4 files changed, 74 insertions, 68 deletions

diff --git a/src/video_core/engines/shader_header.h b/src/video_core/engines/shader_header.h
index bc80661d8..72e2a33d5 100644
--- a/src/video_core/engines/shader_header.h
+++ b/src/video_core/engines/shader_header.h
@@ -4,6 +4,9 @@
 
 #pragma once
 
+#include <array>
+#include <optional>
+
 #include "common/bit_field.h"
 #include "common/common_funcs.h"
 #include "common/common_types.h"
@@ -16,7 +19,7 @@ enum class OutputTopology : u32 {
     TriangleStrip = 7,
 };
 
-enum class AttributeUse : u8 {
+enum class PixelImap : u8 {
     Unused = 0,
     Constant = 1,
     Perspective = 2,
@@ -24,7 +27,7 @@ enum class AttributeUse : u8 {
 };
 
 // Documentation in:
-// http://download.nvidia.com/open-gpu-doc/Shader-Program-Header/1/Shader-Program-Header.html#ImapTexture
+// http://download.nvidia.com/open-gpu-doc/Shader-Program-Header/1/Shader-Program-Header.html
 struct Header {
     union {
         BitField<0, 5, u32> sph_type;
@@ -59,8 +62,8 @@ struct Header {
     union {
         BitField<0, 12, u32> max_output_vertices;
         BitField<12, 8, u32> store_req_start; // NOTE: not used by geometry shaders.
-        BitField<24, 4, u32> reserved;
-        BitField<12, 8, u32> store_req_end; // NOTE: not used by geometry shaders.
+        BitField<20, 4, u32> reserved;
+        BitField<24, 8, u32> store_req_end; // NOTE: not used by geometry shaders.
     } common4{};
 
     union {
@@ -93,17 +96,20 @@ struct Header {
         struct {
             INSERT_UNION_PADDING_BYTES(3); // ImapSystemValuesA
             INSERT_UNION_PADDING_BYTES(1); // ImapSystemValuesB
+
             union {
-                BitField<0, 2, AttributeUse> x;
-                BitField<2, 2, AttributeUse> y;
-                BitField<4, 2, AttributeUse> w;
-                BitField<6, 2, AttributeUse> z;
+                BitField<0, 2, PixelImap> x;
+                BitField<2, 2, PixelImap> y;
+                BitField<4, 2, PixelImap> z;
+                BitField<6, 2, PixelImap> w;
                 u8 raw;
             } imap_generic_vector[32];
+
             INSERT_UNION_PADDING_BYTES(2);  // ImapColor
             INSERT_UNION_PADDING_BYTES(2);  // ImapSystemValuesC
             INSERT_UNION_PADDING_BYTES(10); // ImapFixedFncTexture[10]
             INSERT_UNION_PADDING_BYTES(2);  // ImapReserved
+
             struct {
                 u32 target;
                 union {
@@ -112,31 +118,30 @@ struct Header {
                     BitField<2, 30, u32> reserved;
                 };
             } omap;
+
             bool IsColorComponentOutputEnabled(u32 render_target, u32 component) const {
                 const u32 bit = render_target * 4 + component;
                 return omap.target & (1 << bit);
             }
-            AttributeUse GetAttributeIndexUse(u32 attribute, u32 index) const {
-                return static_cast<AttributeUse>(
-                    (imap_generic_vector[attribute].raw >> (index * 2)) & 0x03);
-            }
-            AttributeUse GetAttributeUse(u32 attribute) const {
-                AttributeUse result = AttributeUse::Unused;
-                for (u32 i = 0; i < 4; i++) {
-                    const auto index = GetAttributeIndexUse(attribute, i);
-                    if (index == AttributeUse::Unused) {
-                        continue;
-                    }
-                    if (result == AttributeUse::Unused || result == index) {
-                        result = index;
+
+            PixelImap GetPixelImap(u32 attribute) const {
+                const auto get_index = [this, attribute](u32 index) {
+                    return static_cast<PixelImap>(
+                        (imap_generic_vector[attribute].raw >> (index * 2)) & 3);
+                };
+
+                std::optional<PixelImap> result;
+                for (u32 component = 0; component < 4; ++component) {
+                    const PixelImap index = get_index(component);
+                    if (index == PixelImap::Unused) {
                         continue;
                     }
-                    LOG_CRITICAL(HW_GPU, "Generic Attribute Conflict in Interpolation Mode");
-                    if (index == AttributeUse::Perspective) {
-                        result = index;
+                    if (result && result != index) {
+                        LOG_CRITICAL(HW_GPU, "Generic attribute conflict in interpolation mode");
                     }
+                    result = index;
                 }
-                return result;
+                return result.value_or(PixelImap::Unused);
             }
         } ps;
 
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();
             }
diff --git a/src/video_core/renderer_vulkan/vk_shader_decompiler.cpp b/src/video_core/renderer_vulkan/vk_shader_decompiler.cpp
index d67f08cf9..b9f9e2714 100644
--- a/src/video_core/renderer_vulkan/vk_shader_decompiler.cpp
+++ b/src/video_core/renderer_vulkan/vk_shader_decompiler.cpp
@@ -35,7 +35,7 @@ namespace {
 using Sirit::Id;
 using Tegra::Engines::ShaderType;
 using Tegra::Shader::Attribute;
-using Tegra::Shader::AttributeUse;
+using Tegra::Shader::PixelImap;
 using Tegra::Shader::Register;
 using namespace VideoCommon::Shader;
 
@@ -752,16 +752,16 @@ private:
             if (stage != ShaderType::Fragment) {
                 continue;
             }
-            switch (header.ps.GetAttributeUse(location)) {
-            case AttributeUse::Constant:
+            switch (header.ps.GetPixelImap(location)) {
+            case PixelImap::Constant:
                 Decorate(id, spv::Decoration::Flat);
                 break;
-            case AttributeUse::ScreenLinear:
-                Decorate(id, spv::Decoration::NoPerspective);
-                break;
-            case AttributeUse::Perspective:
+            case PixelImap::Perspective:
                 // Default
                 break;
+            case PixelImap::ScreenLinear:
+                Decorate(id, spv::Decoration::NoPerspective);
+                break;
             default:
                 UNREACHABLE_MSG("Unused attribute being fetched");
             }
@@ -1145,9 +1145,6 @@ private:
             switch (attribute) {
             case Attribute::Index::Position: {
                 if (stage == ShaderType::Fragment) {
-                    if (element == 3) {
-                        return {Constant(t_float, 1.0f), Type::Float};
-                    }
                     return {OpLoad(t_float, AccessElement(t_in_float, frag_coord, element)),
                             Type::Float};
                 }
diff --git a/src/video_core/shader/decode/other.cpp b/src/video_core/shader/decode/other.cpp
index 4944e9d69..e6edec459 100644
--- a/src/video_core/shader/decode/other.cpp
+++ b/src/video_core/shader/decode/other.cpp
@@ -11,12 +11,17 @@
 
 namespace VideoCommon::Shader {
 
+using std::move;
 using Tegra::Shader::ConditionCode;
 using Tegra::Shader::Instruction;
+using Tegra::Shader::IpaInterpMode;
 using Tegra::Shader::OpCode;
+using Tegra::Shader::PixelImap;
 using Tegra::Shader::Register;
 using Tegra::Shader::SystemVariable;
 
+using Index = Tegra::Shader::Attribute::Index;
+
 u32 ShaderIR::DecodeOther(NodeBlock& bb, u32 pc) {
     const Instruction instr = {program_code[pc]};
     const auto opcode = OpCode::Decode(instr);
@@ -213,27 +218,28 @@ u32 ShaderIR::DecodeOther(NodeBlock& bb, u32 pc) {
     }
     case OpCode::Id::IPA: {
         const bool is_physical = instr.ipa.idx && instr.gpr8.Value() != 0xff;
-
         const auto attribute = instr.attribute.fmt28;
-        const Tegra::Shader::IpaMode input_mode{instr.ipa.interp_mode.Value(),
-                                                instr.ipa.sample_mode.Value()};
+        const Index index = attribute.index;
 
         Node value = is_physical ? GetPhysicalInputAttribute(instr.gpr8)
-                                 : GetInputAttribute(attribute.index, attribute.element);
-        const Tegra::Shader::Attribute::Index index = attribute.index.Value();
-        const bool is_generic = index >= Tegra::Shader::Attribute::Index::Attribute_0 &&
-                                index <= Tegra::Shader::Attribute::Index::Attribute_31;
-        if (is_generic || is_physical) {
-            // TODO(Blinkhawk): There are cases where a perspective attribute use PASS.
-            // In theory by setting them as perspective, OpenGL does the perspective correction.
-            // A way must figured to reverse the last step of it.
-            if (input_mode.interpolation_mode == Tegra::Shader::IpaInterpMode::Multiply) {
-                value = Operation(OperationCode::FMul, PRECISE, value, GetRegister(instr.gpr20));
+                                 : GetInputAttribute(index, attribute.element);
+
+        // Code taken from Ryujinx.
+        if (index >= Index::Attribute_0 && index <= Index::Attribute_31) {
+            const u32 location = static_cast<u32>(index) - static_cast<u32>(Index::Attribute_0);
+            if (header.ps.GetPixelImap(location) == PixelImap::Perspective) {
+                Node position_w = GetInputAttribute(Index::Position, 3);
+                value = Operation(OperationCode::FMul, move(value), move(position_w));
             }
         }
-        value = GetSaturatedFloat(value, instr.ipa.saturate);
 
-        SetRegister(bb, instr.gpr0, value);
+        if (instr.ipa.interp_mode == IpaInterpMode::Multiply) {
+            value = Operation(OperationCode::FMul, move(value), GetRegister(instr.gpr20));
+        }
+
+        value = GetSaturatedFloat(move(value), instr.ipa.saturate);
+
+        SetRegister(bb, instr.gpr0, move(value));
         break;
     }
     case OpCode::Id::OUT_R: {