add parsing for minLOD

Author: inbelic

clang/include/clang/Parse/ParseHLSLRootSignature.h

@@ -113,6 +113,7 @@ class RootSignatureParser {
     std::optional<llvm::hlsl::rootsig::Register> Reg;
     std::optional<float> MipLODBias;
     std::optional<uint32_t> MaxAnisotropy;
+    std::optional<float> MinLOD;
   };
   std::optional<ParsedStaticSamplerParams> parseStaticSamplerParams();
 

clang/lib/Parse/ParseHLSLRootSignature.cpp

@@ -387,6 +387,9 @@ std::optional<StaticSampler> RootSignatureParser::parseStaticSampler() {
   if (Params->MaxAnisotropy.has_value())
     Sampler.MaxAnisotropy= Params->MaxAnisotropy.value();
 
+  if (Params->MinLOD.has_value())
+    Sampler.MinLOD= Params->MinLOD.value();
+
   if (consumeExpectedToken(TokenKind::pu_r_paren,
                            diag::err_hlsl_unexpected_end_of_params,
                            /*param of=*/TokenKind::kw_StaticSampler))
@@ -706,6 +709,23 @@ RootSignatureParser::parseStaticSamplerParams() {
         return std::nullopt;
       Params.MaxAnisotropy = MaxAnisotropy;
     }
+
+    // `minLOD` `=` NUMBER
+    if (tryConsumeExpectedToken(TokenKind::kw_minLOD)) {
+      if (Params.MinLOD.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 MinLOD= parseFloatParam();
+      if (!MinLOD.has_value())
+        return std::nullopt;
+      Params.MinLOD = MinLOD;
+    }
   } while (tryConsumeExpectedToken(TokenKind::pu_comma));
 
   return Params;

llvm/include/llvm/Frontend/HLSL/HLSLRootSignature.h

@@ -162,6 +162,7 @@ struct StaticSampler {
   Register Reg;
   float MipLODBias = 0.f;
   uint32_t MaxAnisotropy = 16;
+  float MinLOD = 0.f;
 };
 
 /// Models RootElement : RootFlags | RootConstants | RootParam