[llvm-branch-commits] [clang] [llvm] [HLSL][RootSignature] Add Metadata generation of Root Signatures for Attr (PR #125131)

[Finn Plummer via llvm-branch-commits]

================
@@ -0,0 +1,108 @@
+//===- HLSLRootSignature.cpp - HLSL Root Signature helper objects
+//----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file This file contains helpers for working with HLSL Root Signatures.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Frontend/HLSL/HLSLRootSignature.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/Module.h"
+
+namespace llvm {
+namespace hlsl {
+namespace rootsig {
+
+// Static helper functions
+
+static MDString *ClauseTypeToName(LLVMContext &Ctx, ClauseType Type) {
+  StringRef Name;
+  switch (Type) {
+  case ClauseType::CBuffer:
+    Name = "CBV";
+    break;
+  case ClauseType::SRV:
+    Name = "SRV";
+    break;
+  case ClauseType::UAV:
+    Name = "UAV";
+    break;
+  case ClauseType::Sampler:
+    Name = "Sampler";
+    break;
+  }
+  return MDString::get(Ctx, Name);
+}
+
+// Helper struct so that we can use the overloaded notation of std::visit
+template <class... Ts> struct OverloadBuilds : Ts... {
+  using Ts::operator()...;
+};
+template <class... Ts> OverloadBuilds(Ts...) -> OverloadBuilds<Ts...>;
+
+MDNode *MetadataBuilder::BuildRootSignature() {
+  for (const RootElement &Element : Elements) {
+    MDNode *ElementMD =
+        std::visit(OverloadBuilds{
+                       [&](DescriptorTable Table) -> MDNode * {
+                         return BuildDescriptorTable(Table);
+                       },
+                       [&](DescriptorTableClause Clause) -> MDNode * {
+                         return BuildDescriptorTableClause(Clause);
+                       },
+                   },
+                   Element);
+    GeneratedMetadata.push_back(ElementMD);
+  }
+
+  return MDNode::get(Ctx, GeneratedMetadata);
+}
+
+MDNode *MetadataBuilder::BuildDescriptorTable(const DescriptorTable &Table) {
+  IRBuilder<> B(Ctx);
+  SmallVector<Metadata *> TableOperands;
+  // Set the mandatory arguments
+  TableOperands.push_back(MDString::get(Ctx, "DescriptorTable"));
+  TableOperands.push_back(ConstantAsMetadata::get(
+      B.getInt32(llvm::to_underlying(Table.Visibility))));
+
+  // Remaining operands are references to the table's clauses. The in-memory
+  // representation of the Root Elements created from parsing will ensure that
+  // the previous N elements are the clauses for this table.
+  assert(Table.NumClauses <= GeneratedMetadata.size() &&
+         "Table expected all owned clauses to be generated already");
+  // So, add a refence to each clause to our operands
+  TableOperands.append(GeneratedMetadata.end() - Table.NumClauses,
+                       GeneratedMetadata.end());
+  // Then, remove those clauses from the general list of Root Elements
+  GeneratedMetadata.pop_back_n(Table.NumClauses);
+
+  return MDNode::get(Ctx, TableOperands);
+}
+
+MDNode *MetadataBuilder::BuildDescriptorTableClause(
+    const DescriptorTableClause &Clause) {
+  IRBuilder<> B(Ctx);
+  return MDNode::get(
+      Ctx, {
+               ClauseTypeToName(Ctx, Clause.Type),
+               ConstantAsMetadata::get(B.getInt32(Clause.NumDescriptors)),
+               ConstantAsMetadata::get(B.getInt32(Clause.Register.Number)),
+               ConstantAsMetadata::get(B.getInt32(Clause.Space)),
+               ConstantAsMetadata::get(
----------------
inbelic wrote:

Good catch. I think the specification is wrong then? Based on https://learn.microsoft.com/en-us/windows/win32/api/d3d12/ns-d3d12-d3d12_descriptor_range?redirectedfrom=MSDN we should need to pass that down.

I will raise this

https://github.com/llvm/llvm-project/pull/125131