Mesh shader support (#2464)

* Add gdb generated files to .gitignore

* Switch to c++17

TODO: Ellie update coding style doc

* WIP mesh shaders

* Add MeshOutputType and mesh output decorations

* Lift array type layout creation out of _createTypeLayout

in preparation for sharing it elsewhere

* Initial pass at GLSL legalization for mesh shaders

* Create output types for builtin mesh outputs

This should be rendered as an out paramter block

* Handle writes to member fields in mesh shader output

* Per primitive output from mesh shaders

* Add mesh shader tests

* Redeclare mesh output builtins

* Remove unused instruction

* Emit explicit mesh output max max size

* Add unimplemented warning for array members in mesh output

* Implement mesh output splitting for GLSL in terms of getSubscriptVal

* Allow HLSL syntax for mesh output modifiers

* Improve error messages for mesh output

* Add test for HLSL style mesh output syntax

* Emit explicit mesh output indices max size

* HLSL generation support for mesh shaders

* Better errors for mesh shader misuse

* Neaten comments

* Regenerate vs2019 project files

* Fix build on vs2019

* Retreat on c++17

Will make the change in a separate PR

* slang-glslang binary dep 11.10.0 -> 11.12.0-32

* Fixes for msvc compiler

* Update msvc project

1 files changed, 16 insertions, 0 deletions

diff --git a/source/slang/slang-syntax.cpp b/source/slang/slang-syntax.cpp
index f3b590acf..80f57905f 100644
--- a/source/slang/slang-syntax.cpp
+++ b/source/slang/slang-syntax.cpp
@@ -1065,6 +1065,22 @@ Index getFilterCountImpl(const ReflectClassInfo& clsInfo, MemberFilterStyle filt
         return as<IntVal>(findInnerMostGenericSubstitution(declRef.substitutions)->getArgs()[1]);
     }
 
+    // MeshOutputType
+    // There's a subtle distinction between this and HLSLPatchType, the size
+    // here is the max possible size of the array, it's free to change at
+    // runtime. There's probably no circumstance where you'd want to be generic
+    // between the two, so we don't deduplicate this code.
+
+    Type* MeshOutputType::getElementType()
+    {
+        return as<Type>(findInnerMostGenericSubstitution(declRef.substitutions)->getArgs()[0]);
+    }
+
+    IntVal* MeshOutputType::getMaxElementCount()
+    {
+        return as<IntVal>(findInnerMostGenericSubstitution(declRef.substitutions)->getArgs()[1]);
+    }
+
     // Constructors for types
 
     ArrayExpressionType* getArrayType(