[llvm] Expanding the Histogram Intrinsic (PR #127399)

[Graham Hunter via llvm-commits]

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@@ -1277,24 +1278,51 @@ InstructionCost VPHistogramRecipe::computeCost(ElementCount VF,
   IntrinsicCostAttributes ICA(Intrinsic::experimental_vector_histogram_add,
                               Type::getVoidTy(Ctx.LLVMCtx),
                               {PtrTy, IncTy, MaskTy});
+  auto *UpdateInst = getOperand(2)->getUnderlyingValue();
+  InstructionCost UpdateCost;
+  if (isa<IntrinsicInst>(UpdateInst)) {
+    IntrinsicCostAttributes UpdateICA(Opcode, IncTy, {IncTy, IncTy});
+    UpdateCost = Ctx.TTI.getIntrinsicInstrCost(UpdateICA, Ctx.CostKind);
+  } else
+    UpdateCost = Ctx.TTI.getArithmeticInstrCost(Opcode, VTy, Ctx.CostKind);
 
   // Add the costs together with the add/sub operation.
   return Ctx.TTI.getIntrinsicInstrCost(ICA, Ctx.CostKind) + MulCost +
-         Ctx.TTI.getArithmeticInstrCost(Opcode, VTy, Ctx.CostKind);
+         UpdateCost;
 }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void VPHistogramRecipe::print(raw_ostream &O, const Twine &Indent,
                               VPSlotTracker &SlotTracker) const {
+  auto *UpdateInst = cast<Instruction>(getOperand(2)->getUnderlyingValue());
+  assert(isLegalUpdateInstruction(UpdateInst) &&
+         "Found Ilegal update instruction for histogram");
   O << Indent << "WIDEN-HISTOGRAM buckets: ";
   getOperand(0)->printAsOperand(O, SlotTracker);
 
-  if (Opcode == Instruction::Sub)
-    O << ", dec: ";
-  else {
-    assert(Opcode == Instruction::Add);
-    O << ", inc: ";
+  std::string UpdateMsg;
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huntergr-arm wrote:

No need for the temporary I think, you can just use `O << ", <update>: ";`

https://github.com/llvm/llvm-project/pull/127399