[llvm-branch-commits] [clang] [llvm] [HLSL][RootSignature] Add Metadata generation of Root Signatures for Attr (PR #125131)
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Wed Feb 12 16:23:01 PST 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-codegen
Author: Finn Plummer (inbelic)
<details>
<summary>Changes</summary>
- Define and implement `MetadataBuilder` in `HLSLRootSignature`
- Integrate and invoke the builder in `CGHLSLRuntime.cpp` to generate the Root Signature for any associated entry functions
- Add tests to demonstrate functionality in `RootSignature.hlsl`
Resolves https://github.com/llvm/llvm-project/issues/126584
---
Full diff: https://github.com/llvm/llvm-project/pull/125131.diff
5 Files Affected:
- (modified) clang/lib/CodeGen/CGHLSLRuntime.cpp (+20)
- (added) clang/test/CodeGenHLSL/RootSignature.hlsl (+29)
- (modified) llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h (+27)
- (modified) llvm/lib/Frontend/HLSL/CMakeLists.txt (+1)
- (added) llvm/lib/Frontend/HLSL/HLSLRootSignature.cpp (+108)
``````````diff
diff --git a/clang/lib/CodeGen/CGHLSLRuntime.cpp b/clang/lib/CodeGen/CGHLSLRuntime.cpp
index c354e58e15f4b..62d062be91046 100644
--- a/clang/lib/CodeGen/CGHLSLRuntime.cpp
+++ b/clang/lib/CodeGen/CGHLSLRuntime.cpp
@@ -119,6 +119,20 @@ GlobalVariable *replaceBuffer(CGHLSLRuntime::Buffer &Buf) {
return CBGV;
}
+void addRootSignature(ArrayRef<llvm::hlsl::rootsig::RootElement> Elements,
+ llvm::Function *Fn, llvm::Module &M) {
+ auto &Ctx = M.getContext();
+
+ llvm::hlsl::rootsig::MetadataBuilder Builder(Ctx, Elements);
+ MDNode *RootSignature = Builder.BuildRootSignature();
+ MDNode *FnPairing =
+ MDNode::get(Ctx, {ValueAsMetadata::get(Fn), RootSignature});
+
+ StringRef RootSignatureValKey = "dx.rootsignatures";
+ auto *RootSignatureValMD = M.getOrInsertNamedMetadata(RootSignatureValKey);
+ RootSignatureValMD->addOperand(FnPairing);
+}
+
} // namespace
llvm::Type *CGHLSLRuntime::convertHLSLSpecificType(const Type *T) {
@@ -453,6 +467,12 @@ void CGHLSLRuntime::emitEntryFunction(const FunctionDecl *FD,
// FIXME: Handle codegen for return type semantics.
// See: https://github.com/llvm/llvm-project/issues/57875
B.CreateRetVoid();
+
+ // Add and identify root signature to function, if applicable
+ const AttrVec &Attrs = FD->getAttrs();
+ for (const Attr *Attr : Attrs)
+ if (const auto *RSAttr = dyn_cast<HLSLRootSignatureAttr>(Attr))
+ addRootSignature(RSAttr->getElements(), EntryFn, M);
}
void CGHLSLRuntime::setHLSLFunctionAttributes(const FunctionDecl *FD,
diff --git a/clang/test/CodeGenHLSL/RootSignature.hlsl b/clang/test/CodeGenHLSL/RootSignature.hlsl
new file mode 100644
index 0000000000000..76aa2690b96a7
--- /dev/null
+++ b/clang/test/CodeGenHLSL/RootSignature.hlsl
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.3-library -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-DAG: ![[#EMPTY:]] = !{}
+[shader("compute"), RootSignature("")]
+[numthreads(1,1,1)]
+void FirstEntry() {}
+
+// CHECK-DAG: ![[#CBV:]] = !{!"CBV", i32 1, i32 0, i32 0, i32 -1, i32 4}
+// CHECK-DAG: ![[#SRV:]] = !{!"SRV", i32 4, i32 42, i32 3, i32 32, i32 0}
+// CHECK-DAG: ![[#TABLE:]] = !{!"DescriptorTable", i32 0, ![[#CBV]], ![[#SRV]]}
+// CHECK-DAG: ![[#SECOND_RS:]] = !{![[#TABLE]]}
+
+#define SampleDescriptorTable \
+ "DescriptorTable( " \
+ " CBV(b0), " \
+ " SRV(t42, space = 3, offset = 32, numDescriptors = 4, flags = 0) " \
+ ")"
+[shader("compute"), RootSignature(SampleDescriptorTable)]
+[numthreads(1,1,1)]
+void SecondEntry() {}
+
+// Sanity test to ensure no root is added for this function
+[shader("compute")]
+[numthreads(1,1,1)]
+void ThirdEntry() {}
+
+// CHECK-DAG: ![[#FIRST_ENTRY:]] = !{ptr @FirstEntry, ![[#EMPTY]]}
+// CHECK-DAG: ![[#SECOND_ENTRY:]] = !{ptr @SecondEntry, ![[#SECOND_RS]]}
+// CHECK-DAG: !dx.rootsignatures = !{![[#FIRST_ENTRY]], ![[#SECOND_ENTRY]]}
diff --git a/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h b/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
index f999a0b5eef33..d1c39b720d213 100644
--- a/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
+++ b/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
@@ -14,10 +14,16 @@
#ifndef LLVM_FRONTEND_HLSL_HLSLROOTSIGNATURE_H
#define LLVM_FRONTEND_HLSL_HLSLROOTSIGNATURE_H
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLForwardCompat.h"
#include "llvm/Support/DXILABI.h"
#include <variant>
namespace llvm {
+class LLVMContext;
+class MDNode;
+class Metadata;
+
namespace hlsl {
namespace rootsig {
@@ -122,6 +128,27 @@ using RootElement = std::variant<DescriptorTable, DescriptorTableClause>;
using ParamType = std::variant<uint32_t *, DescriptorRangeOffset *,
DescriptorRangeFlags *, ShaderVisibility *>;
+class MetadataBuilder {
+public:
+ MetadataBuilder(llvm::LLVMContext &Ctx, ArrayRef<RootElement> Elements)
+ : Ctx(Ctx), Elements(Elements) {}
+
+ /// Iterates through the elements and dispatches onto the correct Build method
+ ///
+ /// Accumulates the root signature and returns the Metadata node that is just
+ /// a list of all the elements
+ MDNode *BuildRootSignature();
+
+private:
+ /// Define the various builders for the different metadata types
+ MDNode *BuildDescriptorTable(const DescriptorTable &Table);
+ MDNode *BuildDescriptorTableClause(const DescriptorTableClause &Clause);
+
+ llvm::LLVMContext &Ctx;
+ ArrayRef<RootElement> Elements;
+ SmallVector<Metadata *> GeneratedMetadata;
+};
+
} // namespace rootsig
} // namespace hlsl
} // namespace llvm
diff --git a/llvm/lib/Frontend/HLSL/CMakeLists.txt b/llvm/lib/Frontend/HLSL/CMakeLists.txt
index eda6cb8e69a49..739bfef8dbc37 100644
--- a/llvm/lib/Frontend/HLSL/CMakeLists.txt
+++ b/llvm/lib/Frontend/HLSL/CMakeLists.txt
@@ -1,5 +1,6 @@
add_llvm_component_library(LLVMFrontendHLSL
HLSLResource.cpp
+ HLSLRootSignature.cpp
ADDITIONAL_HEADER_DIRS
${LLVM_MAIN_INCLUDE_DIR}/llvm/Frontend
diff --git a/llvm/lib/Frontend/HLSL/HLSLRootSignature.cpp b/llvm/lib/Frontend/HLSL/HLSLRootSignature.cpp
new file mode 100644
index 0000000000000..fb1a2ddc72640
--- /dev/null
+++ b/llvm/lib/Frontend/HLSL/HLSLRootSignature.cpp
@@ -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(
+ B.getInt32(llvm::to_underlying(Clause.Offset))),
+ ConstantAsMetadata::get(
+ B.getInt32(llvm::to_underlying(Clause.Flags))),
+ });
+}
+
+} // namespace rootsig
+} // namespace hlsl
+} // namespace llvm
``````````
</details>
https://github.com/llvm/llvm-project/pull/125131
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