gsdx-tc: use a single shader pass to convert texture in 8 bits format

It might save a couple of fps

Add a define to test the perf if we keep only the blue channel. It brokes
the code in Prince Of Persia that use the Red/Green channel... Maybe the
speed hack :( Or find a way to replace all if with a lookup table

Note: it is only supported on OpenGL currently

plugins/GSdx/GSDevice.h

@@ -28,6 +28,14 @@
 
 #pragma pack(push, 1)
 
+class ConvertConstantBuffer
+{
+public:
+	GSVector4i ScalingFactor;
+
+	ConvertConstantBuffer() {memset(this, 0, sizeof(*this));}
+};
+
 class MergeConstantBuffer
 {
 public:

plugins/GSdx/GSDeviceOGL.cpp

@@ -39,6 +39,7 @@ static const uint32 g_merge_cb_index      = 10;
 static const uint32 g_interlace_cb_index  = 11;
 static const uint32 g_shadeboost_cb_index = 12;
 static const uint32 g_fx_cb_index         = 14;
+static const uint32 g_convert_index       = 15;
 
 bool GSDeviceOGL::m_debug_gl_call = false;
 int  GSDeviceOGL::s_n = 0;
@@ -103,6 +104,7 @@ GSDeviceOGL::~GSDeviceOGL()
 	delete m_convert.dss;
 	delete m_convert.dss_write;
 	delete m_convert.bs;
+	delete m_convert.cb;
 
 	// Clean m_fxaa
 	delete m_fxaa.cb;
@@ -242,6 +244,12 @@ bool GSDeviceOGL::Create(GSWnd* wnd)
 	// ****************************************************************
 	// convert
 	// ****************************************************************
+	m_convert.cb = new GSUniformBufferOGL(g_convert_index, sizeof(ConvertConstantBuffer));
+	// Upload once and forget about it
+	ConvertConstantBuffer cb;
+	cb.ScalingFactor = GSVector4i(theApp.GetConfig("nativeres", 0) ? 1 : theApp.GetConfig("upscale_multiplier", 2));
+	m_convert.cb->upload(&cb);
+
 	m_convert.vs = m_shader->Compile("convert.glsl", "vs_main", GL_VERTEX_SHADER, convert_glsl);
 	for(size_t i = 0; i < countof(m_convert.ps); i++)
 		m_convert.ps[i] = m_shader->Compile("convert.glsl", format("ps_main%d", i), GL_FRAGMENT_SHADER, convert_glsl);

plugins/GSdx/GSDeviceOGL.h

@@ -504,6 +504,7 @@ class GSDeviceOGL : public GSDevice
 		GSDepthStencilOGL* dss;
 		GSDepthStencilOGL* dss_write;
 		GSBlendStateOGL* bs;
+		GSUniformBufferOGL* cb;
 	} m_convert;
 
 	struct {

plugins/GSdx/GSTextureCache.cpp

@@ -820,8 +820,9 @@ GSTextureCache::Source* GSTextureCache::CreateSource(const GIFRegTEX0& TEX0, con
 		// Shader 11 convert depth to color
 		// Shader 14 convert 32 bits color to 8 bits color
 		int shader = dst->m_type != RenderTarget ? 11 : 0;
+		bool is_8bits = TEX0.PSM == PSM_PSMT8 && IsOpenGL();
 
-		if (TEX0.PSM == PSM_PSMT8) {
+		if (is_8bits) {
 			GL_INS("Reading RT as a packed-indexed 8 bits format");
 			shader = 14; // ask a conversion to 8 bits format
 		}
@@ -847,29 +848,15 @@ GSTextureCache::Source* GSTextureCache::CreateSource(const GIFRegTEX0& TEX0, con
 		}
 
 
-		// Unscale 8 bits textures, quality won't be nice but format is really awful
-		// Code won't be compatible with MSAA but it is a DX issue
-		if (TEX0.PSM == PSM_PSMT8) {
-			GSVector2 old_scale = dst->m_texture->GetScale();
-
-			if (old_scale != GSVector2(1.0f, 1.0f)) {
-				GSVector2i size = dst->m_texture->GetSize();
-				tmp = dst->m_texture;
-
-				dst->m_texture = m_renderer->m_dev->CreateRenderTarget(size.x, size.y, false);
-
-				GSVector4 sRect(0.0, 0.0, old_scale.x, old_scale.y);
-				GSVector4 dRect(0.0, 0.0, size.x, size.y);
-				m_renderer->m_dev->StretchRect(tmp, sRect, dst->m_texture, dRect, 0, false);
-
-				dst->m_texture->SetScale(GSVector2(1.0f, 1.0f));
-			}
-		}
-
 		// do not round here!!! if edge becomes a black pixel and addressing mode is clamp => everything outside the clamped area turns into black (kh2 shadows)
 
 		int w = (int)(dst->m_texture->GetScale().x * tw);
 		int h = (int)(dst->m_texture->GetScale().y * th);
+		if (is_8bits) {
+			// Unscale 8 bits textures, quality won't be nice but format is really awful
+			w = tw;
+			h = th;
+		}
 
 		GSVector2i dstsize = dst->m_texture->GetSize();
 
@@ -955,18 +942,21 @@ GSTextureCache::Source* GSTextureCache::CreateSource(const GIFRegTEX0& TEX0, con
 		// FIXME: The scaling will create a bad offset. For example if texture coordinate start at 0.5 (pixel 0)
 		// At 2x it will become 0.5/128 * 256 = 1 (pixel 1)
 
-		if(w > dstsize.x)
+		if (!is_8bits) {
-		{
+			// 8 bits handling is special due to unscaling. It is better to not execute this code
-			scale.x = (float)dstsize.x / tw;
+			if (w > dstsize.x)
-			dRect.z = (float)dstsize.x * scale.x / dst->m_texture->GetScale().x;
+			{
-			w = dstsize.x;
+				scale.x = (float)dstsize.x / tw;
-		}
+				dRect.z = (float)dstsize.x * scale.x / dst->m_texture->GetScale().x;
+				w = dstsize.x;
+			}
 
-		if(h > dstsize.y)
+			if (h > dstsize.y)
-		{
+			{
-			scale.y = (float)dstsize.y / th;
+				scale.y = (float)dstsize.y / th;
-			dRect.w = (float)dstsize.y * scale.y / dst->m_texture->GetScale().y;
+				dRect.w = (float)dstsize.y * scale.y / dst->m_texture->GetScale().y;
-			h = dstsize.y;
+				h = dstsize.y;
+			}
 		}
 
 		GSVector4 sRect(0, 0, w, h);

plugins/GSdx/res/glsl/convert.glsl

@@ -70,6 +70,11 @@ layout(bindless_sampler, location = 0) uniform sampler2D TextureSampler;
 layout(binding = 0) uniform sampler2D TextureSampler;
 #endif
 
+layout(std140, binding = 15) uniform cb15
+{
+    ivec4 ScalingFactor;
+};
+
 vec4 sample_c()
 {
     return texture(TextureSampler, PSin_t );
@@ -199,6 +204,15 @@ void ps_main13()
 #ifdef ps_main14
 void ps_main14()
 {
+
+    // Potential speed optimization. There is a high probability that
+    // game only want to extract a single channel (blue). It will allow
+    // to remove most of the conditional operation and yield a +2/3 fps
+    // boost on MGS3
+    //
+    // Hypothesis wrong in Prince of Persia ... Seriously WTF !
+//#define ONLY_BLUE;
+
     // Convert a RGBA texture into a 8 bits packed texture
     // Input column: 8x2 RGBA pixels
     // 0: 8 RGBA
@@ -208,7 +222,6 @@ void ps_main14()
     // 1: 8 R | 8 B
     // 2: 8 G | 8 A
     // 3: 8 G | 8 A
-
     float c;
 
     uvec2 sel = uvec2(gl_FragCoord.xy) % uvec2(16u, 16u);
@@ -218,15 +231,20 @@ void ps_main14()
     int txN  = tb.x | (int(gl_FragCoord.x) & 7);
     int txH  = tb.x | ((int(gl_FragCoord.x) + 4) & 7);
 
+    txN *= ScalingFactor.x;
+    txH *= ScalingFactor.x;
+    ty  *= ScalingFactor.y;
+
+    // TODO investigate texture gather
     vec4 cN = texelFetch(TextureSampler, ivec2(txN, ty), 0);
     vec4 cH = texelFetch(TextureSampler, ivec2(txH, ty), 0);
 
-    // Potential speed optimization. There is a high probability that
-    // game only want to extract a single channel (blue). It will allow
-    // to remove the sel.x condition check
 
     if ((sel.y & 4u) == 0u) {
         // Column 0 and 2
+#ifdef ONLY_BLUE
+        c = cN.b;
+#else
         if ((sel.y & 3u) < 2u) {
             // first 2 lines of the col
             if (sel.x < 8u)
@@ -239,7 +257,11 @@ void ps_main14()
             else
                 c = cH.a;
         }
+#endif
     } else {
+#ifdef ONLY_BLUE
+        c = cH.b;
+#else
         // Column 1 and 3
         if ((sel.y & 3u) < 2u) {
             // first 2 lines of the col
@@ -253,6 +275,7 @@ void ps_main14()
             else
                 c = cN.a;
         }
+#endif
     }
 
 

plugins/GSdx/res/glsl_source.h

@@ -95,6 +95,11 @@ static const char* convert_glsl =
 	"layout(binding = 0) uniform sampler2D TextureSampler;\n"
 	"#endif\n"
 	"\n"
+	"layout(std140, binding = 15) uniform cb15\n"
+	"{\n"
+	"    ivec4 ScalingFactor;\n"
+	"};\n"
+	"\n"
 	"vec4 sample_c()\n"
 	"{\n"
 	"    return texture(TextureSampler, PSin_t );\n"
@@ -224,6 +229,15 @@ static const char* convert_glsl =
 	"#ifdef ps_main14\n"
 	"void ps_main14()\n"
 	"{\n"
+	"\n"
+	"    // Potential speed optimization. There is a high probability that\n"
+	"    // game only want to extract a single channel (blue). It will allow\n"
+	"    // to remove most of the conditional operation and yield a +2/3 fps\n"
+	"    // boost on MGS3\n"
+	"    //\n"
+	"    // Hypothesis wrong in Prince of Persia ... Seriously WTF !\n"
+	"//#define ONLY_BLUE;\n"
+	"\n"
 	"    // Convert a RGBA texture into a 8 bits packed texture\n"
 	"    // Input column: 8x2 RGBA pixels\n"
 	"    // 0: 8 RGBA\n"
@@ -233,7 +247,6 @@ static const char* convert_glsl =
 	"    // 1: 8 R | 8 B\n"
 	"    // 2: 8 G | 8 A\n"
 	"    // 3: 8 G | 8 A\n"
-	"\n"
 	"    float c;\n"
 	"\n"
 	"    uvec2 sel = uvec2(gl_FragCoord.xy) % uvec2(16u, 16u);\n"
@@ -243,15 +256,20 @@ static const char* convert_glsl =
 	"    int txN  = tb.x | (int(gl_FragCoord.x) & 7);\n"
 	"    int txH  = tb.x | ((int(gl_FragCoord.x) + 4) & 7);\n"
 	"\n"
+	"    txN *= ScalingFactor.x;\n"
+	"    txH *= ScalingFactor.x;\n"
+	"    ty  *= ScalingFactor.y;\n"
+	"\n"
+	"    // TODO investigate texture gather\n"
 	"    vec4 cN = texelFetch(TextureSampler, ivec2(txN, ty), 0);\n"
 	"    vec4 cH = texelFetch(TextureSampler, ivec2(txH, ty), 0);\n"
 	"\n"
-	"    // Potential speed optimization. There is a high probability that\n"
-	"    // game only want to extract a single channel (blue). It will allow\n"
-	"    // to remove the sel.x condition check\n"
 	"\n"
 	"    if ((sel.y & 4u) == 0u) {\n"
 	"        // Column 0 and 2\n"
+	"#ifdef ONLY_BLUE\n"
+	"        c = cN.b;\n"
+	"#else\n"
 	"        if ((sel.y & 3u) < 2u) {\n"
 	"            // first 2 lines of the col\n"
 	"            if (sel.x < 8u)\n"
@@ -264,7 +282,11 @@ static const char* convert_glsl =
 	"            else\n"
 	"                c = cH.a;\n"
 	"        }\n"
+	"#endif\n"
 	"    } else {\n"
+	"#ifdef ONLY_BLUE\n"
+	"        c = cH.b;\n"
+	"#else\n"
 	"        // Column 1 and 3\n"
 	"        if ((sel.y & 3u) < 2u) {\n"
 	"            // first 2 lines of the col\n"
@@ -278,6 +300,7 @@ static const char* convert_glsl =
 	"            else\n"
 	"                c = cN.a;\n"
 	"        }\n"
+	"#endif\n"
 	"    }\n"
 	"\n"
 	"\n"