Add GLSL Compatibility. (#3321)

* Parse glsl buffer blocks to GLSLInterfaceBlockDecl

* Parse glsl local size layout declarations

* Parse (and ignore) glsl version directives

* spelling

* Better l-value interpretation for glsl interface blocks

* Better l-value interpretation for glsl interface blocks

* Add compile flag for enabling glsl

* Parse and ignore precision modifiers.

* Automatically import `glsl` module for compatiblity.

* Complete vector and matrix types for glsl

* Remove generated file from repo

* Bump .gitignore

* do not mark out globals as params

* Synthesize entrypoint layout from global inout vars.

* update test result.

* Allow HLSL semantic on global variables.

* Fix.

* Fix test.

* Fix win32 compile error.

* Add more builtin input/output and texture intrinsics.

* Add struct/array constructor syntax.

* Skip `#extension` lines.

* overide operator * for matrix/vector multiplication.

* Add `matrixCompMult`.

* Parse modifiers in for loop init var declr.

* Add more glsl intrinsics, add stage into to var layout.

* Allow `int[3] x` syntax.

* Fix array type syntax.

---------

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>
Co-authored-by: Yong He <yhe@nvidia.com>

26 files changed, 1092 insertions, 65 deletions

diff --git a/source/slang/core.meta.slang b/source/slang/core.meta.slang
index 4dff9888d..b1437670e 100644
--- a/source/slang/core.meta.slang
+++ b/source/slang/core.meta.slang
@@ -1482,9 +1482,14 @@ for(auto& prefixInfo : kTexturePrefixes)
 for(auto& shapeInfo : kBaseTextureShapes)
 for(int isArray = 0; isArray < 2; ++isArray)
 for(int isMultisample = 0; isMultisample < 2; ++isMultisample)
+for(int isShadow = 0; isShadow < 2; ++isShadow)
 for(auto& accessInfo : kBaseTextureAccessLevels)
 {
-    TextureTypeInfo info(prefixInfo, shapeInfo, isArray, isMultisample, accessInfo, sb, path);
+    // Define `Shadow` flavored types only for combined texture-samplers.
+    if (!prefixInfo.combined && isShadow == 1)
+        continue;
+
+    TextureTypeInfo info(prefixInfo, shapeInfo, isArray, isMultisample, isShadow, accessInfo, sb, path);
     info.emitTypeDecl();
 }
 
diff --git a/source/slang/glsl.meta.slang b/source/slang/glsl.meta.slang
new file mode 100644
index 000000000..a9518f914
--- /dev/null
+++ b/source/slang/glsl.meta.slang
@@ -0,0 +1,449 @@
+//
+// From the GLSL spec, section 4.1. 'asic Types'
+//
+
+typealias vec2 = vector<float, 2>;
+typealias vec3 = vector<float, 3>;
+typealias vec4 = vector<float, 4>;
+
+typealias dvec2 = vector<double, 2>;
+typealias dvec3 = vector<double, 3>;
+typealias dvec4 = vector<double, 4>;
+
+typealias bvec2 = vector<bool, 2>;
+typealias bvec3 = vector<bool, 3>;
+typealias bvec4 = vector<bool, 4>;
+
+typealias ivec2 = vector<int, 2>;
+typealias ivec3 = vector<int, 3>;
+typealias ivec4 = vector<int, 4>;
+
+typealias uvec2 = vector<uint, 2>;
+typealias uvec3 = vector<uint, 3>;
+typealias uvec4 = vector<uint, 4>;
+
+typealias i8vec2 = vector<int8_t, 2>;
+typealias i8vec3 = vector<int8_t, 3>;
+typealias i8vec4 = vector<int8_t, 4>;
+
+typealias u8vec2 = vector<uint8_t, 2>;
+typealias u8vec3 = vector<uint8_t, 3>;
+typealias u8vec4 = vector<uint8_t, 4>;
+
+typealias i16vec2 = vector<int16_t, 2>;
+typealias i16vec3 = vector<int16_t, 3>;
+typealias i16vec4 = vector<int16_t, 4>;
+
+typealias u16vec2 = vector<uint16_t, 2>;
+typealias u16vec3 = vector<uint16_t, 3>;
+typealias u16vec4 = vector<uint16_t, 4>;
+
+typealias i64vec2 = vector<int64_t, 2>;
+typealias i64vec3 = vector<int64_t, 3>;
+typealias i64vec4 = vector<int64_t, 4>;
+
+typealias u64vec2 = vector<uint64_t, 2>;
+typealias u64vec3 = vector<uint64_t, 3>;
+typealias u64vec4 = vector<uint64_t, 4>;
+
+typealias mat2 = matrix<float, 2, 2>;
+typealias mat3 = matrix<float, 3, 3>;
+typealias mat4 = matrix<float, 4, 4>;
+
+typealias mat2x2 = matrix<float, 2, 2>;
+typealias mat2x3 = matrix<float, 3, 2>;
+typealias mat2x4 = matrix<float, 4, 2>;
+
+typealias mat3x2 = matrix<float, 2, 3>;
+typealias mat3x3 = matrix<float, 3, 3>;
+typealias mat3x4 = matrix<float, 4, 3>;
+
+typealias mat4x2 = matrix<float, 2, 4>;
+typealias mat4x3 = matrix<float, 3, 4>;
+typealias mat4x4 = matrix<float, 4, 4>;
+
+typealias dmat2 = matrix<double, 2, 2>;
+typealias dmat3 = matrix<double, 3, 3>;
+typealias dmat4 = matrix<double, 4, 4>;
+
+typealias dmat2x2 = matrix<double, 2, 2>;
+typealias dmat2x3 = matrix<double, 3, 2>;
+typealias dmat2x4 = matrix<double, 4, 2>;
+
+typealias dmat3x2 = matrix<double, 2, 3>;
+typealias dmat3x3 = matrix<double, 3, 3>;
+typealias dmat3x4 = matrix<double, 4, 3>;
+
+typealias dmat4x2 = matrix<double, 2, 4>;
+typealias dmat4x3 = matrix<double, 3, 4>;
+typealias dmat4x4 = matrix<double, 4, 4>;
+
+typealias usampler1D = Sampler1D<uint4>;
+typealias isampler1D = Sampler1D<int4>;
+typealias sampler1D = Sampler1D<float4>;
+
+typealias usampler2D = Sampler2D<uint4>;
+typealias isampler2D = Sampler2D<int4>;
+typealias sampler2D = Sampler2D<float4>;
+
+typealias usampler3D = Sampler3D<uint4>;
+typealias isampler3D = Sampler3D<int4>;
+typealias sampler3D = Sampler3D<float4>;
+
+typealias usamplerCube = SamplerCube<uint4>;
+typealias isamplerCube = SamplerCube<int4>;
+typealias samplerCube = SamplerCube<float4>;
+
+typealias usampler1DShadow = Sampler1DShadow<uint4>;
+typealias isampler1DShadow = Sampler1DShadow<int4>;
+typealias sampler1DShadow = Sampler1DShadow<float4>;
+
+typealias usampler2DShadow = Sampler2DShadow<uint4>;
+typealias isampler2DShadow = Sampler2DShadow<int4>;
+typealias sampler2DShadow = Sampler2DShadow<float4>;
+
+typealias usamplerCubeShadow = SamplerCubeShadow<uint4>;
+typealias isamplerCubeShadow = SamplerCubeShadow<int4>;
+typealias samplerCubeShadow = SamplerCubeShadow<float4>;
+
+typealias usampler1DArray = Sampler1DArray<uint4>;
+typealias isampler1DArray = Sampler1DArray<int4>;
+typealias sampler1DArray = Sampler1DArray<float4>;
+
+typealias usampler2DArray = Sampler2DArray<uint4>;
+typealias isampler2DArray = Sampler2DArray<int4>;
+typealias sampler2DArray = Sampler2DArray<float4>;
+
+typealias usamplerCubeArray = SamplerCubeArray<uint4>;
+typealias isamplerCubeArray = SamplerCubeArray<int4>;
+typealias samplerCubeArray = SamplerCubeArray<float4>;
+
+typealias usampler1DArrayShadow = Sampler1DArrayShadow<uint4>;
+typealias isampler1DArrayShadow = Sampler1DArrayShadow<int4>;
+typealias sampler1DArrayShadow = Sampler1DArrayShadow<float4>;
+
+typealias usampler2DArrayShadow = Sampler2DArrayShadow<uint4>;
+typealias isampler2DArrayShadow = Sampler2DArrayShadow<int4>;
+typealias sampler2DArrayShadow = Sampler2DArrayShadow<float4>;
+
+typealias usamplerCubeArrayShadow = SamplerCubeArrayShadow<uint4>;
+typealias isamplerCubeArrayShadow = SamplerCubeArrayShadow<int4>;
+typealias samplerCubeArrayShadow = SamplerCubeArrayShadow<float4>;
+
+__intrinsic_op(vectorReshape)
+vector<T,N> __vectorReshape<let N : int, T, let M : int>(vector<T,M> vin);
+
+[ForceInline]
+vector<T,4> texelFetch<T:__BuiltinArithmeticType, let N : int> (Sampler1D<vector<T,N>> sampler, int p, int lod)
+{
+    return __vectorReshape<4>(sampler.Load(int2(p, lod)));
+}
+
+[ForceInline]
+vector<T,4> texelFetch<T:__BuiltinArithmeticType, let N : int> (Sampler2D<vector<T,N>> sampler, ivec2 p, int lod)
+{
+    return __vectorReshape<4>(sampler.Load(int3(p, lod)));
+}
+
+[ForceInline]
+vector<T,4> texelFetch<T:__BuiltinArithmeticType, let N : int> (Sampler3D<vector<T,N>> sampler, ivec3 p, int lod)
+{
+    return __vectorReshape<4>(sampler.Load(int4(p, lod)));
+}
+
+[ForceInline]
+vector<T,4> texelFetch<T:__BuiltinArithmeticType, let N : int> (Sampler1DArray<vector<T,N>> sampler, ivec2 p, int lod)
+{
+    return __vectorReshape<4>(sampler.Load(int3(p, lod)));
+}
+
+[ForceInline]
+vector<T,4> texelFetch<T:__BuiltinArithmeticType, let N : int> (Sampler2DArray<vector<T,N>> sampler, ivec3 p, int lod)
+{
+    return __vectorReshape<4>(sampler.Load(int4(p, lod)));
+}
+
+[ForceInline]
+vector<T,4> texture<T:__BuiltinArithmeticType, let N : int> (Sampler1D<vector<T,N>> sampler, float p, float bias = 0.0)
+{
+    return __vectorReshape<4>(sampler.SampleBias(p, bias));
+}
+
+[ForceInline]
+vector<T,4> texture<T:__BuiltinArithmeticType, let N : int> (Sampler2D<vector<T,N>> sampler, float2 p, float bias = 0.0)
+{
+    return __vectorReshape<4>(sampler.SampleBias(p, bias));
+}
+
+[ForceInline]
+vector<T,4> texture<T:__BuiltinArithmeticType, let N : int> (Sampler3D<vector<T,N>> sampler, float3 p, float bias = 0.0)
+{
+    return __vectorReshape<4>(sampler.SampleBias(p, bias));
+}
+
+[ForceInline]
+vector<T,4> texture<T:__BuiltinArithmeticType, let N : int> (SamplerCube<vector<T,N>> sampler, float3 p, float bias = 0.0)
+{
+    return __vectorReshape<4>(sampler.SampleBias(p, bias));
+}
+
+[ForceInline]
+float texture<T:__BuiltinArithmeticType, let N : int> (Sampler1DShadow<vector<T,N>> sampler, float2 p)
+{
+    return sampler.SampleCmp(p.x, p.y);
+}
+
+[ForceInline]
+float texture<T:__BuiltinArithmeticType, let N : int> (Sampler2DShadow<vector<T,N>> sampler, float3 p)
+{
+    return sampler.SampleCmp(p.xy, p.z);
+}
+
+[ForceInline]
+float texture<T:__BuiltinArithmeticType, let N : int> (SamplerCubeShadow<vector<T,N>> sampler, float4 p)
+{
+    return sampler.SampleCmp(p.xyz, p.w);
+}
+
+[ForceInline]
+vector<T,4> texture<T:__BuiltinArithmeticType, let N : int> (Sampler1DArray<vector<T,N>> sampler, float2 p, float bias = 0.0)
+{
+    return __vectorReshape<4>(sampler.SampleBias(p, bias));
+}
+
+[ForceInline]
+vector<T,4> texture<T:__BuiltinArithmeticType, let N : int> (Sampler2DArray<vector<T,N>> sampler, float3 p, float bias = 0.0)
+{
+    return __vectorReshape<4>(sampler.SampleBias(p, bias));
+}
+
+[ForceInline]
+vector<T,4> texture<T:__BuiltinArithmeticType, let N : int> (SamplerCubeArray<vector<T,N>> sampler, float4 p, float bias = 0.0)
+{
+    return __vectorReshape<4>(sampler.SampleBias(p, bias));
+}
+
+[ForceInline]
+float texture<T:__BuiltinArithmeticType, let N : int> (Sampler1DArrayShadow<vector<T,N>> sampler, float3 p)
+{
+    return sampler.SampleCmp(p.xy, p.z);
+}
+
+[ForceInline]
+float texture<T:__BuiltinArithmeticType, let N : int> (Sampler2DArrayShadow<vector<T,N>> sampler, float4 p)
+{
+    return sampler.SampleCmp(p.xyz, p.w);
+}
+
+// TODO: define `texture` for SamplerCubeArrayShadow.
+
+
+vector<T,4> textureGrad<T:__BuiltinArithmeticType, let N : int> (Sampler1D<vector<T,N>> sampler, float P, float dPdx, float dPdy)
+{
+    return __vectorReshape<4>(sampler.SampleGrad(P, dPdx, dPdy));
+}
+
+vector<T,4> textureGrad<T:__BuiltinArithmeticType, let N : int> (Sampler2D<vector<T,N>> sampler, vec2 P, vec2 dPdx, vec2 dPdy)
+{
+    return __vectorReshape<4>(sampler.SampleGrad(P, dPdx, dPdy));
+}
+
+vector<T,4> textureGrad<T:__BuiltinArithmeticType, let N : int> (Sampler3D<vector<T,N>> sampler, vec3 P, vec3 dPdx, vec3 dPdy)
+{
+    return __vectorReshape<4>(sampler.SampleGrad(P, dPdx, dPdy));
+}
+
+vector<T,4> textureGrad<T:__BuiltinArithmeticType, let N : int> (SamplerCube<vector<T,N>> sampler, vec3 P, vec3 dPdx, vec3 dPdy)
+{
+    return __vectorReshape<4>(sampler.SampleGrad(P, dPdx, dPdy));
+}
+
+vector<T,4> textureGrad<T:__BuiltinArithmeticType, let N : int> (Sampler1DArray<vector<T,N>> sampler, vec2 P, float dPdx, float dPdy)
+{
+    return __vectorReshape<4>(sampler.SampleGrad(P, dPdx, dPdy));
+}
+
+vector<T,4> textureGrad<T:__BuiltinArithmeticType, let N : int> (Sampler2DArray<vector<T,N>> sampler, vec3 P, vec2 dPdx, vec2 dPdy)
+{
+    return __vectorReshape<4>(sampler.SampleGrad(P, dPdx, dPdy));
+}
+
+vector<T,4> textureGrad<T:__BuiltinArithmeticType, let N : int> (SamplerCubeArray<vector<T,N>> sampler, vec4 P, vec3 dPdx, vec3 dPdy)
+{
+    return __vectorReshape<4>(sampler.SampleGrad(P, dPdx, dPdy));
+}
+
+
+out float4 gl_Position : SV_Position;
+out float gl_PointSize : SV_PointSize;
+in vec4 gl_FragCoord : SV_Position;
+out float gl_FragDepth : SV_Depth;
+out int gl_FragStencilRef : SV_StencilRef;
+
+in uvec3 gl_GlobalInvocationID : SV_DispatchThreadID;
+in uvec3 gl_WorkGroupID : SV_GroupID;
+in uvec3 gl_LocalInvocationIndex : SV_GroupIndex;
+in uvec3 gl_LocalInvocationID : SV_GroupThreadID;
+
+// TODO: define overload for tessellation control stage.
+in int gl_InvocationID : SV_GSInstanceID;
+
+in int gl_InstanceIndex : SV_InstanceID;
+in bool gl_FrontFacing : SV_IsFrontFace;
+
+// TODO: define overload for geometry stage.
+in int gl_Layer : SV_RenderTargetArrayIndex;
+
+in int gl_SampleID : SV_SampleIndex;
+in int gl_VertexIndex : SV_VertexID;
+in int gl_ViewIndex : SV_ViewID;
+in int gl_ViewportIndex : SV_ViewportArrayIndex;
+
+
+// Override operator* behavior to compute algebric product of matrices and vectors.
+
+[OverloadRank(15)]
+[ForceInline]
+matrix<float, N, N> operator*<let N : int>(matrix<float, N, N> m1, matrix<float, N, N> m2)
+{
+    return mul(m2, m1);
+}
+
+[OverloadRank(15)]
+[ForceInline]
+matrix<half, N, N> operator*<let N : int>(matrix<half, N, N> m1, matrix<half, N, N> m2)
+{
+    return mul(m2, m1);
+}
+
+[OverloadRank(15)]
+[ForceInline]
+matrix<double, N, N> operator*<let N : int>(matrix<double, N, N> m1, matrix<double, N, N> m2)
+{
+    return mul(m2, m1);
+}
+
+[ForceInline]
+[OverloadRank(15)]
+matrix<T, R, L> operator*<T:__BuiltinFloatingPointType, let L : int, let C : int, let R : int>(matrix<T, C, L> m1, matrix<T, R, C> m2)
+{
+    return mul(m2, m1);
+}
+
+[ForceInline]
+[OverloadRank(15)]
+vector<T, R> operator*<T:__BuiltinFloatingPointType, let C : int, let R : int>(vector<T, C> v, matrix<T, R, C> m)
+{
+    return mul(m, v);
+}
+
+[ForceInline]
+[OverloadRank(15)]
+vector<T, C> operator*<T:__BuiltinFloatingPointType, let C : int, let R : int>(matrix<T, R, C> m, vector<T, R> v)
+{
+    return mul(v, m);
+}
+
+__intrinsic_op(mul)
+matrix<T, N, M> matrixCompMult<T:__BuiltinFloatingPointType, let N : int, let M : int>(matrix<T,N,M> left, matrix<T,N,M> right);
+
+__intrinsic_op(cmpLE)
+vector<bool, N> lessThanEqual<T, let N:int>(vector<T, N> x, vector<T, N> y);
+__intrinsic_op(cmpLT)
+vector<bool, N> lessThan<T, let N:int>(vector<T, N> x, vector<T, N> y);
+__intrinsic_op(cmpGT)
+vector<bool, N> greaterThan<T, let N:int>(vector<T, N> x, vector<T, N> y);
+__intrinsic_op(cmpGE)
+vector<bool, N> greaterThanEqual<T, let N:int>(vector<T, N> x, vector<T, N> y);
+__intrinsic_op(cmpEQ)
+vector<bool, N> equal<T, let N:int>(vector<T, N> x, vector<T, N> y);
+__intrinsic_op(cmpNE)
+vector<bool, N> notEqual<T, let N:int>(vector<T, N> x, vector<T, N> y);
+
+__generic<T>
+extension vector<T, 2>
+{
+    [ForceInline] __init(vector<T, 3> bigger) { this = bigger.xy; }
+    [ForceInline] __init(vector<T, 4> bigger) { this = bigger.xy; }
+}
+
+__generic<T>
+extension vector<T, 3>
+{
+    [ForceInline] __init(vector<T, 4> bigger) { this = bigger.xyz; }
+}
+
+[ForceInline]
+[OverloadRank(15)]
+bool operator==<T:__BuiltinArithmeticType, let N : int>(vector<T, N> left, vector<T, N> right)
+{
+    return all(equal(left, right));
+}
+
+[ForceInline]
+[OverloadRank(15)]
+bool operator!=<T:__BuiltinArithmeticType, let N : int>(vector<T, N> left, vector<T, N> right)
+{
+    return any(notEqual(left, right));
+}
+
+[ForceInline]
+[OverloadRank(14)]
+bool operator==<T:__BuiltinFloatingPointType, let N : int>(vector<T, N> left, vector<T, N> right)
+{
+    return all(equal(left, right));
+}
+
+[ForceInline]
+[OverloadRank(14)]
+bool operator!=<T:__BuiltinFloatingPointType, let N : int>(vector<T, N> left, vector<T, N> right)
+{
+    return any(notEqual(left, right));
+}
+
+[ForceInline]
+[OverloadRank(14)]
+bool operator==<T:__BuiltinLogicalType, let N : int>(vector<T, N> left, vector<T, N> right)
+{
+    return all(equal(left, right));
+}
+
+[ForceInline]
+[OverloadRank(14)]
+bool operator!=<T:__BuiltinLogicalType, let N : int>(vector<T, N> left, vector<T, N> right)
+{
+    return any(notEqual(left, right));
+}
+
+${{{{
+for (auto type : kBaseTypes) {
+    char const* typeName = type.name;
+    if (!type.flags) continue;
+}}}}
+[ForceInline]
+[OverloadRank(15)]
+bool operator==<let N : int>(vector<$(typeName), N> left, vector<$(typeName), N> right)
+{
+    return all(equal(left, right));
+}
+
+[ForceInline]
+[OverloadRank(15)]
+bool operator!=<let N : int>(vector<$(typeName), N> left, vector<$(typeName), N> right)
+{
+    return any(notEqual(left, right));
+}
+${{{{
+}
+}}}}
+
+[ForceInline] int findLSB(int v) { return firstbitlow(v); }
+[ForceInline] uint findLSB(uint v) { return firstbitlow(v); }
+[ForceInline] vector<int,N> findLSB<let N:int>(vector<int,N> value)
+{
+    return firstbitlow(value);
+}
+[ForceInline] vector<uint,N> findLSB<let N:int>(vector<uint,N> value)
+{
+    return firstbitlow(value);
+}
diff --git a/source/slang/hlsl.meta.slang b/source/slang/hlsl.meta.slang
index e29e0c3cc..6520ab1fa 100644
--- a/source/slang/hlsl.meta.slang
+++ b/source/slang/hlsl.meta.slang
@@ -2457,7 +2457,7 @@ T dot(vector<T, N> x, vector<T, N> y)
 
 __generic<T : __BuiltinFloatingPointType> vector<T,4> dst(vector<T,4> x, vector<T,4> y);
 
-// Given a RWByteAddressBuffer allow it to be interpretted as a RWStructuredBuffer
+// Given a RWByteAddressBuffer allow it to be interpreted as a RWStructuredBuffer
 __intrinsic_op($(kIROp_GetEquivalentStructuredBuffer))
 RWStructuredBuffer<T> __getEquivalentStructuredBuffer<T>(RWByteAddressBuffer b);
 
diff --git a/source/slang/slang-ast-decl.h b/source/slang/slang-ast-decl.h
index 553a5c26f..e43141cad 100644
--- a/source/slang/slang-ast-decl.h
+++ b/source/slang/slang-ast-decl.h
@@ -151,6 +151,10 @@ class ClassDecl : public AggTypeDecl
     SLANG_AST_CLASS(ClassDecl)
 };
 
+class GLSLInterfaceBlockDecl : public AggTypeDecl
+{
+    SLANG_AST_CLASS(GLSLInterfaceBlockDecl);
+};
 
 // TODO: Is it appropriate to treat an `enum` as an aggregate type?
 // Most code that looks for, e.g., conformances assumes user-defined
diff --git a/source/slang/slang-ast-modifier.h b/source/slang/slang-ast-modifier.h
index 4288017fa..9ee3fea86 100644
--- a/source/slang/slang-ast-modifier.h
+++ b/source/slang/slang-ast-modifier.h
@@ -30,7 +30,7 @@ class ExportedModifier : public Modifier { SLANG_AST_CLASS(ExportedModifier)};
 class ConstExprModifier : public Modifier { SLANG_AST_CLASS(ConstExprModifier)};
 class GloballyCoherentModifier : public Modifier { SLANG_AST_CLASS(GloballyCoherentModifier)};
 class ExternCppModifier : public Modifier { SLANG_AST_CLASS(ExternCppModifier)};
-
+class GLSLPrecisionModifier : public Modifier { SLANG_AST_CLASS(GLSLPrecisionModifier)};
 
 // Marks that the definition of a decl is not yet synthesized.
 class ToBeSynthesizedModifier : public Modifier {SLANG_AST_CLASS(ToBeSynthesizedModifier)};
@@ -765,6 +765,12 @@ class DisableArrayFlatteningAttribute : public Attribute
     SLANG_AST_CLASS(DisableArrayFlatteningAttribute);
 };
 
+// A GLSL layout(local_size_x = 64, ... attribute)
+class GLSLLayoutLocalSizeAttribute : public Attribute
+{
+    SLANG_AST_CLASS(GLSLLayoutLocalSizeAttribute)
+};
+
 // TODO: for attributes that take arguments, the syntax node
 // classes should provide accessors for the values of those arguments.
 
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 8d7337318..c31c94a85 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -389,6 +389,11 @@ namespace Slang
         //
         if(decl->hasModifier<HLSLStaticModifier>()) return false;
 
+        // While not normally allowed, out variables are not constant
+        // parameters, this can happen for example in GLSL mode
+        if(decl->hasModifier<OutModifier>()) return false;
+        if(decl->hasModifier<InModifier>()) return false;
+
         // The `groupshared` modifier indicates that a variable cannot
         // be a shader parameters, but is instead transient storage
         // allocated for the duration of a thread-group's execution.
@@ -1219,6 +1224,22 @@ namespace Slang
                     varDecl->type.type = m_astBuilder->getConstantBufferType(varDecl->type);
                 }
             }
+
+            if (getLinkage()->getAllowGLSLInput())
+            {
+                // If we are in GLSL compatiblity mode, we want to treat all global variables
+                // without any `uniform` modifiers as true global variables by default.
+                if (!varDecl->findModifier<HLSLUniformModifier>() &&
+                    !varDecl->findModifier<InModifier>() &&
+                    !varDecl->findModifier<OutModifier>())
+                {
+                    if (!as<ResourceType>(varDecl->type) && !as<PointerLikeType>(varDecl->type))
+                    {
+                        auto staticModifier = m_astBuilder->create<HLSLStaticModifier>();
+                        addModifier(varDecl, staticModifier);
+                    }
+                }
+            }
         }
     }
 
diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index 2f8b28afc..e130275bb 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -269,6 +269,25 @@ namespace Slang
         }
     }
 
+    static bool isMutableGLSLBufferBlockVarExpr(Expr* expr)
+    {
+        if(const auto varExpr = as<VarExpr>(expr))
+        {
+            if(const auto declRefType = as<DeclRefType>(varExpr->type->getCanonicalType()))
+            {
+                if(declRefType->getDeclRef().getDecl()->isDerivedFrom(ASTNodeType::GLSLInterfaceBlockDecl))
+                {
+                    const auto d = varExpr->declRef.getDecl();
+                    if(d->hasModifier<GLSLBufferModifier>() && !d->hasModifier<GLSLReadOnlyModifier>())
+                    {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+
     DeclRefExpr* SemanticsVisitor::ConstructDeclRefExpr(
         DeclRef<Decl>   declRef,
         Expr*    baseExpr,
@@ -370,7 +389,10 @@ namespace Slang
                 // l-value status of the base expression into account now.
                 if(!baseExpr->type.isLeftValue)
                 {
-                    expr->type.isLeftValue = false;
+                    // One exception to this is if we're reading the contents
+                    // of a GLSL buffer interface block which isn't marked as
+                    // read_only
+                    expr->type.isLeftValue = isMutableGLSLBufferBlockVarExpr(baseExpr);
                 }
                 else
                 {
diff --git a/source/slang/slang-check-overload.cpp b/source/slang/slang-check-overload.cpp
index 27062fc0c..2d7315cd2 100644
--- a/source/slang/slang-check-overload.cpp
+++ b/source/slang/slang-check-overload.cpp
@@ -2005,13 +2005,25 @@ namespace Slang
                 typeCheckingCache->resolvedOperatorOverloadCache[key] = *context.bestCandidate;
             return CompleteOverloadCandidate(context, *context.bestCandidate);
         }
-        else
+        else if (auto typetype = as<TypeType>(funcExprType))
         {
-            // Nothing at all was found that we could even consider invoking
-            getSink()->diagnose(expr->functionExpr, Diagnostics::expectedFunction, funcExprType);
-            expr->type = QualType(m_astBuilder->getErrorType());
-            return expr;
-        }
+            // We allow a special case when `funcExpr` represents a composite type,
+            // in which case we will try to construct the type via memberwise assignment from the arguments.
+            //
+            auto initListExpr = m_astBuilder->create<InitializerListExpr>();
+            initListExpr->loc = expr->loc;
+            initListExpr->args.addRange(expr->arguments);
+            initListExpr->type = m_astBuilder->getInitializerListType();
+            Expr* outExpr = nullptr;
+            if (_coerceInitializerList(typetype->getType(), &outExpr, initListExpr))
+                return outExpr;
+        }
+
+        // Nothing at all was found that we could even consider invoking.
+        // In all other cases, this is an error.
+        getSink()->diagnose(expr->functionExpr, Diagnostics::expectedFunction, funcExprType);
+        expr->type = QualType(m_astBuilder->getErrorType());
+        return expr;
     }
 
     void SemanticsVisitor::AddGenericOverloadCandidate(
diff --git a/source/slang/slang-compiler.h b/source/slang/slang-compiler.h
index c3f2d8e70..e8c624b01 100755
--- a/source/slang/slang-compiler.h
+++ b/source/slang/slang-compiler.h
@@ -1812,6 +1812,14 @@ namespace Slang
         {
             m_enableEffectAnnotations = value;
         }
+        bool getAllowGLSLInput()
+        {
+            return m_allowGLSLInput;
+        }
+        void setAllowGLSLInput(bool value)
+        {
+            m_allowGLSLInput = value;
+        }
 
         // Information on the targets we are being asked to
         // generate code for.
@@ -1972,6 +1980,7 @@ namespace Slang
         bool m_requireCacheFileSystem = false;
         bool m_useFalcorCustomSharedKeywordSemantics = false;
         bool m_enableEffectAnnotations = false;
+        bool m_allowGLSLInput = false;
 
         // Modules that have been read in with the -r option
         List<ComPtr<IArtifact>> m_libModules;
@@ -2641,6 +2650,7 @@ namespace Slang
         virtual SLANG_NO_THROW SlangResult SLANG_MCALL setGlobalGenericArgs(int genericArgCount, char const** genericArgs) SLANG_OVERRIDE;
         virtual SLANG_NO_THROW SlangResult SLANG_MCALL setTypeNameForGlobalExistentialTypeParam(int slotIndex, char const* typeName) SLANG_OVERRIDE;
         virtual SLANG_NO_THROW SlangResult SLANG_MCALL setTypeNameForEntryPointExistentialTypeParam(int entryPointIndex, int slotIndex, char const* typeName) SLANG_OVERRIDE;
+        virtual SLANG_NO_THROW void SLANG_MCALL setAllowGLSLInput(bool value) SLANG_OVERRIDE;
         virtual SLANG_NO_THROW SlangResult SLANG_MCALL compile() SLANG_OVERRIDE;
         virtual SLANG_NO_THROW char const* SLANG_MCALL getDiagnosticOutput() SLANG_OVERRIDE;
         virtual SLANG_NO_THROW SlangResult SLANG_MCALL getDiagnosticOutputBlob(ISlangBlob** outBlob) SLANG_OVERRIDE;
@@ -3055,7 +3065,7 @@ namespace Slang
         ComPtr<ISlangBlob> coreLibraryCode;
         //ComPtr<ISlangBlob> slangLibraryCode;
         ComPtr<ISlangBlob> hlslLibraryCode;
-        //ComPtr<ISlangBlob> glslLibraryCode;
+        ComPtr<ISlangBlob> glslLibraryCode;
         ComPtr<ISlangBlob> autodiffLibraryCode;
 
         String  getStdlibPath();
@@ -3063,6 +3073,7 @@ namespace Slang
         ComPtr<ISlangBlob> getCoreLibraryCode();
         ComPtr<ISlangBlob> getHLSLLibraryCode();
         ComPtr<ISlangBlob> getAutodiffLibraryCode();
+        ComPtr<ISlangBlob> getGLSLLibraryCode();
 
         RefPtr<SharedASTBuilder> m_sharedASTBuilder;
 
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 58a2fbf4a..75308c829 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -66,7 +66,7 @@ DIAGNOSTIC(    8, Error, outputPathsImplyDifferentFormats,
     "the output paths '$0' and '$1' require different code-generation targets")
 
 DIAGNOSTIC(    10, Error, explicitOutputPathsAndMultipleTargets, "canot use both explicit output paths ('-o') and multiple targets ('-target')")
-DIAGNOSTIC(    11, Error, glslIsNotSupported, "the Slang compiler does not support GLSL as a source language")
+DIAGNOSTIC(    11, Error, glslIsNotSupported, "the Slang compiler does not support GLSL as a source language by default, please use -allow-glsl")
 DIAGNOSTIC(    12, Error, cannotDeduceSourceLanguage, "can't deduce language for input file '$0'")
 DIAGNOSTIC(    13, Error, unknownCodeGenerationTarget, "unknown code generation target '$0'")
 DIAGNOSTIC(    14, Error, unknownProfile, "unknown profile '$0'")
@@ -173,6 +173,7 @@ DIAGNOSTIC(15202, Error, divideByZeroInPreprocessorExpression, "division by zero
 DIAGNOSTIC(15203, Error, expectedTokenInDefinedExpression, "expected '$0' in 'defined' expression")
 DIAGNOSTIC(15204, Warning, directiveExpectsExpression, "'$0' directive requires an expression")
 DIAGNOSTIC(15205, Warning, undefinedIdentifierInPreprocessorExpression, "undefined identifier '$0' in preprocessor expression will evaluate to zero")
+DIAGNOSTIC(15206, Error, expectedIntegralVersionNumber, "Expected integer for #version number")
 
 DIAGNOSTIC(-1, Note, seeOpeningToken, "see opening '$0'")
 
@@ -741,6 +742,9 @@ DIAGNOSTIC(55102, Error, invalidTorchKernelParamType, "'$0' is not a valid param
 DIAGNOSTIC(56001, Error, unableToAutoMapCUDATypeToHostType, "Could not automatically map '$0' to a host type. Automatic binding generation failed for '$1'")
 
 DIAGNOSTIC(57001, Warning, spirvOptFailed, "spirv-opt failed. $0")
+
+// GLSL Compatibility
+DIAGNOSTIC(58001, Error, entryPointMustReturnVoidWhenGlobalOutputPresent, "entry point must return 'void' when global output variables are present.")
 //
 // 8xxxx - Issues specific to a particular library/technology/platform/etc.
 //
diff --git a/source/slang/slang-emit-glsl.cpp b/source/slang/slang-emit-glsl.cpp
index ccb296e84..4a75e84a0 100644
--- a/source/slang/slang-emit-glsl.cpp
+++ b/source/slang/slang-emit-glsl.cpp
@@ -732,6 +732,10 @@ void GLSLSourceEmitter::_emitGLSLTextureOrTextureSamplerType(IRTextureTypeBase*
     {
         m_writer->emit("Array");
     }
+    if (type->isShadow())
+    {
+        m_writer->emit("Shadow");
+    }
 }
 
 void GLSLSourceEmitter::_emitGLSLTypePrefix(IRType* type, bool promoteHalfToFloat)
diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index ce982a58c..1ee5ba67c 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -64,6 +64,7 @@
 #include "slang-ir-wrap-structured-buffers.h"
 #include "slang-ir-liveness.h"
 #include "slang-ir-glsl-liveness.h"
+#include "slang-ir-translate-glsl-global-var.h"
 #include "slang-ir-legalize-uniform-buffer-load.h"
 #include "slang-ir-lower-buffer-element-type.h"
 #include "slang-ir-string-hash.h"
@@ -231,6 +232,7 @@ Result linkAndOptimizeIR(
     dumpIRIfEnabled(codeGenContext, irModule, "LINKED");
 #endif
 
+
     validateIRModuleIfEnabled(codeGenContext, irModule);
 
     // If the user specified the flag that they want us to dump
@@ -238,6 +240,8 @@ Result linkAndOptimizeIR(
     // un-specialized IR.
     dumpIRIfEnabled(codeGenContext, irModule);
 
+    translateGLSLGlobalVar(codeGenContext, irModule);
+
     // Replace any global constants with their values.
     //
     replaceGlobalConstants(irModule);
diff --git a/source/slang/slang-ir-inst-defs.h b/source/slang/slang-ir-inst-defs.h
index e32f0d084..8f87d23e7 100644
--- a/source/slang/slang-ir-inst-defs.h
+++ b/source/slang/slang-ir-inst-defs.h
@@ -823,6 +823,9 @@ INST(HighLevelDeclDecoration,               highLevelDecl,          1, 0)
         /// A call to the decorated function should always be folded into its use site.
     INST(AlwaysFoldIntoUseSiteDecoration, alwaysFold, 0, 0)
 
+    INST(GlobalOutputDecoration, output, 0, 0)
+    INST(GlobalInputDecoration, output, 0, 0)
+    INST(GLSLLocationDecoration, glslLocation, 1, 0)
     INST(PayloadDecoration, payload, 0, 0)
 
     /* Mesh Shader outputs */
@@ -832,7 +835,6 @@ INST(HighLevelDeclDecoration,               highLevelDecl,          1, 0)
     INST_RANGE(MeshOutputDecoration, VerticesDecoration, PrimitivesDecoration)
     INST(HLSLMeshPayloadDecoration, payload, 0, 0)
     INST(GLSLPrimitivesRateDecoration, perprimitive, 0, 0)
-
         // Marks an inst that represents the gl_Position output.
     INST(GLPositionOutputDecoration, PositionOutput, 0, 0)
 
diff --git a/source/slang/slang-ir-insts.h b/source/slang/slang-ir-insts.h
index a2662d53f..2869f7058 100644
--- a/source/slang/slang-ir-insts.h
+++ b/source/slang/slang-ir-insts.h
@@ -361,6 +361,14 @@ IR_SIMPLE_DECORATION(AlwaysFoldIntoUseSiteDecoration)
 IR_SIMPLE_DECORATION(StaticRequirementDecoration)
 IR_SIMPLE_DECORATION(NonCopyableTypeDecoration)
 IR_SIMPLE_DECORATION(HLSLMeshPayloadDecoration)
+IR_SIMPLE_DECORATION(GlobalInputDecoration)
+IR_SIMPLE_DECORATION(GlobalOutputDecoration)
+
+struct IRGLSLLocationDecoration : IRDecoration
+{
+    IR_LEAF_ISA(GLSLLocationDecoration)
+    IRIntLit* getLocation() { return cast<IRIntLit>(getOperand(0)); }
+};
 
 struct IRNVAPIMagicDecoration : IRDecoration
 {
diff --git a/source/slang/slang-ir-translate-glsl-global-var.cpp b/source/slang/slang-ir-translate-glsl-global-var.cpp
new file mode 100644
index 000000000..41005e9d4
--- /dev/null
+++ b/source/slang/slang-ir-translate-glsl-global-var.cpp
@@ -0,0 +1,211 @@
+#include "slang-ir-translate-glsl-global-var.h"
+
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+#include "slang-ir-util.h"
+
+namespace Slang
+{
+    struct GlobalVarTranslationContext
+    {
+        CodeGenContext* context;
+
+        void processModule(IRModule* module)
+        {
+            List<IRInst*> outputVars;
+            List<IRInst*> inputVars;
+            List<IRInst*> entryPoints;
+            for (auto inst : module->getGlobalInsts())
+            {
+                if (inst->findDecoration<IRGlobalOutputDecoration>())
+                    outputVars.add(inst);
+                if (inst->findDecoration<IRGlobalInputDecoration>())
+                    inputVars.add(inst);
+                if (inst->findDecoration<IREntryPointDecoration>())
+                    entryPoints.add(inst);
+            }
+
+            IRBuilder builder(module);
+
+            bool hasInput = inputVars.getCount() != 0;
+            bool hasOutput = outputVars.getCount() != 0;
+
+            if (!hasInput && !hasOutput)
+                return;
+
+            for (auto entryPoint : entryPoints)
+            {
+                auto entryPointFunc = as<IRFunc>(entryPoint);
+                if (!entryPointFunc)
+                    continue;
+             
+                auto entryPointDecor = entryPointFunc->findDecoration<IREntryPointDecoration>();
+
+                IRVarLayout* resultVarLayout = nullptr;
+                IRVarLayout* paramLayout = nullptr;
+                IRType* resultType = entryPointFunc->getResultType();
+
+                // Create a struct type to receive all inputs.
+                builder.setInsertBefore(entryPointFunc);
+                auto inputStructType = builder.createStructType();
+                IRStructTypeLayout::Builder inputStructTypeLayoutBuilder(&builder);
+                UInt inputVarIndex = 0;
+                List<IRStructKey*> inputKeys;
+                for (auto input : inputVars)
+                {
+                    auto inputType = cast<IRPtrTypeBase>(input->getDataType())->getValueType();
+                    auto key = builder.createStructKey();
+                    inputKeys.add(key);
+                    if (auto nameHint = input->findDecoration<IRNameHintDecoration>())
+                    {
+                        builder.addNameHintDecoration(key, nameHint->getName());
+                    }
+                    builder.createStructField(inputStructType, key, inputType);
+                    IRTypeLayout::Builder fieldTypeLayout(&builder);
+                    fieldTypeLayout.addResourceUsage(LayoutResourceKind::VaryingInput, LayoutSize(1));
+                    IRVarLayout::Builder varLayoutBuilder(&builder, fieldTypeLayout.build());
+                    varLayoutBuilder.setStage(entryPointDecor->getProfile().getStage());
+                    if (auto locationDecoration = input->findDecoration<IRGLSLLocationDecoration>())
+                    {
+                        varLayoutBuilder.findOrAddResourceInfo(LayoutResourceKind::VaryingInput)->offset = (UInt)getIntVal(locationDecoration->getLocation());
+                    }
+                    if (auto semanticDecor = input->findDecoration<IRSemanticDecoration>())
+                    {
+                        varLayoutBuilder.setSystemValueSemantic(semanticDecor->getSemanticName(), semanticDecor->getSemanticIndex());
+                    }
+                    else
+                    {
+                        if (entryPointDecor->getProfile().getStage() == Stage::Fragment)
+                        {
+                            varLayoutBuilder.setUserSemantic("COLOR", inputVarIndex);
+                        }
+                        else if (entryPointDecor->getProfile().getStage() == Stage::Vertex)
+                        {
+                            varLayoutBuilder.setUserSemantic("VERTEX_IN_", inputVarIndex);
+                        }
+                        inputVarIndex++;
+                    }
+                    inputStructTypeLayoutBuilder.addField(key, varLayoutBuilder.build());
+                }
+                auto paramTypeLayout = inputStructTypeLayoutBuilder.build();
+                IRVarLayout::Builder paramVarLayoutBuilder(&builder, paramTypeLayout);
+                paramLayout = paramVarLayoutBuilder.build();
+
+                // Add an entry point parameter for all the inputs.
+                auto firstBlock = entryPointFunc->getFirstBlock();
+                builder.setInsertInto(firstBlock);
+                auto inputParam = builder.emitParam(inputStructType);
+                builder.addLayoutDecoration(inputParam, paramLayout);
+
+                // Initialize all global variables.
+                for (Index i = 0; i < inputVars.getCount(); i++)
+                {
+                    auto input = inputVars[i];
+                    setInsertBeforeOrdinaryInst(&builder, firstBlock->getFirstOrdinaryInst());
+                    auto inputType = cast<IRPtrTypeBase>(input->getDataType())->getValueType();
+                    builder.emitStore(input,
+                        builder.emitFieldExtract(inputType, inputParam, inputKeys[i]));
+                }
+
+                // For each entry point, introduce a new parameter to represent each input parameter,
+                // and return all outputs via a struct value.
+                if (hasOutput)
+                {
+                    // If we have global outputs, the entry-point must not return anything itself.
+                    if (as<IRFuncType>(entryPoint->getDataType())->getResultType()->getOp() != kIROp_VoidType)
+                    {
+                        context->getSink()->diagnose(entryPointFunc, Diagnostics::entryPointMustReturnVoidWhenGlobalOutputPresent);
+                        continue;
+                    }
+                    builder.setInsertBefore(entryPointFunc);
+                    resultType = builder.createStructType();
+                    IRStructTypeLayout::Builder typeLayoutBuilder(&builder);
+                    UInt outputVarIndex = 0;
+                    for (auto output : outputVars)
+                    {
+                        auto key = builder.createStructKey();
+                        if (auto nameHint = output->findDecoration<IRNameHintDecoration>())
+                        {
+                            builder.addNameHintDecoration(key, nameHint->getName());
+                        }
+                        auto ptrType = as<IRPtrTypeBase>(output->getDataType());
+                        builder.createStructField(resultType, key, ptrType->getValueType());
+                        IRTypeLayout::Builder fieldTypeLayout(&builder);
+                        fieldTypeLayout.addResourceUsage(LayoutResourceKind::VaryingOutput, LayoutSize(1));
+                        IRVarLayout::Builder varLayoutBuilder(&builder, fieldTypeLayout.build());
+                        varLayoutBuilder.setStage(entryPointDecor->getProfile().getStage());
+                        if (auto semanticDecor = output->findDecoration<IRSemanticDecoration>())
+                        {
+                            varLayoutBuilder.setSystemValueSemantic(semanticDecor->getSemanticName(), semanticDecor->getSemanticIndex());
+                        }
+                        else
+                        {
+                            if (auto locationDecoration = output->findDecoration<IRGLSLLocationDecoration>())
+                            {
+                                varLayoutBuilder.findOrAddResourceInfo(LayoutResourceKind::VaryingOutput)->offset = (UInt)getIntVal(locationDecoration->getLocation());
+                            }
+                            if (entryPointDecor->getProfile().getStage() == Stage::Fragment)
+                            {
+                                varLayoutBuilder.setSystemValueSemantic("SV_TARGET", outputVarIndex);
+                            }
+                            else if (entryPointDecor->getProfile().getStage() == Stage::Vertex)
+                            {
+                                varLayoutBuilder.setUserSemantic("COLOR", outputVarIndex);
+                            }
+                            outputVarIndex++;
+                        }
+                        typeLayoutBuilder.addField(key, varLayoutBuilder.build());
+                    }
+                    auto resultTypeLayout = typeLayoutBuilder.build();
+                    IRVarLayout::Builder resultVarLayoutBuilder(&builder, resultTypeLayout);
+                    resultVarLayout = resultVarLayoutBuilder.build();
+                    
+                    for (auto block : entryPointFunc->getBlocks())
+                    {
+                        if (auto returnInst = as<IRReturn>(block->getTerminator()))
+                        {
+                            // Return the struct value.
+                            builder.setInsertBefore(returnInst);
+                            List<IRInst*> fieldVals;
+                            for (auto outputVar : outputVars)
+                            {
+                                auto load = builder.emitLoad(outputVar);
+                                fieldVals.add(load);
+                            }
+                            auto resultVal = builder.emitMakeStruct(resultType, (UInt)fieldVals.getCount(), fieldVals.getBuffer());
+                            builder.emitReturn(resultVal);
+                            returnInst->removeAndDeallocate();
+                        }
+                    }
+                }
+                if (auto entryPointLayoutDecor = entryPointFunc->findDecoration<IRLayoutDecoration>())
+                {
+                    if (auto entryPointLayout = as<IREntryPointLayout>(entryPointLayoutDecor->getLayout()))
+                    {
+                        if (paramLayout)
+                            builder.replaceOperand(entryPointLayout->getOperands(), paramLayout);
+                        if (resultVarLayout)
+                            builder.replaceOperand(entryPointLayout->getOperands() + 1, resultVarLayout);
+                    }
+
+                }
+                // Update func type for the entry point.
+                List<IRType*> paramTypes;
+                for (auto param : entryPointFunc->getParams())
+                {
+                    paramTypes.add(param->getDataType());
+                }
+                IRType* newFuncType = builder.getFuncType(paramTypes, resultType);
+                entryPointFunc->setFullType(newFuncType);
+            }
+        }
+    };
+
+    void translateGLSLGlobalVar(CodeGenContext* context, IRModule* module)
+    {
+        
+        GlobalVarTranslationContext ctx;
+        ctx.context = context;
+        ctx.processModule(module);
+    }
+}
diff --git a/source/slang/slang-ir-translate-glsl-global-var.h b/source/slang/slang-ir-translate-glsl-global-var.h
new file mode 100644
index 000000000..f22b6c028
--- /dev/null
+++ b/source/slang/slang-ir-translate-glsl-global-var.h
@@ -0,0 +1,17 @@
+// slang-ir-translate-glsl-global-var.h
+#ifndef SLANG_IR_TRANSLATE_GLSL_GLOBAL_VAR_H
+#define SLANG_IR_TRANSLATE_GLSL_GLOBAL_VAR_H
+
+namespace Slang
+{
+
+    struct IRModule;
+    struct CodeGenContext;
+
+    /// Translate global in/out variables defined in GLSL-flavored code
+    /// into entry point parameters with system value semantics.
+    void translateGLSLGlobalVar(CodeGenContext* context, IRModule* module);
+
+}
+
+#endif // SLANG_IR_TRANSLATE_GLSL_GLOBAL_VAR_H
diff --git a/source/slang/slang-ir.h b/source/slang/slang-ir.h
index 8d7cad0b4..f0be72248 100644
--- a/source/slang/slang-ir.h
+++ b/source/slang/slang-ir.h
@@ -1378,6 +1378,7 @@ struct IRResourceTypeBase : IRType
     bool isFeedback() const { return getFlavor().isFeedback(); }
     bool isMultisample() const { return getFlavor().isMultisample(); }
     bool isArray() const { return getFlavor().isArray(); }
+    bool isShadow() const { return getFlavor().isShadow(); }
     SlangResourceShape getShape() const { return getFlavor().getShape(); }
     SlangResourceAccess getAccess() const { return getFlavor().getAccess(); }
 
diff --git a/source/slang/slang-lower-to-ir.cpp b/source/slang/slang-lower-to-ir.cpp
index b2c0dbb18..38651c5a4 100644
--- a/source/slang/slang-lower-to-ir.cpp
+++ b/source/slang/slang-lower-to-ir.cpp
@@ -30,7 +30,6 @@
 #include "slang-ir-obfuscate-loc.h"
 #include "slang-ir-use-uninitialized-out-param.h"
 #include "slang-ir-peephole.h"
-
 #include "slang-mangle.h"
 #include "slang-type-layout.h"
 #include "slang-visitor.h"
@@ -2155,7 +2154,23 @@ void addVarDecorations(
         {
             builder->addSimpleDecoration<IRHLSLMeshPayloadDecoration>(inst);
         }
-
+        else if (as<OutModifier>(mod))
+        {
+            builder->addSimpleDecoration<IRGlobalOutputDecoration>(inst);
+        }
+        else if (as<InModifier>(mod))
+        {
+            builder->addSimpleDecoration<IRGlobalInputDecoration>(inst);
+        }
+        else if (auto glslLocationMod = as<GLSLLocationLayoutModifier>(mod))
+        {
+            builder->addDecoration(inst, kIROp_GLSLLocationDecoration,
+                builder->getIntValue(builder->getIntType(), stringToInt(glslLocationMod->valToken.getContent())));
+        }
+        else if (auto hlslSemantic = as< HLSLSimpleSemantic>(mod))
+        {
+            builder->addSemanticDecoration(inst, hlslSemantic->name.getContent());
+        }
         // TODO: what are other modifiers we need to propagate through?
     }
     if(auto t = composeGetters<IRMeshOutputType>(inst->getFullType(), &IROutTypeBase::getValueType))
@@ -8024,6 +8039,10 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
         {
             irAggType = subBuilder->createClassType();
         }
+        else if (as<GLSLInterfaceBlockDecl>(decl))
+        {
+            return LoweredValInfo();
+        }
         else
         {
             getSink()->diagnose(decl->loc, Diagnostics::unimplemented, "lower unknown AggType to IR");
diff --git a/source/slang/slang-options.cpp b/source/slang/slang-options.cpp
index 67f95df1e..1c1ad8f1c 100644
--- a/source/slang/slang-options.cpp
+++ b/source/slang/slang-options.cpp
@@ -141,6 +141,7 @@ enum class OptionKind
     FileSystem,
     Heterogeneous,
     NoMangle,
+    AllowGLSL,
 
     // Internal
 
@@ -621,7 +622,8 @@ void initCommandOptions(CommandOptions& options)
         { OptionKind::FileSystem, "-file-system", "-file-system <file-system-type>", 
         "Set the filesystem hook to use for a compile request."},
         { OptionKind::Heterogeneous, "-heterogeneous", nullptr, "Output heterogeneity-related code." },
-        { OptionKind::NoMangle, "-no-mangle", nullptr, "Do as little mangling of names as possible." }
+        { OptionKind::NoMangle, "-no-mangle", nullptr, "Do as little mangling of names as possible." },
+        { OptionKind::AllowGLSL, "-allow-glsl", nullptr, "Enable GLSL as an input language." },
     };
     _addOptions(makeConstArrayView(experimentalOpts), options);
 
@@ -912,6 +914,8 @@ struct OptionsParser
 
     String m_spirvCoreGrammarJSONPath;
 
+    bool m_allowGLSLInput = false;
+
     CommandLineReader m_reader;
 
     CommandOptionsWriter::Style m_helpStyle = CommandOptionsWriter::Style::Text;
@@ -1812,6 +1816,7 @@ SlangResult OptionsParser::_parse(
         switch (optionKind)
         {
             case OptionKind::NoMangle: m_flags |= SLANG_COMPILE_FLAG_NO_MANGLING; break;
+            case OptionKind::AllowGLSL: m_allowGLSLInput = true; break;
             case OptionKind::EmitIr: m_requestImpl->m_emitIr = true; break;
             case OptionKind::LoadStdLib:
             {
@@ -2152,7 +2157,7 @@ SlangResult OptionsParser::_parse(
                 m_compileRequest->setEnableEffectAnnotations(true);
                 break;
             }
-            
+
             case OptionKind::EntryPointName:
             {
                 CommandLineArg name;
@@ -2482,6 +2487,8 @@ SlangResult OptionsParser::_parse(
 
     m_compileRequest->setCompileFlags(m_flags);
 
+    m_compileRequest->setAllowGLSLInput(m_allowGLSLInput);
+
     // As a compatability feature, if the user didn't list any explicit entry
     // point names, *and* they are compiling a single translation unit, *and* they
     // have either specified a stage, or we can assume one from the naming
diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index 8c9604df6..0a2076fd0 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -82,6 +82,7 @@ namespace Slang
     struct ParserOptions
     {
         bool enableEffectAnnotations = false;
+        bool allowGLSLInput = false;
     };
 
     // TODO: implement two pass parsing for file reference and struct type recognition
@@ -186,6 +187,7 @@ namespace Slang
         void parseSourceFile(ModuleDecl* program);
         Decl* ParseStruct();
         ClassDecl* ParseClass();
+        GLSLInterfaceBlockDecl* ParseGLSLInterfaceBlock();
         Stmt* ParseStatement(Stmt* parentStmt = nullptr);
         Stmt* parseBlockStatement();
         Stmt* parseLabelStatement();
@@ -1161,7 +1163,17 @@ namespace Slang
                         AddModifier(&modifierLink, parsedModifier);
                         continue;
                     }
-
+                    else if (parser->options.allowGLSLInput)
+                    {
+                        if (AdvanceIf(parser, "flat"))
+                        {
+                            parsedModifier = parser->astBuilder->create<HLSLNoInterpolationModifier>();
+                            parsedModifier->keywordName = nameToken.getName();
+                            parsedModifier->loc = nameToken.loc;
+                            AddModifier(&modifierLink, parsedModifier);
+                            continue;
+                        }
+                    }
                     // If there was no match for a modifier keyword, then we
                     // must be at the end of the modifier sequence
                     return modifiers;
@@ -2135,8 +2147,34 @@ namespace Slang
         memberExpr->name = expectIdentifier(parser).name;
         return memberExpr;
     }
+    
+    // Parse optional `[]` braces after a type expression, that indicate an array type
+    static Expr* parseBracketTypeSuffix(Parser* parser, Expr* inTypeExpr)
+    {
+        auto typeExpr = inTypeExpr;
+        for (;;)
+        {
+            Token token;
+            if (parser->LookAheadToken(TokenType::LBracket))
+            {
+                IndexExpr* arrType = parser->astBuilder->create<IndexExpr>();
+                arrType->loc = typeExpr->loc;
+                arrType->baseExpression = typeExpr;
+                parser->ReadToken(TokenType::LBracket);
+                if (!parser->LookAheadToken(TokenType::RBracket))
+                {
+                    arrType->indexExprs.add(parser->ParseExpression());
+                }
+                parser->ReadToken(TokenType::RBracket);
+                typeExpr = arrType;
+            }
+            else
+                break;
+        }
+        return typeExpr;
+    }
 
-    // Parse option `[]` braces after a type expression, that indicate an array type
+    // Parse option `[]` or `*` braces after a type expression, that indicate an array or pointer type
     static Expr* parsePostfixTypeSuffix(
         Parser* parser,
         Expr* inTypeExpr)
@@ -2400,7 +2438,7 @@ namespace Slang
     }
 
         /// Parse a type specifier, without dealing with modifiers.
-    static TypeSpec _parseSimpleTypeSpec(Parser* parser)
+    static TypeSpec _parseSimpleTypeSpec(Parser* parser, bool mightBeGLSLInterfaceBlock)
     {
         TypeSpec typeSpec;
 
@@ -2436,6 +2474,15 @@ namespace Slang
             typeSpec.expr = createDeclRefType(parser, decl);
             return typeSpec;
         }
+        else if( mightBeGLSLInterfaceBlock
+                && parser->LookAheadToken(TokenType::Identifier)
+                && parser->LookAheadToken(TokenType::LBrace,1) )
+        {
+            auto decl = parser->ParseGLSLInterfaceBlock();
+            typeSpec.decl = decl;
+            typeSpec.expr = createDeclRefType(parser, decl);
+            return typeSpec;
+        }
         else if(parser->LookAheadToken("enum"))
         {
             auto decl = parseEnumDecl(parser);
@@ -2493,6 +2540,19 @@ namespace Slang
         return typeSpec;
     }
 
+    static bool hasPotentialGLSLInterfaceBlockModifier(Parser* parser, Modifiers& mods)
+    {
+        if (!parser->options.allowGLSLInput)
+            return false;
+
+        for (auto mod : mods)
+        {
+            if (as<GLSLBufferModifier>(mod) || as<InModifier>(mod) || as<OutModifier>(mod))
+                return true;
+        }
+        return false;
+    }
+
         /// Parse a type specifier, following the given list of modifiers.
         ///
         /// If there are any modifiers in `ioModifiers`, this function may modify it
@@ -2501,7 +2561,7 @@ namespace Slang
         ///
     static TypeSpec _parseTypeSpec(Parser* parser, Modifiers& ioModifiers)
     {
-        TypeSpec typeSpec = _parseSimpleTypeSpec(parser);
+        TypeSpec typeSpec = _parseSimpleTypeSpec(parser, hasPotentialGLSLInterfaceBlockModifier(parser, ioModifiers));
 
         // We don't know whether `ioModifiers` has any modifiers in it,
         // or which of them might be type modifiers, so we will delegate
@@ -2526,7 +2586,7 @@ namespace Slang
     static TypeSpec _parseTypeSpec(Parser* parser)
     {
         Modifiers modifiers = ParseModifiers(parser);
-        TypeSpec typeSpec = _parseSimpleTypeSpec(parser);
+        TypeSpec typeSpec = _parseSimpleTypeSpec(parser, hasPotentialGLSLInterfaceBlockModifier(parser, modifiers));
 
         typeSpec = _applyModifiersToTypeSpec(parser, typeSpec, modifiers);
 
@@ -2549,6 +2609,7 @@ namespace Slang
             return nullptr;
         }
 
+
         // We may need to build up multiple declarations in a group,
         // but the common case will be when we have just a single
         // declaration
@@ -2560,6 +2621,11 @@ namespace Slang
         // it might declare a `struct` type.
         if(typeSpec.decl)
             declGroupBuilder.addDecl(typeSpec.decl);
+        else
+        {
+            // Allow using brackets directly after type name to declare an array typed variable.
+            typeSpec.expr = parseBracketTypeSuffix(parser, typeSpec.expr);
+        }
 
         if( AdvanceIf(parser, TokenType::Semicolon) )
         {
@@ -2960,12 +3026,9 @@ namespace Slang
         reflectionNameModifier->nameAndLoc = NameLoc(reflectionNameToken);
         addModifier(bufferVarDecl, reflectionNameModifier);
 
-        // Both the buffer variable and its type need to have names generated
-        bufferVarDecl->nameAndLoc.name = generateName(parser, "parameterGroup_" + String(reflectionNameToken.getContent()));
+        // The parameter group type need to have its name generated.
         bufferDataTypeDecl->nameAndLoc.name = generateName(parser, "ParameterGroup_" + String(reflectionNameToken.getContent()));
 
-        addModifier(bufferDataTypeDecl, parser->astBuilder->create<ImplicitParameterGroupElementTypeModifier>());
-        addModifier(bufferVarDecl, parser->astBuilder->create<ImplicitParameterGroupVariableModifier>());
 
         // TODO(tfoley): We end up constructing unchecked syntax here that
         // is expected to type check into the right form, but it might be
@@ -3003,12 +3066,28 @@ namespace Slang
         // The declarations in the body belong to the data type.
         parseDeclBody(parser, bufferDataTypeDecl);
 
-        // All HLSL buffer declarations are "transparent" in that their
-        // members are implicitly made visible in the parent scope.
-        // We achieve this by applying the transparent modifier to the variable.
-        auto transparentModifier = parser->astBuilder->create<TransparentModifier>();
-        transparentModifier->next = bufferVarDecl->modifiers.first;
-        bufferVarDecl->modifiers.first = transparentModifier;
+        if (parser->LookAheadToken(TokenType::Identifier) &&
+            parser->LookAheadToken(TokenType::Semicolon, 1))
+        {
+            // If the user specified an explicit name of the buffer var, use it.
+            bufferVarDecl->nameAndLoc = ParseDeclName(parser);
+            parser->ReadToken(TokenType::Semicolon);
+        }
+        else
+        {
+            // Otherwise, we need to generate a name for the buffer variable.
+            bufferVarDecl->nameAndLoc.name = generateName(parser, "parameterGroup_" + String(reflectionNameToken.getContent()));
+
+            // We also need to make the declaration "transparent" so that their
+            // members are implicitly made visible in the parent scope.
+            // We achieve this by applying the transparent modifier to the variable.
+            auto transparentModifier = parser->astBuilder->create<TransparentModifier>();
+            transparentModifier->next = bufferVarDecl->modifiers.first;
+            bufferVarDecl->modifiers.first = transparentModifier;
+
+            addModifier(bufferVarDecl, parser->astBuilder->create<ImplicitParameterGroupVariableModifier>());
+            addModifier(bufferDataTypeDecl, parser->astBuilder->create<ImplicitParameterGroupElementTypeModifier>());
+        }
 
         // Because we are constructing two declarations, we have a thorny
         // issue that were are only supposed to return one.
@@ -4026,6 +4105,48 @@ namespace Slang
         return nullptr;
     }
 
+    static bool parseGLSLGlobalDecl(Parser* parser, ContainerDecl* containerDecl)
+    {
+        SLANG_UNUSED(containerDecl);
+
+        if (AdvanceIf(parser, "precision"))
+        {
+            // skip global precision declarations.
+            parser->ReadToken();
+            parser->ReadToken();
+            parser->ReadToken(TokenType::Semicolon);
+            return true;
+        }
+        
+        Modifier* layoutModifier = nullptr;
+        if (parser->LookAheadToken("layout"))
+        {
+            tryParseUsingSyntaxDecl<Modifier>(parser, &layoutModifier);
+        }
+
+        DeclBase* decl = nullptr;
+        if (parser->LookAheadToken("uniform", 0) &&
+            (parser->LookAheadToken(TokenType::LBrace, 1) || 
+                parser->LookAheadToken(TokenType::Identifier, 1) &&
+                parser->LookAheadToken(TokenType::LBrace, 2)))
+        {
+            parser->ReadToken();
+            decl = as<Decl>(parseHLSLCBufferDecl(parser, containerDecl));
+            if (decl)
+                AddMember(parser->currentScope, (Decl*)decl);
+        }
+        else if (layoutModifier)
+        {
+            decl = ParseDecl(parser, containerDecl);
+        }
+
+        if (decl)
+        {
+            addModifier(decl, layoutModifier);
+            return true;
+        }
+        return false;
+    }
 
     static void parseDecls(
         Parser*             parser,
@@ -4035,6 +4156,11 @@ namespace Slang
         Token closingBraceToken;
         while (!AdvanceIfMatch(parser, matchType, &closingBraceToken))
         {
+            if (parser->options.allowGLSLInput)
+            {
+                if (parseGLSLGlobalDecl(parser, containerDecl))
+                    continue;
+            }
             ParseDecl(parser, containerDecl);
         }
         containerDecl->closingSourceLoc = closingBraceToken.loc;
@@ -4081,6 +4207,18 @@ namespace Slang
             program->loc = tokenReader.peekLoc();
         }
 
+        if (options.allowGLSLInput)
+        {
+            auto glslName = getName(this, "glsl");
+            if (program->nameAndLoc.name != glslName)
+            {
+                auto importDecl = astBuilder->create<ImportDecl>();
+                importDecl->moduleNameAndLoc.name = glslName;
+                importDecl->scope = currentScope;
+                AddMember(currentScope, importDecl);
+            }
+        }
+
         parseDecls(this, program, MatchedTokenType::File);
         PopScope();
 
@@ -4140,6 +4278,23 @@ namespace Slang
         return rs;
     }
 
+    GLSLInterfaceBlockDecl* Parser::ParseGLSLInterfaceBlock()
+    {
+        //
+        // MyBlockName { float myData[]; } myBufferName;
+        //
+
+        auto* rs = astBuilder->create<GLSLInterfaceBlockDecl>();
+        FillPosition(rs);
+
+        // As for struct, skip completion request token to prevent producing a
+        // block named completion request.
+        AdvanceIf(this, TokenType::CompletionRequest);
+        rs->nameAndLoc = expectIdentifier(this);
+        parseDeclBody(this, rs);
+        return rs;
+    }
+
     static EnumCaseDecl* parseEnumCaseDecl(Parser* parser)
     {
         EnumCaseDecl* decl = parser->astBuilder->create<EnumCaseDecl>();
@@ -4841,9 +4996,10 @@ namespace Slang
         FillPosition(stmt);
         ReadToken("for");
         ReadToken(TokenType::LParent);
-        if (peekTypeName(this))
+        auto modifiers = ParseModifiers(this);
+        if (peekTypeName(this) || !modifiers.isEmpty())
         {
-            stmt->initialStatement = parseVarDeclrStatement(Modifiers());
+            stmt->initialStatement = parseVarDeclrStatement(modifiers);
         }
         else
         {
@@ -6703,7 +6859,7 @@ namespace Slang
             // If there are any modifiers, then we know that we are actually
             // in the type case.
             //
-            auto typeSpec = _parseSimpleTypeSpec(parser);
+            auto typeSpec = _parseSimpleTypeSpec(parser, false);
             typeSpec = _applyModifiersToTypeSpec(parser, typeSpec, modifiers);
 
             auto typeExpr = typeSpec.expr;
@@ -6742,6 +6898,7 @@ namespace Slang
     {
         ParserOptions options = {};
         options.enableEffectAnnotations = translationUnit->compileRequest->getLinkage()->getEnableEffectAnnotations();
+        options.allowGLSLInput = translationUnit->compileRequest->getLinkage()->getAllowGLSLInput();
 
         Parser parser(astBuilder, tokens, sink, outerScope, options);
         parser.namePool = translationUnit->getNamePool();
@@ -6924,7 +7081,6 @@ namespace Slang
         return modifier;
     }
 
-
     static SlangResult parseSemanticVersion(Parser* parser, Token& outToken, SemanticVersion& outVersion)
     {
         parser->ReadToken(TokenType::LParent);
@@ -6981,12 +7137,12 @@ namespace Slang
         parser->sink->diagnose(token, Diagnostics::invalidCUDASMVersion);
         return nullptr;
     }
-
+    
     static NodeBase* parseLayoutModifier(Parser* parser, void* /*userData*/)
     {
         ModifierListBuilder listBuilder;
 
-        UncheckedAttribute* numThreadsAttrib = nullptr;
+        GLSLLayoutLocalSizeAttribute* numThreadsAttrib = nullptr;
 
         listBuilder.add(parser->astBuilder->create<GLSLLayoutModifierGroupBegin>());
         
@@ -7009,13 +7165,12 @@ namespace Slang
             {
                 if (!numThreadsAttrib)
                 {
-                    numThreadsAttrib = parser->astBuilder->create<UncheckedAttribute>();
+                    numThreadsAttrib = parser->astBuilder->create<GLSLLayoutLocalSizeAttribute>();
                     numThreadsAttrib->args.setCount(3);
 
                     // Just mark the loc and name from the first in the list
                     numThreadsAttrib->keywordName = getName(parser, "numthreads");
                     numThreadsAttrib->loc = nameAndLoc.loc;
-                    numThreadsAttrib->scope = parser->currentScope;
                 }
 
                 if (AdvanceIf(parser, TokenType::OpAssign))
@@ -7272,6 +7427,9 @@ namespace Slang
         _makeParseModifier("const",         ConstModifier::kReflectClassInfo),
         _makeParseModifier("instance",      InstanceModifier::kReflectClassInfo),
         _makeParseModifier("__builtin",     BuiltinModifier::kReflectClassInfo),
+        _makeParseModifier("highp",         GLSLPrecisionModifier::kReflectClassInfo),
+        _makeParseModifier("lowp",          GLSLPrecisionModifier::kReflectClassInfo),
+        _makeParseModifier("mediump",       GLSLPrecisionModifier::kReflectClassInfo),
 
         _makeParseModifier("__global",      ActualGlobalModifier::kReflectClassInfo),
 
@@ -7296,6 +7454,7 @@ namespace Slang
         _makeParseModifier("uniform",       HLSLUniformModifier::kReflectClassInfo),
         _makeParseModifier("volatile",      HLSLVolatileModifier::kReflectClassInfo),
         _makeParseModifier("export",        HLSLExportModifier::kReflectClassInfo),
+        _makeParseModifier("buffer",        GLSLBufferModifier::kReflectClassInfo),
 
         // Modifiers for geometry shader input
         _makeParseModifier("point",         HLSLPointModifier::kReflectClassInfo),
diff --git a/source/slang/slang-preprocessor.cpp b/source/slang/slang-preprocessor.cpp
index aefbf7619..02f46103b 100644
--- a/source/slang/slang-preprocessor.cpp
+++ b/source/slang/slang-preprocessor.cpp
@@ -3635,6 +3635,29 @@ static void HandlePragmaDirective(PreprocessorDirectiveContext* context)
     (subDirective->callback)(context, subDirectiveToken);
 }
 
+static void HandleExtensionDirective(PreprocessorDirectiveContext* context)
+{
+    SkipToEndOfLine(context);
+}
+
+static void HandleVersionDirective(PreprocessorDirectiveContext* context)
+{
+    [[maybe_unused]]
+    int version;
+    switch(PeekTokenType(context))
+    {
+    case TokenType::IntegerLiteral:
+        version = stringToInt(AdvanceToken(context).getContent());
+        break;
+    default:
+        GetSink(context)->diagnose(GetDirectiveLoc(context), Diagnostics::expectedIntegralVersionNumber);
+        break;
+    }
+
+    SkipToEndOfLine(context);
+    // TODO, just skip the version for now
+}
+
 // Handle an invalid directive
 static void HandleInvalidDirective(PreprocessorDirectiveContext* context)
 {
@@ -3689,6 +3712,11 @@ static const PreprocessorDirective kDirectives[] =
     { "line",       &HandleLineDirective,       0 },
     { "pragma",     &HandlePragmaDirective,     0 },
 
+    // GLSL
+    { "version",    &HandleVersionDirective,    0 },
+    { "extension",  &HandleExtensionDirective,    0 },
+
+
     { nullptr, nullptr, 0 },
 };
 
diff --git a/source/slang/slang-stdlib-textures.cpp b/source/slang/slang-stdlib-textures.cpp
index 9254bf966..98380033c 100644
--- a/source/slang/slang-stdlib-textures.cpp
+++ b/source/slang/slang-stdlib-textures.cpp
@@ -50,6 +50,7 @@ TextureTypeInfo::TextureTypeInfo(
     BaseTextureShapeInfo const& base,
     bool isArray,
     bool isMultisample,
+    bool isShadow,
     BaseTextureAccessInfo const& accessInfo,
     StringBuilder& inSB,
     String const& inPath)
@@ -57,6 +58,7 @@ TextureTypeInfo::TextureTypeInfo(
     , base(base)
     , isArray(isArray)
     , isMultisample(isMultisample)
+    , isShadow(isShadow)
     , accessInfo(accessInfo)
     , sb(inSB)
     , path(inPath)
@@ -177,7 +179,7 @@ void TextureTypeInfo::emitTypeDecl()
     unsigned flavor = baseShape;
     if (isArray)		flavor |= TextureFlavor::ArrayFlag;
     if (isMultisample)	flavor |= TextureFlavor::MultisampleFlag;
-    // if (isShadow)		flavor |= TextureFlavor::ShadowFlag;
+    if (isShadow)		flavor |= TextureFlavor::ShadowFlag;
 
     flavor |= (access << 8);
 
@@ -204,7 +206,7 @@ void TextureTypeInfo::emitTypeDecl()
     sb << baseShapeName;
     if (isMultisample) sb << "MS";
     if (isArray) sb << "Array";
-    // if (isShadow) sb << "Shadow";
+    if (isShadow) sb << "Shadow";
     sb << "\n";
 
     // The struct body
@@ -988,7 +990,7 @@ void TextureTypeInfo::writeSampleFunctions()
 {
     TextureFlavor::Shape baseShape = base.baseShape;
     char const* samplerStateParam = prefixInfo.combined ? "" : "SamplerState s, ";
-
+    char const* comparisonSamplerStateParam = prefixInfo.combined ? "" : "SamplerComparisonState s, ";
     // `Sample()`
 
     writeFunc(
@@ -1081,7 +1083,7 @@ void TextureTypeInfo::writeSampleFunctions()
             "float",
             "SampleCmp",
             cat(
-                "SamplerComparisonState s, ",
+                comparisonSamplerStateParam,
                 "float", base.coordCount + isArray, " location, ",
                 "float compareValue"
             ),
@@ -1093,7 +1095,7 @@ void TextureTypeInfo::writeSampleFunctions()
             "float",
             "SampleCmpLevelZero",
             cat(
-                "SamplerComparisonState s, ",
+                comparisonSamplerStateParam,
                 "float", base.coordCount + isArray, " location, ",
                 "float compareValue"
             ),
@@ -1113,7 +1115,7 @@ void TextureTypeInfo::writeSampleFunctions()
             "float",
             "SampleCmp",
             cat(
-                "SamplerComparisonState s, ",
+                comparisonSamplerStateParam,
                 "float", base.coordCount + isArray, " location, ",
                 "float compareValue, "
                 "constexpr int", base.coordCount, " offset"
@@ -1126,7 +1128,7 @@ void TextureTypeInfo::writeSampleFunctions()
             "float",
             "SampleCmpLevelZero",
             cat(
-                "SamplerComparisonState s, ",
+                comparisonSamplerStateParam,
                 "float", base.coordCount + isArray, " location, ",
                 "float compareValue, "
                 "constexpr int", base.coordCount, " offset"
diff --git a/source/slang/slang-stdlib-textures.h b/source/slang/slang-stdlib-textures.h
index 19008a3f0..dc2f64a41 100644
--- a/source/slang/slang-stdlib-textures.h
+++ b/source/slang/slang-stdlib-textures.h
@@ -44,6 +44,7 @@ struct TextureTypeInfo
         BaseTextureShapeInfo const& base,
         bool isArray,
         bool isMultisample,
+        bool isShadow,
         BaseTextureAccessInfo const& accessInfo,
         StringBuilder& inSB,
         String const& inPath);
@@ -52,6 +53,7 @@ struct TextureTypeInfo
     BaseTextureShapeInfo const& base;
     bool isArray;
     bool isMultisample;
+    bool isShadow;
     BaseTextureAccessInfo const& accessInfo;
     StringBuilder& sb;
     String path;
diff --git a/source/slang/slang-stdlib.cpp b/source/slang/slang-stdlib.cpp
index 5fec05c80..5a977694a 100644
--- a/source/slang/slang-stdlib.cpp
+++ b/source/slang/slang-stdlib.cpp
@@ -335,4 +335,16 @@ namespace Slang
 #endif
         return autodiffLibraryCode;
     }
+
+    ComPtr<ISlangBlob> Session::getGLSLLibraryCode()
+    {
+        if (!glslLibraryCode)
+        {
+            const String path = getStdlibPath();
+            StringBuilder sb;
+#include "glsl.meta.slang.h"
+            glslLibraryCode = StringBlob::moveCreate(sb);
+        }
+        return glslLibraryCode;
+    }
 }
diff --git a/source/slang/slang-type-system-shared.h b/source/slang/slang-type-system-shared.h
index 2e824e0a0..4fa48d23e 100644
--- a/source/slang/slang-type-system-shared.h
+++ b/source/slang/slang-type-system-shared.h
@@ -48,9 +48,7 @@ FOREACH_BASE_TYPE(DEFINE_BASE_TYPE)
             MultisampleFlag = SLANG_TEXTURE_MULTISAMPLE_FLAG,
 
             // Whether or not this is a shadow texture
-            //
-            // TODO(tfoley): is this even meaningful/used?
-            // ShadowFlag		= 0x80,
+            ShadowFlag		= SLANG_TEXTURE_SHADOW_FLAG,
 
             // For feedback texture
             FeedbackFlag = SLANG_TEXTURE_FEEDBACK_FLAG,
@@ -84,7 +82,7 @@ FOREACH_BASE_TYPE(DEFINE_BASE_TYPE)
         bool isArray() const { return (flavor & ArrayFlag) != 0; }
         bool isMultisample() const { return (flavor & MultisampleFlag) != 0; }
         bool isFeedback() const { return (flavor & FeedbackFlag) != 0; }
-        //            bool isShadow() const { return (flavor & ShadowFlag) != 0; }
+        bool isShadow() const { return (flavor & ShadowFlag) != 0; }
 
         SLANG_FORCE_INLINE bool operator==(const ThisType& rhs) const { return flavor == rhs.flavor; }
         SLANG_FORCE_INLINE bool operator!=(const ThisType& rhs) const { return !(*this == rhs); }
diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index af853102a..0331a5f8e 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -2534,22 +2534,26 @@ SlangResult FrontEndCompileRequest::executeActionsInner()
 {
     SLANG_AST_BUILDER_RAII(getLinkage()->getASTBuilder());
 
-    // We currently allow GlSL files on the command line so that we can
-    // drive our "pass-through" mode, but we really want to issue an error
-    // message if the user is seriously asking us to compile them.
     for (TranslationUnitRequest* translationUnit : translationUnits)
     {
         // Make sure SourceFile representation is available for all translationUnits
         SLANG_RETURN_ON_FAIL(translationUnit->requireSourceFiles());
 
-        switch(translationUnit->sourceLanguage)
+        if(!getLinkage()->getAllowGLSLInput())
         {
-        default:
-            break;
+            // We currently allow GlSL files on the command line so that we can
+            // drive our "pass-through" mode, but we really want to issue an error
+            // message if the user is seriously asking us to compile them and
+            // doesn't explicitly opt into the glsl frontend
+            switch(translationUnit->sourceLanguage)
+            {
+            default:
+                break;
 
-        case SourceLanguage::GLSL:
-            getSink()->diagnose(SourceLoc(), Diagnostics::glslIsNotSupported);
-            return SLANG_FAIL;
+            case SourceLanguage::GLSL:
+                getSink()->diagnose(SourceLoc(), Diagnostics::glslIsNotSupported);
+                return SLANG_FAIL;
+            }
         }
     }
 
@@ -3230,12 +3234,23 @@ RefPtr<Module> Linkage::findOrImportModule(
     PathInfo pathIncludedFromInfo = getSourceManager()->getPathInfo(loc, SourceLocType::Actual);
     PathInfo filePathInfo;
 
+    ComPtr<ISlangBlob> fileContents;
+
     // We have to load via the found path - as that is how file was originally loaded
     if (SLANG_FAILED(includeSystem.findFile(fileName, pathIncludedFromInfo.foundPath, filePathInfo)))
     {
-        sink->diagnose(loc, Diagnostics::cannotFindFile, fileName);
-        mapNameToLoadedModules[name] = nullptr;
-        return nullptr;
+        if (name && name->text == "glsl")
+        {
+            // This is a builtin glsl module, just load it from embedded definition.
+            fileContents = getSessionImpl()->getGLSLLibraryCode();
+            filePathInfo = PathInfo::makeFromString("glsl");
+        }
+        else
+        {
+            sink->diagnose(loc, Diagnostics::cannotFindFile, fileName);
+            mapNameToLoadedModules[name] = nullptr;
+            return nullptr;
+        }
     }
 
     // Maybe this was loaded previously at a different relative name?
@@ -3243,8 +3258,7 @@ RefPtr<Module> Linkage::findOrImportModule(
         return loadedModule;
 
     // Try to load it
-    ComPtr<ISlangBlob> fileContents;
-    if(SLANG_FAILED(includeSystem.loadFile(filePathInfo, fileContents)))
+    if( !fileContents && SLANG_FAILED(includeSystem.loadFile(filePathInfo, fileContents)))
     {
         sink->diagnose(loc, Diagnostics::cannotOpenFile, fileName);
         mapNameToLoadedModules[name] = nullptr;
@@ -5267,6 +5281,11 @@ SlangResult EndToEndCompileRequest::setTypeNameForEntryPointExistentialTypeParam
     return SLANG_OK;
 }
 
+void EndToEndCompileRequest::setAllowGLSLInput(bool value)
+{
+    getLinkage()->setAllowGLSLInput(value);
+}
+
 SlangResult EndToEndCompileRequest::EndToEndCompileRequest::compile()
 {
     SlangResult res = SLANG_FAIL;