otherwise `replaceAllUsesWith` won't work as expected.

https://github.com/llvm/llvm-project/pull/121222