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, 35 insertions, 3 deletions

diff --git a/source/slang/slang-emit-hlsl.cpp b/source/slang/slang-emit-hlsl.cpp
index 187115232..8891f06a6 100644
--- a/source/slang/slang-emit-hlsl.cpp
+++ b/source/slang/slang-emit-hlsl.cpp
@@ -313,9 +313,7 @@ void HLSLSourceEmitter::emitEntryPointAttributesImpl(IRFunc* irFunc, IREntryPoin
         }
     }
 
-    switch (stage)
-    {
-        case Stage::Compute:
+    auto emitNumThreadsAttribute = [&]()
         {
             Int sizeAlongAxis[kThreadGroupAxisCount];
             getComputeThreadGroupSize(irFunc, sizeAlongAxis);
@@ -327,6 +325,13 @@ void HLSLSourceEmitter::emitEntryPointAttributesImpl(IRFunc* irFunc, IREntryPoin
                 m_writer->emit(sizeAlongAxis[ii]);
             }
             m_writer->emit(")]\n");
+        };
+
+    switch (stage)
+    {
+        case Stage::Compute:
+        {
+            emitNumThreadsAttribute();
         }
         break;
         case Stage::Geometry:
@@ -406,6 +411,18 @@ void HLSLSourceEmitter::emitEntryPointAttributesImpl(IRFunc* irFunc, IREntryPoin
             }
             break;
         }
+        case Stage::Mesh:
+        {
+            emitNumThreadsAttribute();
+            if (auto decor = irFunc->findDecoration<IROutputTopologyDecoration>())
+            {
+                // TODO: Ellie validate here/elsewhere, what's allowed here is
+                // different from the tesselator
+                // The naming here is plural, so add an 's'
+                _emitHLSLDecorationSingleString("outputtopology", irFunc, decor->getTopology());
+            }
+            break;
+        }
         // TODO: There are other stages that will need this kind of handling.
         default:
             break;
@@ -1052,6 +1069,7 @@ void HLSLSourceEmitter::_emitPrefixTypeAttr(IRAttr* attr)
 void HLSLSourceEmitter::emitSimpleFuncParamImpl(IRParam* param)
 {
     emitRateQualifiers(param);
+    emitMeshOutputModifiers(param);
 
     if (auto decor = param->findDecoration<IRGeometryInputPrimitiveTypeDecoration>())
     {
@@ -1104,6 +1122,20 @@ void HLSLSourceEmitter::emitInterpolationModifiersImpl(IRInst* varInst, IRType*
     }
 }
 
+void HLSLSourceEmitter::emitMeshOutputModifiersImpl(IRInst* varInst)
+{
+    if(auto modifier = varInst->findDecoration<IRMeshOutputDecoration>())
+    {
+        const char* s =
+              as<IRVerticesDecoration>(modifier)   ? "vertices "
+            : as<IRIndicesDecoration>(modifier)    ? "indices "
+            : as<IRPrimitivesDecoration>(modifier) ? "primitives "
+            : nullptr;
+        SLANG_EXPECT(s, "Unhandled type of mesh output decoration");
+        m_writer->emit(s);
+    }
+}
+
 void HLSLSourceEmitter::emitVarDecorationsImpl(IRInst* varDecl)
 {
     if (varDecl->findDecoration<IRGloballyCoherentDecoration>())