GPU/OpenGL: Use shader instead of framebuffer blit

src/core/gpu_hw_opengl.cpp

@@ -728,6 +728,21 @@ bool GPU_HW_OpenGL::CompilePrograms()
     m_downsample_program = std::move(*prog);
   }
 
+  prog = shader_cache.GetProgram(shadergen.GenerateUVQuadVertexShader(), {}, shadergen.GenerateSampleFragmentShader(),
+                                 [this, use_binding_layout](GL::Program& prog) {
+                                   if (!IsGLES() && !use_binding_layout)
+                                     prog.BindFragData(0, "o_col0");
+                                 });
+  if (!prog)
+    return false;
+
+  if (!use_binding_layout)
+  {
+    prog->Bind();
+    prog->Uniform1i("samp0", 0);
+  }
+  m_blit_program = std::move(*prog);
+
   UPDATE_PROGRESS();
 #undef UPDATE_PROGRESS
 
@@ -1165,12 +1180,12 @@ void GPU_HW_OpenGL::UpdateVRAM(u32 x, u32 y, u32 width, u32 height, const void*
       const u32 scaled_x = x * m_resolution_scale;
       const u32 scaled_y = y * m_resolution_scale;
       const u32 scaled_flipped_y = m_vram_texture.GetHeight() - scaled_y - scaled_height;
-      glDisable(GL_SCISSOR_TEST);
-      m_vram_encoding_texture.BindFramebuffer(GL_READ_FRAMEBUFFER);
-      glBlitFramebuffer(x, flipped_y, x + width, flipped_y + height, scaled_x, scaled_flipped_y,
-                        scaled_x + scaled_width, scaled_flipped_y + scaled_height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
-      glEnable(GL_SCISSOR_TEST);
+
+      BlitTexture(m_vram_encoding_texture, x, flipped_y, width, height, scaled_x, scaled_flipped_y, scaled_width,
+                  scaled_height);
     }
+
+    RestoreGraphicsAPIState();
   }
 }
 
@@ -1201,6 +1216,7 @@ void GPU_HW_OpenGL::CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 wid
                dst_bounds_scaled.GetWidth(), dst_bounds_scaled.GetHeight());
     m_vram_read_texture.Bind();
     m_vram_copy_program.Bind();
+    glBindVertexArray(m_attributeless_vao_id);
     glDrawArrays(GL_TRIANGLES, 0, 3);
 
     RestoreGraphicsAPIState();
@@ -1241,21 +1257,77 @@ void GPU_HW_OpenGL::CopyVRAM(u32 src_x, u32 src_y, u32 dst_x, u32 dst_y, u32 wid
   }
   else
   {
-    // glBlitFramebufer with same source/destination should be legal, but on Mali (at least Bifrost) it breaks.
-    // So, blit from the shadow texture, like in the other renderers.
     if (src_dirty)
       UpdateVRAMReadTexture();
 
-    glDisable(GL_SCISSOR_TEST);
-    m_vram_read_texture.BindFramebuffer(GL_READ_FRAMEBUFFER);
-    glBlitFramebuffer(src_x, src_y, src_x + width, src_y + height, dst_x, dst_y, dst_x + width, dst_y + height,
-                      GL_COLOR_BUFFER_BIT, GL_NEAREST);
-    glEnable(GL_SCISSOR_TEST);
+    CopyTexture(m_vram_texture, m_vram_fbo_id, m_vram_read_texture, src_x, src_y, dst_x, dst_y, width, height);
   }
 
   IncludeVRAMDirtyRectangle(dst_bounds);
 }
 
+void GPU_HW_OpenGL::CopyTexture(GL::Texture& dest, GLuint dest_fbo, GL::Texture& src, u32 src_x, u32 src_y, u32 dst_x,
+                                u32 dst_y, u32 width, u32 height)
+{
+  if (src.IsMultisampled())
+  {
+    // The MSAA case still needs framebuffer blits.
+    dest.BindFramebuffer(GL_DRAW_FRAMEBUFFER);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, dest_fbo);
+    glDisable(GL_SCISSOR_TEST);
+    glBlitFramebuffer(src_x, src_y, src_x + width, src_y + height, dst_x, dst_y, dst_x + width, dst_y + height,
+                      GL_COLOR_BUFFER_BIT, GL_NEAREST);
+    glEnable(GL_SCISSOR_TEST);
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, dest_fbo);
+    return;
+  }
+
+  if (GLAD_GL_VERSION_4_3)
+  {
+    glCopyImageSubData(src.GetGLId(), src.GetGLTarget(), 0, src_x, src_y, 0, dest.GetGLId(), src.GetGLTarget(), 0,
+                       dst_x, dst_y, 0, width, height, 1);
+  }
+  else if (GLAD_GL_EXT_copy_image)
+  {
+    glCopyImageSubDataEXT(src.GetGLId(), src.GetGLTarget(), 0, src_x, src_y, 0, dest.GetGLId(), src.GetGLTarget(), 0,
+                          dst_x, dst_y, 0, width, height, 1);
+  }
+  else if (GLAD_GL_OES_copy_image)
+  {
+    glCopyImageSubDataOES(src.GetGLId(), src.GetGLTarget(), 0, src_x, src_y, 0, dest.GetGLId(), src.GetGLTarget(), 0,
+                          dst_x, dst_y, 0, width, height, 1);
+  }
+  else
+  {
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, dest_fbo);
+    BlitTexture(src, src_x, src_y, width, height, dst_x, dst_y, width, height);
+    RestoreGraphicsAPIState();
+  }
+}
+
+void GPU_HW_OpenGL::BlitTexture(GL::Texture& src, u32 src_x, u32 src_y, u32 src_width, u32 src_height, u32 dst_x,
+                                u32 dst_y, u32 dst_width, u32 dst_height)
+{
+  // But a copy shader is probably better on mobile drivers.
+  const float uniforms[4] = {
+    static_cast<float>(src_x) / static_cast<float>(src.GetWidth()),
+    static_cast<float>(src_y) / static_cast<float>(src.GetHeight()),
+    static_cast<float>(src_x + src_width) / static_cast<float>(src.GetWidth()),
+    static_cast<float>(src_y + src_height) / static_cast<float>(src.GetHeight()),
+  };
+  UploadUniformBuffer(uniforms, sizeof(uniforms));
+
+  glDisable(GL_SCISSOR_TEST);
+  glDisable(GL_BLEND);
+  SetDepthFunc(GL_ALWAYS);
+
+  glViewport(dst_x, dst_y, dst_width, dst_height);
+  src.Bind();
+  m_blit_program.Bind();
+  glBindVertexArray(m_attributeless_vao_id);
+  glDrawArrays(GL_TRIANGLES, 0, 3);
+}
+
 void GPU_HW_OpenGL::UpdateVRAMReadTexture()
 {
   const auto scaled_rect = m_vram_dirty_rect * m_resolution_scale;
@@ -1263,32 +1335,8 @@ void GPU_HW_OpenGL::UpdateVRAMReadTexture()
   const u32 height = scaled_rect.GetHeight();
   const u32 x = scaled_rect.left;
   const u32 y = m_vram_texture.GetHeight() - scaled_rect.top - height;
-  const bool multisampled = m_vram_texture.IsMultisampled();
 
-  if (!multisampled && GLAD_GL_VERSION_4_3)
-  {
-    glCopyImageSubData(m_vram_texture.GetGLId(), m_vram_texture.GetGLTarget(), 0, x, y, 0,
-                       m_vram_read_texture.GetGLId(), m_vram_texture.GetGLTarget(), 0, x, y, 0, width, height, 1);
-  }
-  else if (!multisampled && GLAD_GL_EXT_copy_image)
-  {
-    glCopyImageSubDataEXT(m_vram_texture.GetGLId(), m_vram_texture.GetGLTarget(), 0, x, y, 0,
-                          m_vram_read_texture.GetGLId(), m_vram_texture.GetGLTarget(), 0, x, y, 0, width, height, 1);
-  }
-  else if (!multisampled && GLAD_GL_OES_copy_image)
-  {
-    glCopyImageSubDataOES(m_vram_texture.GetGLId(), m_vram_texture.GetGLTarget(), 0, x, y, 0,
-                          m_vram_read_texture.GetGLId(), m_vram_texture.GetGLTarget(), 0, x, y, 0, width, height, 1);
-  }
-  else
-  {
-    m_vram_read_texture.BindFramebuffer(GL_DRAW_FRAMEBUFFER);
-    glBindFramebuffer(GL_READ_FRAMEBUFFER, m_vram_fbo_id);
-    glDisable(GL_SCISSOR_TEST);
-    glBlitFramebuffer(x, y, x + width, y + height, x, y, x + width, y + height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
-    glEnable(GL_SCISSOR_TEST);
-    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, m_vram_fbo_id);
-  }
+  CopyTexture(m_vram_read_texture, m_vram_read_texture.GetGLFramebufferID(), m_vram_texture, x, y, x, y, width, height);
 
   GPU_HW::UpdateVRAMReadTexture();
 }

src/core/gpu_hw_opengl.h

@@ -76,6 +76,10 @@ private:
   bool BlitVRAMReplacementTexture(const TextureReplacementTexture* tex, u32 dst_x, u32 dst_y, u32 width, u32 height);
   void DownsampleFramebuffer(GL::Texture& source, u32 left, u32 top, u32 width, u32 height);
   void DownsampleFramebufferBoxFilter(GL::Texture& source, u32 left, u32 top, u32 width, u32 height);
+  void CopyTexture(GL::Texture& dest, GLuint dest_fbo, GL::Texture& src, u32 src_x, u32 src_y, u32 dst_x, u32 dst_y,
+                   u32 width, u32 height);
+  void BlitTexture(GL::Texture& src, u32 src_x, u32 src_y, u32 src_width, u32 src_height, u32 dst_x, u32 dst_y,
+                   u32 dst_width, u32 dst_height);
 
   // downsample texture - used for readbacks at >1xIR.
   GL::Texture m_vram_texture;
@@ -104,6 +108,7 @@ private:
   GL::Program m_vram_write_program;
   GL::Program m_vram_copy_program;
   GL::Program m_vram_update_depth_program;
+  GL::Program m_blit_program;
 
   u32 m_uniform_buffer_alignment = 1;
   u32 m_texture_stream_buffer_size = 0;

src/core/shadergen.cpp

@@ -617,3 +617,19 @@ std::string ShaderGen::GenerateCopyFragmentShader()
 
   return ss.str();
 }
+
+std::string ShaderGen::GenerateSampleFragmentShader()
+{
+  std::stringstream ss;
+  WriteHeader(ss);
+  DeclareTexture(ss, "samp0", 0);
+  DeclareFragmentEntryPoint(ss, 0, 1, {}, false, 1);
+
+  ss << R"(
+{
+  o_col0 = SAMPLE_TEXTURE(samp0, v_tex0);
+}
+)";
+
+  return ss.str();
+}

src/core/shadergen.h

@@ -16,6 +16,7 @@ public:
   std::string GenerateUVQuadVertexShader();
   std::string GenerateFillFragmentShader();
   std::string GenerateCopyFragmentShader();
+  std::string GenerateSampleFragmentShader();
 
 protected:
   ALWAYS_INLINE bool IsVulkan() const { return (m_render_api == HostDisplay::RenderAPI::Vulkan); }