shader: Implement miss attribute layer

src/shader_recompiler/backend/glasm/emit_glasm.cpp

@@ -320,6 +320,7 @@ void SetupOptions(const IR::Program& program, const Profile& profile,
     }
     if (stage == Stage::Fragment) {
         header += "OPTION ARB_draw_buffers;";
+        header += "OPTION ARB_fragment_layer_viewport;";
     }
 }
 

src/shader_recompiler/backend/glasm/emit_glasm_context_get_set.cpp

@@ -104,6 +104,9 @@ void EmitGetAttribute(EmitContext& ctx, IR::Inst& inst, IR::Attribute attr, Scal
     case IR::Attribute::PrimitiveId:
         ctx.Add("MOV.F {}.x,primitive.id;", inst);
         break;
+    case IR::Attribute::Layer:
+        ctx.Add("MOV.F {}.x,fragment.layer;", inst);
+        break;
     case IR::Attribute::PositionX:
     case IR::Attribute::PositionY:
     case IR::Attribute::PositionZ:

src/shader_recompiler/backend/glsl/emit_glsl_context_get_set.cpp

@@ -205,6 +205,9 @@ void EmitGetAttribute(EmitContext& ctx, IR::Inst& inst, IR::Attribute attr,
     case IR::Attribute::PrimitiveId:
         ctx.AddF32("{}=itof(gl_PrimitiveID);", inst);
         break;
+    case IR::Attribute::Layer:
+        ctx.AddF32("{}=itof(gl_Layer);", inst);
+        break;
     case IR::Attribute::PositionX:
     case IR::Attribute::PositionY:
     case IR::Attribute::PositionZ:

src/shader_recompiler/backend/spirv/emit_spirv_context_get_set.cpp

@@ -315,6 +315,8 @@ Id EmitGetAttribute(EmitContext& ctx, IR::Attribute attr, Id vertex) {
     switch (attr) {
     case IR::Attribute::PrimitiveId:
         return ctx.OpBitcast(ctx.F32[1], ctx.OpLoad(ctx.U32[1], ctx.primitive_id));
+    case IR::Attribute::Layer:
+        return ctx.OpBitcast(ctx.F32[1], ctx.OpLoad(ctx.U32[1], ctx.layer));
     case IR::Attribute::PositionX:
     case IR::Attribute::PositionY:
     case IR::Attribute::PositionZ:

src/shader_recompiler/backend/spirv/spirv_emit_context.cpp

@@ -1355,6 +1355,10 @@ void EmitContext::DefineInputs(const IR::Program& program) {
     if (loads[IR::Attribute::PrimitiveId]) {
         primitive_id = DefineInput(*this, U32[1], false, spv::BuiltIn::PrimitiveId);
     }
+    if (loads[IR::Attribute::Layer]) {
+        AddCapability(spv::Capability::Geometry);
+        layer = DefineInput(*this, U32[1], false, spv::BuiltIn::Layer);
+    }
     if (loads.AnyComponent(IR::Attribute::PositionX)) {
         const bool is_fragment{stage != Stage::Fragment};
         const spv::BuiltIn built_in{is_fragment ? spv::BuiltIn::Position : spv::BuiltIn::FragCoord};