Implement SampleCmpBias and SampleCmpGrad

-these are new for HLSL shader model 6.8
-also change glsl.meta.slang to use existing sampler typealias in hlsl.meta.slang

fixes #8929

Author: davli-nv

docs/command-line-slangc-reference.md

@@ -1541,6 +1541,7 @@ A capability describes an optional feature that a target may or may not support.
 * `texture_querylod` 
 * `texture_querylevels` 
 * `texture_shadowlod` 
+* `texture_shadowgrad` 
 * `atomic_glsl_float1` 
 * `atomic_glsl_float2` 
 * `atomic_glsl_halfvec` 

docs/user-guide/a3-02-reference-capability-atoms.md

@@ -1327,6 +1327,10 @@ Compound Capabilities
 `texture_querylod`
 > Capabilities required to query texture LOD info
 
+`texture_shadowgrad`
+> Capabilities required for shadow texture sampling with bias and gradients.
+> New in HLSL SM6.8 but existed in older GLSL and SPIRV targets.
+
 `texture_shadowlod`
 > Capabilities required to query shadow texture lod info
 

source/slang/glsl.meta.slang

@@ -1327,44 +1327,9 @@ public typealias usamplerCube = SamplerCube<uint4>;
 public typealias isamplerCube = SamplerCube<int4>;
 public typealias samplerCube = SamplerCube<float4>;
 
-__generic<let sampleCount:int=0, let format:int=0>
-public typealias sampler1DShadow = _Texture<
-    float,
-    __Shape1D,
-    0, // isArray
-    0, // isMS
-    sampleCount,
-    0, // access
-    1, // isShadow
-    1, // isCombined
-    format
->;
-
-__generic<let sampleCount:int=0, let format:int=0>
-public typealias sampler2DShadow = _Texture<
-    float,
-    __Shape2D,
-    0, // isArray
-    0, // isMS
-    sampleCount,
-    0, // access
-    1, // isShadow
-    1, // isCombined
-    format
->;
-
-__generic<let sampleCount:int=0, let format:int=0>
-public typealias samplerCubeShadow = _Texture<
-    float,
-    __ShapeCube,
-    0, // isArray
-    0, // isMS
-    sampleCount,
-    0, // access
-    1, // isShadow
-    1, // isCombined
-    format
->;
+public typealias sampler1DShadow = Sampler1DShadow;
+public typealias sampler2DShadow = Sampler2DShadow;
+public typealias samplerCubeShadow = SamplerCubeShadow;
 
 public typealias usampler1DArray = Sampler1DArray<uint4>;
 public typealias isampler1DArray = Sampler1DArray<int4>;
@@ -1378,44 +1343,9 @@ public typealias usamplerCubeArray = SamplerCubeArray<uint4>;
 public typealias isamplerCubeArray = SamplerCubeArray<int4>;
 public typealias samplerCubeArray = SamplerCubeArray<float4>;
 
-__generic<let sampleCount:int=0, let format:int=0>
-public typealias sampler1DArrayShadow = _Texture<
-    float,
-    __Shape1D,
-    1, // isArray
-    0, // isMS
-    sampleCount,
-    0, // access
-    1, // isShadow
-    1, // isCombined
-    format
->;
-
-__generic<let sampleCount:int=0, let format:int=0>
-public typealias sampler2DArrayShadow = _Texture<
-    float,
-    __Shape2D,
-    1, // isArray
-    0, // isMS
-    sampleCount,
-    0, // access
-    1, // isShadow
-    1, // isCombined
-    format
->;
-
-__generic<let sampleCount:int=0, let format:int=0>
-public typealias samplerCubeArrayShadow = _Texture<
-    float,
-    __ShapeCube,
-    1, // isArray
-    0, // isMS
-    sampleCount,
-    0, // access
-    1, // isShadow
-    1, // isCombined
-    format
->;
+public typealias sampler1DArrayShadow = Sampler1DArrayShadow;
+public typealias sampler2DArrayShadow = Sampler2DArrayShadow;
+public typealias samplerCubeArrayShadow = SamplerCubeArrayShadow;
 
 public typealias sampler2DMS = Sampler2DMS<float4>;
 public typealias isampler2DMS = Sampler2DMS<int4>;