[clang] [HLSL][RootSignature] Make Root Signature lexer keywords case-insensitive (PR #132967)

[Finn Plummer via cfe-commits]

https://github.com/inbelic created https://github.com/llvm/llvm-project/pull/132967

>From the corrections to the Root Signature specification here: https://github.com/llvm/wg-hlsl/issues/192. It was denoted that keywords are also case-insensitive in DXC.

This pr adjusts the lexer to adhere to the updated spec.

We also have a NFC to add a missing license to a file while in the area.

>From d41aefdbd13ca430cd9c1f64406b5615c662dcce Mon Sep 17 00:00:00 2001
From: Finn Plummer <finnplummer at microsoft.com>
Date: Tue, 25 Mar 2025 16:23:25 +0000
Subject: [PATCH 1/2] [NFC] add missing liscence to file

---
 clang/lib/Lex/LexHLSLRootSignature.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/clang/lib/Lex/LexHLSLRootSignature.cpp b/clang/lib/Lex/LexHLSLRootSignature.cpp
index 8344aad15a9bc..81a8c74ce1be3 100644
--- a/clang/lib/Lex/LexHLSLRootSignature.cpp
+++ b/clang/lib/Lex/LexHLSLRootSignature.cpp
@@ -1,3 +1,11 @@
+//=== LexHLSLRootSignature.cpp - Lex Root Signature -----------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
 #include "clang/Lex/LexHLSLRootSignature.h"
 
 namespace clang {

>From cfe69b115871dc1a3d9de6d4c62b3c963597acc0 Mon Sep 17 00:00:00 2001
From: Finn Plummer <finnplummer at microsoft.com>
Date: Tue, 25 Mar 2025 16:24:50 +0000
Subject: [PATCH 2/2] [HLSL][RootSignature] Make keywords case-insensitive

- from dxc testing, it was shown that keywords could be specified in a
case-insensitive manner. the current implementation was case sensitive
---
 clang/lib/Lex/LexHLSLRootSignature.cpp        |  2 +-
 .../Lex/LexHLSLRootSignatureTest.cpp          | 30 +++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Lex/LexHLSLRootSignature.cpp b/clang/lib/Lex/LexHLSLRootSignature.cpp
index 81a8c74ce1be3..fb4aab20c7275 100644
--- a/clang/lib/Lex/LexHLSLRootSignature.cpp
+++ b/clang/lib/Lex/LexHLSLRootSignature.cpp
@@ -95,7 +95,7 @@ RootSignatureToken RootSignatureLexer::LexToken() {
 
   // Define a large string switch statement for all the keywords and enums
   auto Switch = llvm::StringSwitch<TokenKind>(TokSpelling);
-#define KEYWORD(NAME) Switch.Case(#NAME, TokenKind::kw_##NAME);
+#define KEYWORD(NAME) Switch.CaseLower(#NAME, TokenKind::kw_##NAME);
 #define ENUM(NAME, LIT) Switch.CaseLower(LIT, TokenKind::en_##NAME);
 #include "clang/Lex/HLSLRootSignatureTokenKinds.def"
 
diff --git a/clang/unittests/Lex/LexHLSLRootSignatureTest.cpp b/clang/unittests/Lex/LexHLSLRootSignatureTest.cpp
index 0576f08c4c276..d72a842922f98 100644
--- a/clang/unittests/Lex/LexHLSLRootSignatureTest.cpp
+++ b/clang/unittests/Lex/LexHLSLRootSignatureTest.cpp
@@ -120,6 +120,36 @@ TEST_F(LexHLSLRootSignatureTest, ValidLexAllTokensTest) {
   CheckTokens(Lexer, Tokens, Expected);
 }
 
+TEST_F(LexHLSLRootSignatureTest, ValidCaseInsensitiveKeywordsTest) {
+  // This test will check that we can lex keywords in an case-insensitive
+  // manner
+  const llvm::StringLiteral Source = R"cc(
+    DeScRiPtOrTaBlE
+
+    CBV srv UAV sampler
+    SPACE visibility FLAGS
+    numDescriptors OFFSET
+  )cc";
+  auto TokLoc = SourceLocation();
+  hlsl::RootSignatureLexer Lexer(Source, TokLoc);
+
+  SmallVector<hlsl::RootSignatureToken> Tokens;
+  SmallVector<hlsl::TokenKind> Expected = {
+      hlsl::TokenKind::kw_DescriptorTable,
+      hlsl::TokenKind::kw_CBV,
+      hlsl::TokenKind::kw_SRV,
+      hlsl::TokenKind::kw_UAV,
+      hlsl::TokenKind::kw_Sampler,
+      hlsl::TokenKind::kw_space,
+      hlsl::TokenKind::kw_visibility,
+      hlsl::TokenKind::kw_flags,
+      hlsl::TokenKind::kw_numDescriptors,
+      hlsl::TokenKind::kw_offset,
+  };
+
+  CheckTokens(Lexer, Tokens, Expected);
+}
+
 TEST_F(LexHLSLRootSignatureTest, ValidLexPeekTest) {
   // This test will check that we the peek api is correctly used
   const llvm::StringLiteral Source = R"cc(