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

[Finn Plummer via cfe-commits]

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@@ -0,0 +1,171 @@
+#include "clang/Parse/ParseHLSLRootSignature.h"
+
+namespace clang {
+namespace hlsl {
+
+// Lexer Definitions
+
+static bool IsNumberChar(char C) {
+  // TODO(#120472): extend for float support exponents
+  return isdigit(C); // integer support
+}
+
+bool RootSignatureLexer::LexNumber(RootSignatureToken &Result) {
+  // NumericLiteralParser does not handle the sign so we will manually apply it
+  bool Negative = Buffer.front() == '-';
+  bool Signed = Negative || Buffer.front() == '+';
+  if (Signed)
+    AdvanceBuffer();
+
+  // Retrieve the possible number
+  StringRef NumSpelling = Buffer.take_while(IsNumberChar);
+
+  // Catch this now as the Literal Parser will accept it as valid
+  if (NumSpelling.empty()) {
+    PP.getDiagnostics().Report(Result.TokLoc,
+                               diag::err_hlsl_invalid_number_literal);
+    return true;
+  }
+
+  // Parse the numeric value and do 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
+
+  // Note: if IsNumberChar allows for hexidecimal we will need to turn this
+  // into a diagnostics for potential fixed-point literals
+  assert(Literal.isIntegerLiteral() && "IsNumberChar will only support digits");
+
+  // Retrieve the number value to store into the token
+  Result.Kind = TokenKind::int_literal;
+
+  // NOTE: for compabibility with DXC, we will treat any integer with '+' as an
+  // unsigned integer
+  llvm::APSInt X = llvm::APSInt(32, !Negative);
+  if (Literal.GetIntegerValue(X)) {
+    // Report that the value has overflowed
+    PP.getDiagnostics().Report(Result.TokLoc,
+                               diag::err_hlsl_number_literal_overflow)
+        << (unsigned)Signed << NumSpelling;
+    return true;
+  }
+
+  X = Negative ? -X : X;
+  Result.NumLiteral = APValue(X);
+
+  AdvanceBuffer(NumSpelling.size());
+  return false;
+}
+
+bool RootSignatureLexer::Lex(SmallVector<RootSignatureToken> &Tokens) {
+  // Discard any leading whitespace
+  AdvanceBuffer(Buffer.take_while(isspace).size());
+
+  while (!Buffer.empty()) {
+    // Record where this token is in the text for usage in parser diagnostics
+    RootSignatureToken Result(SourceLoc);
+    if (LexToken(Result))
+      return true;
+
+    // Successfully Lexed the token so we can store it
+    Tokens.push_back(Result);
+
+    // Discard any trailing whitespace
+    AdvanceBuffer(Buffer.take_while(isspace).size());
+  }
+
+  return false;
+}
+
+bool RootSignatureLexer::LexToken(RootSignatureToken &Result) {
+  char C = Buffer.front();
+
+  // Punctuators
+  switch (C) {
+#define PUNCTUATOR(X, Y)                                                       \
+  case Y: {                                                                    \
+    Result.Kind = TokenKind::pu_##X;                                           \
+    AdvanceBuffer();                                                           \
+    return false;                                                              \
+  }
+#include "clang/Parse/HLSLRootSignatureTokenKinds.def"
+  default:
+    break;
+  }
+
+  // Numeric constant
+  if (isdigit(C) || C == '-' || C == '+')
+    return LexNumber(Result);
+
+  // All following tokens require at least one additional character
+  if (Buffer.size() <= 1) {
+    PP.getDiagnostics().Report(Result.TokLoc, diag::err_hlsl_invalid_token);
----------------
inbelic wrote:

Would you also remove the same error message from [here](https://github.com/llvm/llvm-project/blob/d648f4ccb8c74060e9e6d75b46f54ac0127e4302/clang/lib/Parse/ParseHLSLRootSignature.cpp#L161)?

They were added just to have _some_ indication that lexing failed.

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