vk_shader_decompiler: Disable default values on unwritten render targets

Some games like The Legend of Zelda: Breath of the Wild assign
render targets without writing them from the fragment shader. This
generates Vulkan validation errors, so silence these I previously
introduced a commit to set "vec4(0, 0, 0, 1)" for these attachments. The
problem is that this is not what games expect. This commit reverts that
change.

src/video_core/renderer_vulkan/vk_pipeline_cache.cpp

@@ -325,9 +325,6 @@ VKPipelineCache::DecompileShaders(const GraphicsPipelineCacheKey& key) {
     specialization.tessellation.primitive = fixed_state.tessellation.primitive;
     specialization.tessellation.spacing = fixed_state.tessellation.spacing;
     specialization.tessellation.clockwise = fixed_state.tessellation.clockwise;
-    for (const auto& rt : key.renderpass_params.color_attachments) {
-        specialization.enabled_rendertargets.set(rt.index);
-    }
 
     SPIRVProgram program;
     std::vector<vk::DescriptorSetLayoutBinding> bindings;

src/video_core/renderer_vulkan/vk_shader_decompiler.cpp

@@ -542,11 +542,10 @@ private:
             return;
         }
 
-        for (u32 rt = 0; rt < static_cast<u32>(frag_colors.size()); ++rt) {
-            if (!specialization.enabled_rendertargets[rt]) {
+        for (u32 rt = 0; rt < static_cast<u32>(std::size(frag_colors)); ++rt) {
+            if (!IsRenderTargetEnabled(rt)) {
                 continue;
             }
-
             const Id id = AddGlobalVariable(OpVariable(t_out_float4, spv::StorageClass::Output));
             Name(id, fmt::format("frag_color{}", rt));
             Decorate(id, spv::Decoration::Location, rt);
@@ -852,6 +851,15 @@ private:
         return binding;
     }
 
+    bool IsRenderTargetEnabled(u32 rt) const {
+        for (u32 component = 0; component < 4; ++component) {
+            if (header.ps.IsColorComponentOutputEnabled(rt, component)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     bool IsInputAttributeArray() const {
         return stage == ShaderType::TesselationControl || stage == ShaderType::TesselationEval ||
                stage == ShaderType::Geometry;
@@ -1889,19 +1897,14 @@ private:
             // rendertargets/components are skipped in the register assignment.
             u32 current_reg = 0;
             for (u32 rt = 0; rt < Maxwell::NumRenderTargets; ++rt) {
-                if (!specialization.enabled_rendertargets[rt]) {
-                    // Skip rendertargets that are not enabled
-                    continue;
-                }
                 // TODO(Subv): Figure out how dual-source blending is configured in the Switch.
                 for (u32 component = 0; component < 4; ++component) {
-                    const Id pointer = AccessElement(t_out_float, frag_colors.at(rt), component);
-                    if (header.ps.IsColorComponentOutputEnabled(rt, component)) {
+                    if (!header.ps.IsColorComponentOutputEnabled(rt, component)) {
+                        continue;
+                    }
+                    const Id pointer = AccessElement(t_out_float, frag_colors[rt], component);
                     OpStore(pointer, SafeGetRegister(current_reg));
                     ++current_reg;
-                    } else {
-                        OpStore(pointer, component == 3 ? v_float_one : v_float_zero);
-                    }
                 }
             }
             if (header.ps.omap.depth) {

src/video_core/renderer_vulkan/vk_shader_decompiler.h

@@ -102,9 +102,6 @@ struct Specialization final {
         Maxwell::TessellationSpacing spacing{};
         bool clockwise{};
     } tessellation;
-
-    // Fragment specific
-    std::bitset<8> enabled_rendertargets;
 };
 // Old gcc versions don't consider this trivially copyable.
 // static_assert(std::is_trivially_copyable_v<Specialization>);