shader: Properly manage attributes not written from previous stages

src/shader_recompiler/backend/glsl/emit_context.cpp

@@ -327,11 +327,12 @@ EmitContext::EmitContext(IR::Program& program, Bindings& bindings, const Profile
 
     for (size_t index = 0; index < info.input_generics.size(); ++index) {
         const auto& generic{info.input_generics[index]};
-        if (generic.used) {
-            header += fmt::format("layout(location={}){}in vec4 in_attr{}{};", index,
-                                  InterpDecorator(generic.interpolation), index,
-                                  InputArrayDecorator(stage));
+        if (!generic.used || !runtime_info.previous_stage_stores_generic[index]) {
+            continue;
         }
+        header +=
+            fmt::format("layout(location={}){}in vec4 in_attr{}{};", index,
+                        InterpDecorator(generic.interpolation), index, InputArrayDecorator(stage));
     }
     for (size_t index = 0; index < info.uses_patches.size(); ++index) {
         if (!info.uses_patches[index]) {
@@ -349,10 +350,10 @@ EmitContext::EmitContext(IR::Program& program, Bindings& bindings, const Profile
         }
     }
     for (size_t index = 0; index < info.stores_generics.size(); ++index) {
-        // TODO: Properly resolve attribute issues
-        if (info.stores_generics[index] || StageInitializesVaryings()) {
-            DefineGenericOutput(index, program.invocations);
+        if (!info.stores_generics[index]) {
+            continue;
         }
+        DefineGenericOutput(index, program.invocations);
     }
     DefineConstantBuffers(bindings);
     DefineStorageBuffers(bindings);
@@ -362,17 +363,6 @@ EmitContext::EmitContext(IR::Program& program, Bindings& bindings, const Profile
     DefineConstants();
 }
 
-bool EmitContext::StageInitializesVaryings() const noexcept {
-    switch (stage) {
-    case Stage::VertexA:
-    case Stage::VertexB:
-    case Stage::Geometry:
-        return true;
-    default:
-        return false;
-    }
-}
-
 void EmitContext::SetupExtensions() {
     if (info.uses_shadow_lod && profile.support_gl_texture_shadow_lod) {
         header += "#extension GL_EXT_texture_shadow_lod : enable\n";

src/shader_recompiler/backend/glsl/emit_context.h

@@ -136,8 +136,6 @@ public:
         code += '\n';
     }
 
-    [[nodiscard]] bool StageInitializesVaryings() const noexcept;
-
     std::string header;
     std::string code;
     VarAlloc var_alloc;

src/shader_recompiler/backend/glsl/emit_glsl_context_get_set.cpp

@@ -8,6 +8,7 @@
 #include "shader_recompiler/backend/glsl/emit_glsl_instructions.h"
 #include "shader_recompiler/frontend/ir/value.h"
 #include "shader_recompiler/profile.h"
+#include "shader_recompiler/runtime_info.h"
 
 namespace Shader::Backend::GLSL {
 namespace {
@@ -179,6 +180,10 @@ void EmitGetAttribute(EmitContext& ctx, IR::Inst& inst, IR::Attribute attr,
     const char swizzle{"xyzw"[element]};
     if (IR::IsGeneric(attr)) {
         const u32 index{IR::GenericAttributeIndex(attr)};
+        if (!ctx.runtime_info.previous_stage_stores_generic[index]) {
+            ctx.AddF32("{}=0.f;", inst, attr);
+            return;
+        }
         ctx.AddF32("{}=in_attr{}{}.{};", inst, index, InputVertexIndex(ctx, vertex), swizzle);
         return;
     }

src/shader_recompiler/backend/glsl/emit_glsl_special.cpp

@@ -12,11 +12,12 @@
 
 namespace Shader::Backend::GLSL {
 namespace {
-void InitializeVaryings(EmitContext& ctx) {
-    ctx.Add("gl_Position=vec4(0,0,0,1);");
-    // TODO: Properly resolve attribute issues
-    for (size_t index = 0; index < ctx.info.stores_generics.size() / 2; ++index) {
-        if (!ctx.info.stores_generics[index]) {
+void InitializeOutputVaryings(EmitContext& ctx) {
+    if (ctx.stage == Stage::VertexB || ctx.stage == Stage::Geometry) {
+        ctx.Add("gl_Position=vec4(0,0,0,1);");
+    }
+    for (size_t index = 0; index < 16; ++index) {
+        if (ctx.info.stores_generics[index]) {
             ctx.Add("out_attr{}=vec4(0,0,0,1);", index);
         }
     }
@@ -56,9 +57,8 @@ void EmitPhiMove(EmitContext& ctx, const IR::Value& phi_value, const IR::Value&
 }
 
 void EmitPrologue(EmitContext& ctx) {
-    if (ctx.StageInitializesVaryings()) {
-        InitializeVaryings(ctx);
-    }
+    InitializeOutputVaryings(ctx);
+
     if (ctx.stage == Stage::Fragment && ctx.profile.need_declared_frag_colors) {
         for (size_t index = 0; index < ctx.info.stores_frag_color.size(); ++index) {
             if (ctx.info.stores_frag_color[index]) {
@@ -73,7 +73,7 @@ void EmitEpilogue(EmitContext&) {}
 
 void EmitEmitVertex(EmitContext& ctx, const IR::Value& stream) {
     ctx.Add("EmitStreamVertex(int({}));", ctx.var_alloc.Consume(stream));
-    InitializeVaryings(ctx);
+    InitializeOutputVaryings(ctx);
 }
 
 void EmitEndPrimitive(EmitContext& ctx, const IR::Value& stream) {

src/shader_recompiler/backend/spirv/emit_context.cpp

@@ -1209,6 +1209,9 @@ void EmitContext::DefineInputs(const Info& info) {
         tess_coord = DefineInput(*this, F32[3], false, spv::BuiltIn::TessCoord);
     }
     for (size_t index = 0; index < info.input_generics.size(); ++index) {
+        if (!runtime_info.previous_stage_stores_generic[index]) {
+            continue;
+        }
         const InputVarying generic{info.input_generics[index]};
         if (!generic.used) {
             continue;

src/shader_recompiler/backend/spirv/emit_spirv_context_get_set.cpp

@@ -286,7 +286,7 @@ Id EmitGetAttribute(EmitContext& ctx, IR::Attribute attr, Id vertex) {
     if (IR::IsGeneric(attr)) {
         const u32 index{IR::GenericAttributeIndex(attr)};
         const std::optional<AttrInfo> type{AttrTypes(ctx, index)};
-        if (!type) {
+        if (!type || !ctx.runtime_info.previous_stage_stores_generic[index]) {
             // Attribute is disabled
             return ctx.Const(0.0f);
         }