Add hacky GLSL lowering for `GetDimensions`

This is hacky for two big reasons:

1. It uses "operator comma" in the output to deal with calling multiple functions in an expression context

2. The way I'm lowering things to GLSL ends up using certain function arguments more than once, which means they get emitted as GLSL more than once, which means their *side effects* get evaluated more than once. Please don't put an expression with side effects in as an argument to `GetDimensions` when cross-compiling.

Solving these issues requires the translation of builtins to be more directly handled as part of lowering, rather than a purely textual operation done during emission. I don't have time to fix that right now.

1 files changed, 60 insertions, 0 deletions

diff --git a/source/slang/slang-stdlib.cpp b/source/slang/slang-stdlib.cpp
index 169eac4fb..4fcef6639 100644
--- a/source/slang/slang-stdlib.cpp
+++ b/source/slang/slang-stdlib.cpp
@@ -1440,6 +1440,66 @@ namespace Slang
                     for(int isFloat = 0; isFloat < 2; ++isFloat)
                     for(int includeMipInfo = 0; includeMipInfo < 2; ++includeMipInfo)
                     {
+                        {
+                            sb << "__intrinsic(glsl, \"(";
+
+                            int aa = 0;
+                            String lodStr = "0";
+                            if (includeMipInfo)
+                            {
+                                int mipLevelArg = aa++;
+                                lodStr.append("$");
+                                lodStr.append(mipLevelArg);
+                            }
+
+                            int cc = 0;
+                            switch(baseShape)
+                            {
+                            case TextureType::Shape1D:
+                                sb << "($" << aa++ << " = textureSize($P, " << lodStr << "))";
+                                cc = 1;
+                                break;
+
+                            case TextureType::Shape2D:
+                            case TextureType::ShapeCube:
+                                sb << "($" << aa++ << " = textureSize($P, " << lodStr << ").x)";
+                                sb << ", ($" << aa++ << " = textureSize($P, " << lodStr << ").y)";
+                                cc = 2;
+                                break;
+
+                            case TextureType::Shape3D:
+                                sb << "($" << aa++ << " = textureSize($P, " << lodStr << ").x)";
+                                sb << ", ($" << aa++ << " = textureSize($P, " << lodStr << ").y)";
+                                sb << ", ($" << aa++ << " = textureSize($P, " << lodStr << ").z)";
+                                cc = 3;
+                                break;
+
+                            default:
+                                assert(!"unexpected");
+                                break;
+                            }
+
+                            if(isArray)
+                            {
+                                sb << ", ($" << aa++ << " = textureSize($P, " << lodStr << ")." << kComponentNames[cc] << ")";
+                            }
+
+                            if(isMultisample)
+                            {
+                                sb << ", ($" << aa++ << " = textureSamples($P))";
+                            }
+
+                            if (includeMipInfo)
+                            {
+                                sb << ", ($" << aa++ << " = textureQueryLevels($P))";
+                            }
+
+
+                            sb << ")\")\n";
+                            sb << "__intrinsic\n";
+
+                        }
+
                         char const* t = isFloat ? "out float " : "out uint ";
 
                         sb << "void GetDimensions(";