[clang-tools-extra] [llvm] [clang] [VPlan] Add new VPUniformPerUFRecipe, use for step truncation. (PR #78113)

[via cfe-commits]

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@@ -1469,6 +1465,47 @@ void VPReplicateRecipe::print(raw_ostream &O, const Twine &Indent,
 }
 #endif
 
+Value *VPScalarCastRecipe ::generate(VPTransformState &State, unsigned Part) {
+  assert(vputils::onlyFirstLaneUsed(this) &&
+         "Codegen only implemented for first lane only.");
+  switch (Opcode) {
+  case Instruction::SExt:
+  case Instruction::ZExt:
+  case Instruction::Trunc: {
+    Value *Op = State.get(getOperand(0), VPIteration(Part, 0));
+    return State.Builder.CreateCast(Instruction::CastOps(Opcode), Op, ResultTy);
+  }
+  default:
+    llvm_unreachable("opcode not implemented yet");
+  }
+}
+
+void VPScalarCastRecipe ::execute(VPTransformState &State) {
+  bool UniformAcrossUFs = all_of(operands(), [](VPValue *Op) {
+    return Op->isDefinedOutsideVectorRegions();
+  });
+  for (unsigned Part = 0; Part != State.UF; ++Part) {
+    Value *Res;
+    // Only generate a single instance, if the recipe is uniform across all UFs.
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ayalz wrote:

Only a single instance is going to be generated, in the preheader? Recipe is uniform across all UFs by (current) definition (and even more so - invariant). Can assert UniformAcrossUFs holds, along with onlyFirstLaneUsed.

https://github.com/llvm/llvm-project/pull/78113