review: dealing with signed positive integer

- the previous implementation would not have thrown an overflow error as
expected. Instead it would have been treated as a negative int
- DXC treats all positively signed ints as an unsigned integer, so for
compatibility, we will be doing the same.
- add better unit tests to demonstrate expected functionality

Author: inbelic

clang/lib/Parse/ParseHLSLRootSignature.cpp

@@ -41,7 +41,9 @@ bool RootSignatureLexer::LexNumber(RootSignatureToken &Result) {
   // Retrieve the number value to store into the token
   Result.Kind = TokenKind::int_literal;
 
-  llvm::APSInt X = llvm::APSInt(32, !Signed);
+  // 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,

clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp

@@ -115,7 +115,7 @@ class ParseHLSLRootSignatureTest : public ::testing::Test {
 TEST_F(ParseHLSLRootSignatureTest, ValidLexNumbersTest) {
   // This test will check that we can lex different number tokens
   const llvm::StringLiteral Source = R"cc(
-    -42 42 +42
+    -42 42 +42 +2147483648
   )cc";
 
   TrivialModuleLoader ModLoader;
@@ -135,8 +135,30 @@ TEST_F(ParseHLSLRootSignatureTest, ValidLexNumbersTest) {
       hlsl::TokenKind::int_literal,
       hlsl::TokenKind::int_literal,
       hlsl::TokenKind::int_literal,
+      hlsl::TokenKind::int_literal,
   };
   CheckTokens(Tokens, Expected);
+
+  // Sample negative int
+  hlsl::RootSignatureToken IntToken = Tokens[0];
+  ASSERT_TRUE(IntToken.NumLiteral.getInt().isSigned());
+  ASSERT_EQ(IntToken.NumLiteral.getInt().getExtValue(), -42);
+
+  // Sample unsigned int
+  IntToken = Tokens[1];
+  ASSERT_FALSE(IntToken.NumLiteral.getInt().isSigned());
+  ASSERT_EQ(IntToken.NumLiteral.getInt().getExtValue(), 42);
+
+  // Sample positive int that is treated as unsigned
+  IntToken = Tokens[2];
+  ASSERT_FALSE(IntToken.NumLiteral.getInt().isSigned());
+  ASSERT_EQ(IntToken.NumLiteral.getInt().getExtValue(), 42);
+
+  // Sample positive int that would overflow the signed representation but
+  // is treated as an unsigned integer instead
+  IntToken = Tokens[3];
+  ASSERT_FALSE(IntToken.NumLiteral.getInt().isSigned());
+  ASSERT_EQ(IntToken.NumLiteral.getInt().getExtValue(), 2147483648);
 }
 
 TEST_F(ParseHLSLRootSignatureTest, ValidLexAllTokensTest) {