shader_decompiler: Remove FragCoord.w hack and change IPA implementation

Credits go to gdkchan and Ryujinx. The pull request used for this can
be found here: https://github.com/Ryujinx/Ryujinx/pull/1082

yuzu was already using the header for interpolation, but it was missing
the FragCoord.w multiplication described in the linked pull request.
This commit finally removes the FragCoord.w == 1.0f hack from the shader
decompiler.

While we are at it, this commit renames some enumerations to match
Nvidia's documentation (linked below) and fixes component declaration
order in the shader program header (z and w were swapped).

https://github.com/NVIDIA/open-gpu-doc/blob/master/Shader-Program-Header/Shader-Program-Header.html

1 files changed, 16 insertions, 18 deletions

diff --git a/src/video_core/renderer_opengl/gl_shader_decompiler.cpp b/src/video_core/renderer_opengl/gl_shader_decompiler.cpp
index c7d24cf14..160ae4340 100644
--- a/src/video_core/renderer_opengl/gl_shader_decompiler.cpp
+++ b/src/video_core/renderer_opengl/gl_shader_decompiler.cpp
@@ -31,11 +31,11 @@ namespace {
 
 using Tegra::Engines::ShaderType;
 using Tegra::Shader::Attribute;
-using Tegra::Shader::AttributeUse;
 using Tegra::Shader::Header;
 using Tegra::Shader::IpaInterpMode;
 using Tegra::Shader::IpaMode;
 using Tegra::Shader::IpaSampleMode;
+using Tegra::Shader::PixelImap;
 using Tegra::Shader::Register;
 using VideoCommon::Shader::BuildTransformFeedback;
 using VideoCommon::Shader::Registry;
@@ -702,20 +702,19 @@ private:
         code.AddNewLine();
     }
 
-    std::string GetInputFlags(AttributeUse attribute) {
+    const char* GetInputFlags(PixelImap attribute) {
         switch (attribute) {
-        case AttributeUse::Perspective:
-            // Default, Smooth
-            return {};
-        case AttributeUse::Constant:
-            return "flat ";
-        case AttributeUse::ScreenLinear:
-            return "noperspective ";
-        default:
-        case AttributeUse::Unused:
-            UNIMPLEMENTED_MSG("Unknown attribute usage index={}", static_cast<u32>(attribute));
-            return {};
+        case PixelImap::Perspective:
+            return "smooth";
+        case PixelImap::Constant:
+            return "flat";
+        case PixelImap::ScreenLinear:
+            return "noperspective";
+        case PixelImap::Unused:
+            break;
         }
+        UNIMPLEMENTED_MSG("Unknown attribute usage index={}", static_cast<int>(attribute));
+        return {};
     }
 
     void DeclareInputAttributes() {
@@ -749,8 +748,8 @@ private:
 
         std::string suffix;
         if (stage == ShaderType::Fragment) {
-            const auto input_mode{header.ps.GetAttributeUse(location)};
-            if (skip_unused && input_mode == AttributeUse::Unused) {
+            const auto input_mode{header.ps.GetPixelImap(location)};
+            if (input_mode == PixelImap::Unused) {
                 return;
             }
             suffix = GetInputFlags(input_mode);
@@ -927,7 +926,7 @@ private:
                 const u32 address{generic_base + index * generic_stride + element * element_stride};
 
                 const bool declared = stage != ShaderType::Fragment ||
-                                      header.ps.GetAttributeUse(index) != AttributeUse::Unused;
+                                      header.ps.GetPixelImap(index) != PixelImap::Unused;
                 const std::string value =
                     declared ? ReadAttribute(attribute, element).AsFloat() : "0.0f";
                 code.AddLine("case 0x{:X}U: return {};", address, value);
@@ -1142,8 +1141,7 @@ private:
                                     GetSwizzle(element)),
                         Type::Float};
             case ShaderType::Fragment:
-                return {element == 3 ? "1.0f" : ("gl_FragCoord"s + GetSwizzle(element)),
-                        Type::Float};
+                return {"gl_FragCoord"s + GetSwizzle(element), Type::Float};
             default:
                 UNREACHABLE();
             }