Improve handling of `SampleCmpLevelZero`

- We map `SampleCmpLevelZero` to either `textureLod` or `textureGrad` based on what the GLSL spec seems to allow

- We map `SamplerComparisonState` to `samplerShadow` (instead of just `sampler`)

2 files changed, 61 insertions, 2 deletions

diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index effa9aa97..c6efa88dc 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -1041,7 +1041,7 @@ struct EmitVisitor
         default:
             switch (samplerStateType->flavor)
             {
-            case SamplerStateType::Flavor::SamplerState:			Emit("SamplerState");				break;
+            case SamplerStateType::Flavor::SamplerState:			Emit("SamplerState");			break;
             case SamplerStateType::Flavor::SamplerComparisonState:	Emit("SamplerComparisonState");	break;
             default:
                 assert(!"unreachable");
@@ -1050,7 +1050,15 @@ struct EmitVisitor
             break;
 
         case CodeGenTarget::GLSL:
-            Emit("sampler");
+            switch (samplerStateType->flavor)
+            {
+            case SamplerStateType::Flavor::SamplerState:			Emit("sampler");		break;
+            case SamplerStateType::Flavor::SamplerComparisonState:	Emit("samplerShadow");	break;
+            default:
+                assert(!"unreachable");
+                break;
+            }
+            break;
             break;
         }
 
@@ -1847,6 +1855,15 @@ struct EmitVisitor
                                     if (auto baseTextureType = base->Type->As<TextureType>())
                                     {
                                         emitGLSLTextureOrTextureSamplerType(baseTextureType, "sampler");
+
+                                        if (auto samplerType = callExpr->Arguments[0]->Type.type->As<SamplerStateType>())
+                                        {
+                                            if (samplerType->flavor == SamplerStateType::Flavor::SamplerComparisonState)
+                                            {
+                                                Emit("Shadow");
+                                            }
+                                        }
+
                                         Emit("(");
                                         EmitExpr(memberExpr->BaseExpression);
                                         Emit(",");
diff --git a/source/slang/slang-stdlib.cpp b/source/slang/slang-stdlib.cpp
index 1c1bcceaf..169eac4fb 100644
--- a/source/slang/slang-stdlib.cpp
+++ b/source/slang/slang-stdlib.cpp
@@ -1612,6 +1612,48 @@ namespace Slang
                         sb << "float compareValue";
                         sb << ");\n";
 
+                        int baseCoordCount = kBaseTextureTypes[tt].coordCount;
+                        int arrCoordCount = baseCoordCount + isArray;
+                        if (arrCoordCount < 3)
+                        {
+                            int extCoordCount = arrCoordCount + 1;
+
+                            if (extCoordCount < 3)
+                                extCoordCount = 3;
+
+                            sb << "__intrinsic(glsl, \"textureLod($p, ";
+
+                            sb << "vec" << extCoordCount << "($1,";
+                            for (int ii = arrCoordCount; ii < extCoordCount - 1; ++ii)
+                            {
+                                sb << " 0.0,";
+                            }
+                            sb << "$2)";
+
+                            sb << ", 0.0)\")\n";
+                        }
+                        else if(arrCoordCount <= 3)
+                        {
+                            int extCoordCount = arrCoordCount + 1;
+
+                            if (extCoordCount < 3)
+                                extCoordCount = 3;
+
+                            sb << "__intrinsic(glsl, \"textureGrad($p, ";
+
+                            sb << "vec" << extCoordCount << "($1,";
+                            for (int ii = arrCoordCount; ii < extCoordCount - 1; ++ii)
+                            {
+                                sb << " 0.0,";
+                            }
+                            sb << "$2)";
+
+                            // Construct gradients
+                            sb << ", vec" << baseCoordCount << "(0.0)";
+                            sb << ", vec" << baseCoordCount << "(0.0)";
+                            sb << ")\")\n";
+                        }
+                        sb << "__intrinsic\n";
                         sb << "T SampleCmpLevelZero(SamplerComparisonState s, ";
                         sb << "float" << kBaseTextureTypes[tt].coordCount + isArray << " location, ";
                         sb << "float compareValue";