[llvm] [VPlan] Add VPExpressionRecipe, replacing extended reduction recipes. (PR #144281)

[via llvm-commits]

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@@ -2563,30 +2563,182 @@ InstructionCost VPReductionRecipe::computeCost(ElementCount VF,
                                             Ctx.CostKind);
 }
 
-InstructionCost
-VPExtendedReductionRecipe::computeCost(ElementCount VF,
-                                       VPCostContext &Ctx) const {
-  unsigned Opcode = RecurrenceDescriptor::getOpcode(getRecurrenceKind());
+VPExpressionRecipe::VPExpressionRecipe(
+    ExpressionTypes ExpressionType,
+    ArrayRef<VPSingleDefRecipe *> ExpressionRecipes)
+    : VPSingleDefRecipe(VPDef::VPExpressionSC, {}, {}),
+      ExpressionRecipes(SetVector<VPSingleDefRecipe *>(
+                            ExpressionRecipes.begin(), ExpressionRecipes.end())
+                            .takeVector()),
+      ExpressionType(ExpressionType) {
+  assert(!ExpressionRecipes.empty() && "Nothing to combine?");
+  assert(
+      none_of(ExpressionRecipes,
+              [](VPSingleDefRecipe *R) { return R->mayHaveSideEffects(); }) &&
+      "expression cannot contain recipes with side-effects");
+
+  // Maintain a copy of the expression recipes as a set of users.
+  SmallPtrSet<VPUser *, 4> ExpressionRecipesAsSetOfUsers;
+  for (auto *R : ExpressionRecipes)
+    ExpressionRecipesAsSetOfUsers.insert(R);
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ayalz wrote:

Is this copy still needed, if VPExpressionRecipe holds its expression recipes in a SetVector?

https://github.com/llvm/llvm-project/pull/144281