Expand upon existing `ImageSubscript` support (Metal, GLSL, SPIRV) (#4408)

* Add additional `ImageSubscript` features:

1. Added ImageSubscript support for Metal & a test case
    * Merge GLSL/SPIRV/Metal `ImageSubscript` legalization pass
2. Added multisample support to glsl/spirv/metal for when using ImageSubscript
    * Added in this PR since the overhaul of the code merges together GLSL/SPIRV/Metal implementation
3. Fixed minor metal texture `Load`/`Read` bugs
    * [HLSL methods of access do not support subscript accessor for texture cube array](https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/texturecubearray)
    * removed swizzling of uint/int/float
    * other odd bugs which were causing compile errors

note: Compute tests do not work due to what seems to be the GFX backend (causes crash without error report). The tests are disabled.

* disable LOD with texture 1d

seems that LOD for 1d textures need to be a compile time constant as per an error metal throws

* syntax error in hlsl.meta

* static_assert alone with intrinsic_asm error

provides cleaner errors
Note: `static_assert` seems to be unstable and not be fully respected (still require `intrinsic_asm` to avoid a stdlib compile error)

* change comment to `// lod is not supported for 1D texture

* add `static_assert` in related code gen paths

* address review

* address review

* add asserts as per review comment, NOTE: unclear if these should be release 'asserts' as well

1 files changed, 13 insertions, 18 deletions

diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index 597e4dc06..94a5208b0 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -2416,11 +2416,12 @@ extension __TextureImpl<T,Shape,isArray,0,sampleCount,0,isShadow,isCombined,form
                     __intrinsic_asm "$c$0.read(vec<uint,3>(($1).xyz), uint(($1).w))$z";
                 break;
             case $(SLANG_TEXTURE_CUBE):
+                static_assert(isArray == 0, "Unsupported 'Load' of 'texture cube array' for 'metal' target");
                 if (isShadow == 1)
                 {
                     if (isArray == 1)
                         // T read(uint2 coord, uint face, uint array, uint lod = 0) const
-                        __intrinsic_asm "$0.read(vec<uint,2>(($1).xy), uint(($1).z), uint(($1).w))";
+                        __intrinsic_asm "<invalid intrinsics>";
                     else
                         // T read(uint2 coord, uint face, uint lod = 0) const
                         __intrinsic_asm "$c$0.read(vec<uint,2>(($1).xy), uint(($1).z), uint(($1).w))$z";
@@ -2429,14 +2430,14 @@ extension __TextureImpl<T,Shape,isArray,0,sampleCount,0,isShadow,isCombined,form
                 {
                     if (isArray == 1)
                         // Tv read(uint2 coord, uint face, uint array, uint lod = 0) const
-                        __intrinsic_asm "$0.read(vec<uint,2>(($1).xy), uint(($1).z), uint(($1).w))";
+                        __intrinsic_asm "<invalid intrinsics>";
                     else
                         // Tv read(uint2 coord, uint face, uint lod = 0) const
                         __intrinsic_asm "$c$0.read(vec<uint,2>(($1).xy), uint(($1).z), uint(($1).w))$z";
                 }
                 break;
             }
-            // TODO: This needs to be handled by the capability system
+            static_assert(false, "Unsupported 'Load' of 'texture' for 'metal' target");
             __intrinsic_asm "<invalid intrinsics>";
         case glsl:
             __intrinsic_asm "$ctexelFetch($0, ($1).$w1b, ($1).$w1e)$z";
@@ -2819,6 +2820,7 @@ extension __TextureImpl<T,Shape,isArray,0,sampleCount,$(access),isShadow, 0,form
                         __intrinsic_asm "$c$0.read(vec<uint,3>(($1).xyz))$z";
                     break;
                 case $(SLANG_TEXTURE_CUBE):
+                    static_assert(isArray == 0, "Unsupported 'Load' of 'texture cube array' for 'metal' target");
                     if (isShadow == 1)
                     {
                         if (isArray == 1)
@@ -2839,7 +2841,7 @@ extension __TextureImpl<T,Shape,isArray,0,sampleCount,$(access),isShadow, 0,form
                     }
                     break;
                 }
-                // TODO: This needs to be handled by the capability system
+                static_assert(false, "Unsupported 'Load' of 'texture' for 'metal' target");
                 __intrinsic_asm "<invalid intrinsics>";
         }
     }
@@ -2960,10 +2962,10 @@ extension __TextureImpl<T,Shape,isArray,0,sampleCount,$(access),isShadow, 0,form
                         // lod is not supported for 1D texture
                         if (isArray == 1)
                             // void write(Tv color, uint coord, uint array, uint lod = 0) const
-                            __intrinsic_asm "$0.write($2, uint(($1).x))";
+                            __intrinsic_asm "$0.write($2, uint(($1).x), uint(($1).y))";
                         else
                             // void write(Tv color, uint coord, uint lod = 0) const
-                            __intrinsic_asm "$0.write($2, uint(($1).x))";
+                            __intrinsic_asm "$0.write($2, uint($1))";
                         break;
                     case $(SLANG_TEXTURE_2D):
                         if (isShadow == 1)
@@ -2991,23 +2993,16 @@ extension __TextureImpl<T,Shape,isArray,0,sampleCount,$(access),isShadow, 0,form
                             __intrinsic_asm "$0.write($2, vec<uint,3>(($1).xyz))";
                         break;
                     case $(SLANG_TEXTURE_CUBE):
+                        static_assert(isArray == 0, "Unsupported 'Store' of 'texture cube array' for 'metal' target");
                         if (isShadow == 1)
                         {
-                            if (isArray == 1)
-                                // void write(Tv color, uint2 coord, uint face, uint array, uint lod = 0) const
-                                __intrinsic_asm "$0.write($2, vec<uint,2>(($1).xy), uint(($1).z)%6, uint(($1).z)/6)";
-                            else
-                                // void write(Tv color, uint2 coord, uint face, uint lod = 0) const
-                                __intrinsic_asm "$0.write($2, vec<uint,2>(($1).xy), uint(($1).z))";
+                            // void write(Tv color, uint2 coord, uint face, uint lod = 0) const
+                            __intrinsic_asm "$0.write($2, vec<uint,2>(($1).xy), uint(($1).z), uint(($1).w))";
                         }
                         else
                         {
-                            if (isArray == 1)
-                                // void write(Tv color, uint2 coord, uint face, uint array, uint lod = 0) const
-                                __intrinsic_asm "$0.write($2, vec<uint,2>(($1).xy), uint(($1).z)%6, uint(($1).z)/6)";
-                            else
-                                // void write(Tv color, uint2 coord, uint face, uint lod = 0) const
-                                __intrinsic_asm "$0.write($2, vec<uint,2>(($1).xy), uint(($1).z))";
+                            // void write(Tv color, uint2 coord, uint face, uint lod = 0) const
+                            __intrinsic_asm "$0.write($2, vec<uint,2>(($1).xy), uint(($1).z), uint(($1).w))";
                         }
                         break;
                     }