From 27bc65fc2ada7d5c34ce7d4f8219f0c9dcddcc8f Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <mclaughc@outlook.com>
Date: Fri, 4 Oct 2019 23:21:20 +1000
Subject: [PATCH] GPU: Use BitField sign extending for position

---
 src/core/gpu.cpp    |  4 ++--
 src/core/gpu.h      | 15 ++-------------
 src/core/gpu_hw.cpp | 10 +++++-----
 3 files changed, 9 insertions(+), 20 deletions(-)

diff --git a/src/core/gpu.cpp b/src/core/gpu.cpp
index 8f9bf4460..e28614bb8 100644
--- a/src/core/gpu.cpp
+++ b/src/core/gpu.cpp
@@ -477,8 +477,8 @@ void GPU::WriteGP0(u32 value)
 
       case 0xE5: // Set drawing offset
       {
-        m_drawing_offset.x = S11ToS32(param & UINT32_C(0x7FF));
-        m_drawing_offset.y = S11ToS32((param >> 11) & UINT32_C(0x7FF));
+        m_drawing_offset.x = SignExtendN<11, u32>(param & UINT32_C(0x7FF));
+        m_drawing_offset.y = SignExtendN<11, u32>((param >> 11) & UINT32_C(0x7FF));
         Log_DebugPrintf("Set drawing offset (%d, %d)", m_drawing_offset.x, m_drawing_offset.y);
       }
       break;
diff --git a/src/core/gpu.h b/src/core/gpu.h
index 94288be60..4f10ba848 100644
--- a/src/core/gpu.h
+++ b/src/core/gpu.h
@@ -61,14 +61,6 @@ public:
   void Execute(TickCount ticks);
 
 protected:
-  static constexpr s32 S11ToS32(u32 value)
-  {
-    if (value & (UINT16_C(1) << 10))
-      return static_cast<s32>(UINT32_C(0xFFFFF800) | value);
-    else
-      return value;
-  }
-
   // Helper/format conversion functions.
   static constexpr u32 RGBA5551ToRGBA8888(u16 color)
   {
@@ -164,11 +156,8 @@ protected:
   {
     u32 bits;
 
-    BitField<u32, u32, 0, 11> x_s11;
-    BitField<u32, u32, 16, 11> y_s11;
-
-    s32 x() const { return S11ToS32(x_s11); }
-    s32 y() const { return S11ToS32(y_s11); }
+    BitField<u32, s32, 0, 11> x;
+    BitField<u32, s32, 16, 11> y;
   };
 
   struct DebugOptions
diff --git a/src/core/gpu_hw.cpp b/src/core/gpu_hw.cpp
index 1f8bcb287..6e0310a16 100644
--- a/src/core/gpu_hw.cpp
+++ b/src/core/gpu_hw.cpp
@@ -41,8 +41,8 @@ void GPU_HW::LoadVertices(RenderCommand rc, u32 num_vertices)
         hw_vert.color = (shaded && i > 0) ? (m_GP0_command[buffer_pos++] & UINT32_C(0x00FFFFFF)) : first_color;
 
         const VertexPosition vp{m_GP0_command[buffer_pos++]};
-        hw_vert.x = vp.x();
-        hw_vert.y = vp.y();
+        hw_vert.x = vp.x;
+        hw_vert.y = vp.y;
         hw_vert.texpage = texpage;
 
         if (textured)
@@ -73,8 +73,8 @@ void GPU_HW::LoadVertices(RenderCommand rc, u32 num_vertices)
       const bool textured = rc.texture_enable;
       const u32 color = rc.color_for_first_vertex;
       const VertexPosition vp{m_GP0_command[buffer_pos++]};
-      const s32 pos_left = vp.x();
-      const s32 pos_top = vp.y();
+      const s32 pos_left = vp.x;
+      const s32 pos_top = vp.y;
       const auto [tex_left, tex_top] =
         HWVertex::DecodeTexcoord(rc.texture_enable ? Truncate16(m_GP0_command[buffer_pos++]) : 0);
       s32 rectangle_width;
@@ -128,7 +128,7 @@ void GPU_HW::LoadVertices(RenderCommand rc, u32 num_vertices)
       {
         const u32 color = (shaded && i > 0) ? (m_GP0_command[buffer_pos++] & UINT32_C(0x00FFFFFF)) : first_color;
         const VertexPosition vp{m_GP0_command[buffer_pos++]};
-        m_batch.vertices.push_back(HWVertex{vp.x(), vp.y(), color});
+        m_batch.vertices.push_back(HWVertex{vp.x.GetValue(), vp.y.GetValue(), color});
       }
     }
     break;