[llvm-branch-commits] [clang] [llvm] [HLSL][RootSignature] Add mandatory parameters for RootConstants (PR #138002)

Finn Plummer via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Wed Apr 30 11:08:43 PDT 2025


https://github.com/inbelic updated https://github.com/llvm/llvm-project/pull/138002

>From 15857bf8e1303e2325b48e417e7abd26aa77910e Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Wed, 30 Apr 2025 17:53:11 +0000
Subject: [PATCH 1/2] [HLSL][RootSignature] Add mandatory parameters for
 RootConstants

- defines the `parseRootConstantParams` function and adds handling for
the mandatory arguments of `num32BitConstants` and `bReg`

- adds corresponding unit tests

Part two of implementing
---
 .../clang/Parse/ParseHLSLRootSignature.h      | 10 ++-
 clang/lib/Parse/ParseHLSLRootSignature.cpp    | 68 ++++++++++++++++++-
 .../Parse/ParseHLSLRootSignatureTest.cpp      | 14 +++-
 .../llvm/Frontend/HLSL/HLSLRootSignature.h    |  5 +-
 4 files changed, 89 insertions(+), 8 deletions(-)

diff --git a/clang/include/clang/Parse/ParseHLSLRootSignature.h b/clang/include/clang/Parse/ParseHLSLRootSignature.h
index efa735ea03d94..0f05b05ed4df6 100644
--- a/clang/include/clang/Parse/ParseHLSLRootSignature.h
+++ b/clang/include/clang/Parse/ParseHLSLRootSignature.h
@@ -77,8 +77,14 @@ class RootSignatureParser {
   parseDescriptorTableClause();
 
   /// Parameter arguments (eg. `bReg`, `space`, ...) can be specified in any
-  /// order and only exactly once. `ParsedClauseParams` denotes the current
-  /// state of parsed params
+  /// order and only exactly once. The following methods define a
+  /// `Parsed.*Params` struct to denote the current state of parsed params
+  struct ParsedConstantParams {
+    std::optional<llvm::hlsl::rootsig::Register> Reg;
+    std::optional<uint32_t> Num32BitConstants;
+  };
+  std::optional<ParsedConstantParams> parseRootConstantParams();
+
   struct ParsedClauseParams {
     std::optional<llvm::hlsl::rootsig::Register> Reg;
     std::optional<uint32_t> NumDescriptors;
diff --git a/clang/lib/Parse/ParseHLSLRootSignature.cpp b/clang/lib/Parse/ParseHLSLRootSignature.cpp
index 48d3e38b0519d..2ce8e6e5cca98 100644
--- a/clang/lib/Parse/ParseHLSLRootSignature.cpp
+++ b/clang/lib/Parse/ParseHLSLRootSignature.cpp
@@ -57,6 +57,27 @@ std::optional<RootConstants> RootSignatureParser::parseRootConstants() {
 
   RootConstants Constants;
 
+  auto Params = parseRootConstantParams();
+  if (!Params.has_value())
+    return std::nullopt;
+
+  // Check mandatory parameters were provided
+  if (!Params->Num32BitConstants.has_value()) {
+    getDiags().Report(CurToken.TokLoc, diag::err_hlsl_rootsig_missing_param)
+        << TokenKind::kw_num32BitConstants;
+    return std::nullopt;
+  }
+
+  Constants.Num32BitConstants = Params->Num32BitConstants.value();
+
+  if (!Params->Reg.has_value()) {
+    getDiags().Report(CurToken.TokLoc, diag::err_hlsl_rootsig_missing_param)
+        << TokenKind::bReg;
+    return std::nullopt;
+  }
+
+  Constants.Reg = Params->Reg.value();
+
   if (consumeExpectedToken(TokenKind::pu_r_paren,
                            diag::err_hlsl_unexpected_end_of_params,
                            /*param of=*/TokenKind::kw_RootConstants))
@@ -187,14 +208,55 @@ RootSignatureParser::parseDescriptorTableClause() {
   return Clause;
 }
 
+// Parameter arguments (eg. `bReg`, `space`, ...) can be specified in any
+// order and only exactly once. The following methods will parse through as
+// many arguments as possible reporting an error if a duplicate is seen.
+std::optional<RootSignatureParser::ParsedConstantParams>
+RootSignatureParser::parseRootConstantParams() {
+  assert(CurToken.TokKind == TokenKind::pu_l_paren &&
+         "Expects to only be invoked starting at given token");
+
+  ParsedConstantParams Params;
+  do {
+    // `num32BitConstants` `=` POS_INT
+    if (tryConsumeExpectedToken(TokenKind::kw_num32BitConstants)) {
+      if (Params.Num32BitConstants.has_value()) {
+        getDiags().Report(CurToken.TokLoc, diag::err_hlsl_rootsig_repeat_param)
+            << CurToken.TokKind;
+        return std::nullopt;
+      }
+
+      if (consumeExpectedToken(TokenKind::pu_equal))
+        return std::nullopt;
+
+      auto Num32BitConstants = parseUIntParam();
+      if (!Num32BitConstants.has_value())
+        return std::nullopt;
+      Params.Num32BitConstants = Num32BitConstants;
+    }
+
+    // `b` POS_INT
+    if (tryConsumeExpectedToken(TokenKind::bReg)) {
+      if (Params.Reg.has_value()) {
+        getDiags().Report(CurToken.TokLoc, diag::err_hlsl_rootsig_repeat_param)
+            << CurToken.TokKind;
+        return std::nullopt;
+      }
+      auto Reg = parseRegister();
+      if (!Reg.has_value())
+        return std::nullopt;
+      Params.Reg = Reg;
+    }
+  } while (tryConsumeExpectedToken(TokenKind::pu_comma));
+
+  return Params;
+}
+
 std::optional<RootSignatureParser::ParsedClauseParams>
 RootSignatureParser::parseDescriptorTableClauseParams(TokenKind RegType) {
   assert(CurToken.TokKind == TokenKind::pu_l_paren &&
          "Expects to only be invoked starting at given token");
 
-  // Parameter arguments (eg. `bReg`, `space`, ...) can be specified in any
-  // order and only exactly once. Parse through as many arguments as possible
-  // reporting an error if a duplicate is seen.
   ParsedClauseParams Params;
   do {
     // ( `b` | `t` | `u` | `s`) POS_INT
diff --git a/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp b/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp
index 0a7d8ac86cc5f..336868b579866 100644
--- a/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp
+++ b/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp
@@ -254,7 +254,8 @@ TEST_F(ParseHLSLRootSignatureTest, ValidSamplerFlagsTest) {
 
 TEST_F(ParseHLSLRootSignatureTest, ValidParseRootConsantsTest) {
   const llvm::StringLiteral Source = R"cc(
-    RootConstants()
+    RootConstants(num32BitConstants = 1, b0),
+    RootConstants(b42, num32BitConstants = 4294967295)
   )cc";
 
   TrivialModuleLoader ModLoader;
@@ -270,10 +271,19 @@ TEST_F(ParseHLSLRootSignatureTest, ValidParseRootConsantsTest) {
 
   ASSERT_FALSE(Parser.parse());
 
-  ASSERT_EQ(Elements.size(), 1u);
+  ASSERT_EQ(Elements.size(), 2u);
 
   RootElement Elem = Elements[0];
   ASSERT_TRUE(std::holds_alternative<RootConstants>(Elem));
+  ASSERT_EQ(std::get<RootConstants>(Elem).Num32BitConstants, 1u);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Reg.ViewType, RegisterType::BReg);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Reg.Number, 0u);
+
+  Elem = Elements[1];
+  ASSERT_TRUE(std::holds_alternative<RootConstants>(Elem));
+  ASSERT_EQ(std::get<RootConstants>(Elem).Num32BitConstants, 4294967295u);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Reg.ViewType, RegisterType::BReg);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Reg.Number, 42u);
 
   ASSERT_TRUE(Consumer->isSatisfied());
 }
diff --git a/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h b/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
index 05735fa75b318..a3f98a9f1944f 100644
--- a/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
+++ b/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
@@ -55,7 +55,10 @@ struct Register {
 };
 
 // Models the parameter values of root constants
-struct RootConstants {};
+struct RootConstants {
+  uint32_t Num32BitConstants;
+  Register Reg;
+};
 
 // Models the end of a descriptor table and stores its visibility
 struct DescriptorTable {

>From f8011807d233d1d0d1f9d4ce08bad0c559cde74a Mon Sep 17 00:00:00 2001
From: Finn Plummer <canadienfinn at gmail.com>
Date: Wed, 30 Apr 2025 18:08:31 +0000
Subject: [PATCH 2/2] [HLSL][RootSignature] Add optional parameter for
 RootConstants

- extends `parseRootConstantParams` and the struct to include the
optional parameters of a RootConstant

- adds corresponding unit tests
---
 .../clang/Parse/ParseHLSLRootSignature.h      |  2 +
 clang/lib/Parse/ParseHLSLRootSignature.cpp    | 41 +++++++++++++++++++
 .../Parse/ParseHLSLRootSignatureTest.cpp      |  8 +++-
 .../llvm/Frontend/HLSL/HLSLRootSignature.h    |  2 +
 4 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/clang/include/clang/Parse/ParseHLSLRootSignature.h b/clang/include/clang/Parse/ParseHLSLRootSignature.h
index 0f05b05ed4df6..2ac2083983741 100644
--- a/clang/include/clang/Parse/ParseHLSLRootSignature.h
+++ b/clang/include/clang/Parse/ParseHLSLRootSignature.h
@@ -82,6 +82,8 @@ class RootSignatureParser {
   struct ParsedConstantParams {
     std::optional<llvm::hlsl::rootsig::Register> Reg;
     std::optional<uint32_t> Num32BitConstants;
+    std::optional<uint32_t> Space;
+    std::optional<llvm::hlsl::rootsig::ShaderVisibility> Visibility;
   };
   std::optional<ParsedConstantParams> parseRootConstantParams();
 
diff --git a/clang/lib/Parse/ParseHLSLRootSignature.cpp b/clang/lib/Parse/ParseHLSLRootSignature.cpp
index 2ce8e6e5cca98..a5006b77a6e44 100644
--- a/clang/lib/Parse/ParseHLSLRootSignature.cpp
+++ b/clang/lib/Parse/ParseHLSLRootSignature.cpp
@@ -78,6 +78,13 @@ std::optional<RootConstants> RootSignatureParser::parseRootConstants() {
 
   Constants.Reg = Params->Reg.value();
 
+  // Fill in optional parameters
+  if (Params->Visibility.has_value())
+    Constants.Visibility = Params->Visibility.value();
+
+  if (Params->Space.has_value())
+    Constants.Space = Params->Space.value();
+
   if (consumeExpectedToken(TokenKind::pu_r_paren,
                            diag::err_hlsl_unexpected_end_of_params,
                            /*param of=*/TokenKind::kw_RootConstants))
@@ -247,6 +254,40 @@ RootSignatureParser::parseRootConstantParams() {
         return std::nullopt;
       Params.Reg = Reg;
     }
+
+    // `space` `=` POS_INT
+    if (tryConsumeExpectedToken(TokenKind::kw_space)) {
+      if (Params.Space.has_value()) {
+        getDiags().Report(CurToken.TokLoc, diag::err_hlsl_rootsig_repeat_param)
+            << CurToken.TokKind;
+        return std::nullopt;
+      }
+
+      if (consumeExpectedToken(TokenKind::pu_equal))
+        return std::nullopt;
+
+      auto Space = parseUIntParam();
+      if (!Space.has_value())
+        return std::nullopt;
+      Params.Space = Space;
+    }
+
+    // `visibility` `=` SHADER_VISIBILITY
+    if (tryConsumeExpectedToken(TokenKind::kw_visibility)) {
+      if (Params.Visibility.has_value()) {
+        getDiags().Report(CurToken.TokLoc, diag::err_hlsl_rootsig_repeat_param)
+            << CurToken.TokKind;
+        return std::nullopt;
+      }
+
+      if (consumeExpectedToken(TokenKind::pu_equal))
+        return std::nullopt;
+
+      auto Visibility = parseShaderVisibility();
+      if (!Visibility.has_value())
+        return std::nullopt;
+      Params.Visibility = Visibility;
+    }
   } while (tryConsumeExpectedToken(TokenKind::pu_comma));
 
   return Params;
diff --git a/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp b/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp
index 336868b579866..150eb3e6e54ef 100644
--- a/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp
+++ b/clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp
@@ -255,7 +255,9 @@ TEST_F(ParseHLSLRootSignatureTest, ValidSamplerFlagsTest) {
 TEST_F(ParseHLSLRootSignatureTest, ValidParseRootConsantsTest) {
   const llvm::StringLiteral Source = R"cc(
     RootConstants(num32BitConstants = 1, b0),
-    RootConstants(b42, num32BitConstants = 4294967295)
+    RootConstants(b42, space = 3, num32BitConstants = 4294967295,
+      visibility = SHADER_VISIBILITY_HULL
+    )
   )cc";
 
   TrivialModuleLoader ModLoader;
@@ -278,12 +280,16 @@ TEST_F(ParseHLSLRootSignatureTest, ValidParseRootConsantsTest) {
   ASSERT_EQ(std::get<RootConstants>(Elem).Num32BitConstants, 1u);
   ASSERT_EQ(std::get<RootConstants>(Elem).Reg.ViewType, RegisterType::BReg);
   ASSERT_EQ(std::get<RootConstants>(Elem).Reg.Number, 0u);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Space, 0u);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Visibility, ShaderVisibility::All);
 
   Elem = Elements[1];
   ASSERT_TRUE(std::holds_alternative<RootConstants>(Elem));
   ASSERT_EQ(std::get<RootConstants>(Elem).Num32BitConstants, 4294967295u);
   ASSERT_EQ(std::get<RootConstants>(Elem).Reg.ViewType, RegisterType::BReg);
   ASSERT_EQ(std::get<RootConstants>(Elem).Reg.Number, 42u);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Space, 3u);
+  ASSERT_EQ(std::get<RootConstants>(Elem).Visibility, ShaderVisibility::Hull);
 
   ASSERT_TRUE(Consumer->isSatisfied());
 }
diff --git a/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h b/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
index a3f98a9f1944f..8b8324df18bb3 100644
--- a/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
+++ b/llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h
@@ -58,6 +58,8 @@ struct Register {
 struct RootConstants {
   uint32_t Num32BitConstants;
   Register Reg;
+  uint32_t Space = 0;
+  ShaderVisibility Visibility = ShaderVisibility::All;
 };
 
 // Models the end of a descriptor table and stores its visibility



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