[clang] [HLSL][RootSignature] Implement Lexing of DescriptorTables (PR #122981)

[Finn Plummer via cfe-commits]

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@@ -0,0 +1,152 @@
+#include "clang/Parse/ParseHLSLRootSignature.h"
+
+namespace llvm {
+namespace hlsl {
+namespace root_signature {
+
+// Lexer Definitions
+
+static bool IsPreprocessorNumberChar(char C) {
+  // TODO: extend for float support with or without hexadecimal/exponent
+  return isdigit(C); // integer support
+}
+
+bool RootSignatureLexer::LexNumber(RootSignatureToken &Result) {
+  // NumericLiteralParser does not handle the sign so we will manually apply it
+  Result.Signed = Buffer.front() == '-';
+  if (Result.Signed)
+    AdvanceBuffer();
+
+  // Retrieve the possible number
+  StringRef NumSpelling = Buffer.take_while(IsPreprocessorNumberChar);
+
+  // Parse the numeric value and so semantic checks on its specification
+  clang::NumericLiteralParser Literal(NumSpelling, SourceLoc,
+                                      PP.getSourceManager(), PP.getLangOpts(),
+                                      PP.getTargetInfo(), PP.getDiagnostics());
+  if (Literal.hadError)
+    return true; // Error has already been reported so just return
+
+  // Retrieve the number value to store into the token
+  if (Literal.isIntegerLiteral()) {
+    Result.Kind = TokenKind::int_literal;
+
+    APSInt X = APSInt(32, Result.Signed);
+    if (Literal.GetIntegerValue(X))
+      return true; // TODO: Report overflow error
+
+    X = Result.Signed ? -X : X;
+    Result.IntLiteral = (uint32_t)X.getZExtValue();
+  } else {
+    return true; // TODO: report unsupported number literal specification
+  }
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inbelic wrote:

That follows the rest of the code conventions, thanks.

https://github.com/llvm/llvm-project/pull/122981