Detect RV300 and VC4 hardware and disable slow half float vertex on them

src/engine/renderer/tr_init.cpp

@@ -999,6 +999,15 @@ ScreenshotCmd screenshotPNGRegistration("screenshotPNG", ssFormat_t::SSF_PNG, "p
 			Log::Notice("%sMissing OpenGL extensions: %s", Color::ToString( Color::Red ), glConfig2.glMissingExtensionsString );
 		}
 
+		if ( glConfig2.halfFloatVertexAvailable )
+		{
+			Log::Notice("%sUsing half-float vertex format.", Color::ToString( Color::Green ));
+		}
+		else
+		{
+			Log::Notice("%sMissing half-float vertex format.", Color::ToString( Color::Red ));
+		}
+
 		if ( glConfig.hardwareType == glHardwareType_t::GLHW_R300 )
 		{
 			Log::Notice("%sUsing ATI R300 approximations.", Color::ToString( Color::Red ));

src/engine/sys/sdl_glimp.cpp

@@ -137,10 +137,18 @@ static Cvar::Cvar<bool> workaround_glDriver_mesa_ati_rv300_disableRgba16Blend(
 	"workaround.glDriver.mesa.ati.rv300.disableRgba16Blend",
 	"Disable misdetected RGBA16 on Mesa driver on RV300 hardware",
 	Cvar::NONE, true );
+static Cvar::Cvar<bool> workaround_glDriver_mesa_ati_rv300_useFloatVertex(
+	"workaround.glDriver.mesa.ati.rv300.useFloatVertex",
+	"Use float vertex instead of supported-but-slower half-float vertex on Mesa driver on ATI RV300 hardware",
+	Cvar::NONE, true );
 static Cvar::Cvar<bool> workaround_glDriver_mesa_ati_rv600_disableHyperZ(
 	"workaround.glDriver.mesa.ati.rv600.disableHyperZ",
 	"Disable Hyper-Z on Mesa driver on RV600 hardware",
 	Cvar::NONE, true );
+static Cvar::Cvar<bool> workaround_glDriver_mesa_broadcom_vc4_useFloatVertex(
+	"workaround.glDriver.mesa.broadcom.vc4.useFloatVertex",
+	"Use float vertex instead of supported-but-slower half-float vertex on Mesa driver on Broadcom VC4 hardware",
+	Cvar::NONE, true );
 static Cvar::Cvar<bool> workaround_glDriver_mesa_forceS3tc(
 	"workaround.glDriver.mesa.forceS3tc",
 	"Enable S3TC on Mesa even when libtxc-dxtn is not available",
@@ -2210,10 +2218,78 @@ static void GLimp_InitExtensions()
 		glConfig2.textureAnisotropy = std::max( std::min( r_ext_texture_filter_anisotropic.Get(), glConfig2.maxTextureAnisotropy ), 1.0f );
 	}
 
-	// VAO and VBO
-	// made required in OpenGL 3.0
-	glConfig2.halfFloatVertexAvailable = LOAD_EXTENSION_WITH_TEST(
-		ExtFlag_CORE, ARB_half_float_vertex, r_arb_half_float_vertex.Get() );
+	/* We call RV300 the first generation of R300 cards, to make a difference
+	with RV400 and RV500 cards that are also supported by the Mesa r300 driver.
+
+	Mesa r300 implements half-float vertex for the RV300 hardware generation,
+	but it is likely emulated and it is very slow. We better use float vertex
+	instead. */
+	{
+		bool halfFloatVertexEnabled = r_arb_half_float_vertex.Get();
+
+		if ( halfFloatVertexEnabled && glConfig2.driverVendor == glDriverVendor_t::MESA )
+		{
+			if ( glConfig2.hardwareVendor == glHardwareVendor_t::ATI )
+			{
+				bool foundRv300 = false;
+
+				std::string cardName = "";
+
+				static const std::string codenames[] = {
+					"R300", "R350", "R360",
+					"RV350", "RV360", "RV370", "RV380",
+				};
+
+				for ( auto& codename : codenames )
+				{
+					cardName = Str::Format( "ATI %s", codename );
+
+					if ( Str::IsPrefix( cardName, glConfig.renderer_string ) )
+					{
+						foundRv300 = true;
+						break;
+					}
+				}
+
+				/* The RV300 generation only has 64 ALU instructions while RV400 and RV500
+				have 512 of them, so we can also use that value to detect RV300. */
+				if ( !foundRv300 )
+				{
+					if ( glConfig.hardwareType == glHardwareType_t::GLHW_R300
+						&& glConfig2.maxAluInstructions == 64 )
+					{
+						cardName = "unknown ATI RV3xx";
+						foundRv300 = true;
+					}
+				}
+
+				if ( foundRv300 && workaround_glDriver_mesa_ati_rv300_useFloatVertex.Get() )
+				{
+					logger.Notice( "Found slow Mesa half-float vertex implementation with %s hardware, disabling ARB_half_float_vertex.", cardName );
+					halfFloatVertexEnabled = false;
+				}
+			}
+			else if ( glConfig2.hardwareVendor == glHardwareVendor_t::BROADCOM )
+			{
+				bool foundVc4 = Str::IsPrefix( "VC4 ", glConfig.renderer_string );
+
+				if ( foundVc4 && workaround_glDriver_mesa_broadcom_vc4_useFloatVertex.Get() )
+				{
+					logger.Notice( "Found slow Mesa half-float vertex implementation with Broadcom VC4 hardware, disabling ARB_half_float_vertex." );
+					halfFloatVertexEnabled = false;
+				}
+			}
+		}
+
+		// VAO and VBO
+		// made required in OpenGL 3.0
+		glConfig2.halfFloatVertexAvailable = LOAD_EXTENSION_WITH_TEST( ExtFlag_CORE, ARB_half_float_vertex, halfFloatVertexEnabled );
+
+		if ( !halfFloatVertexEnabled )
+		{
+			logger.Notice( "Missing half-float vertex, using float vertex instead." );
+		}
+	}
 
 	if ( !workaround_glExtension_missingArbFbo_useExtFbo.Get() )
 	{
@@ -2536,7 +2612,9 @@ bool GLimp_Init()
 	Cvar::Latch( workaround_glDriver_amd_adrenalin_disableBindlessTexture );
 	Cvar::Latch( workaround_glDriver_amd_oglp_disableBindlessTexture );
 	Cvar::Latch( workaround_glDriver_mesa_ati_rv300_disableRgba16Blend );
+	Cvar::Latch( workaround_glDriver_mesa_ati_rv300_useFloatVertex );
 	Cvar::Latch( workaround_glDriver_mesa_ati_rv600_disableHyperZ );
+	Cvar::Latch( workaround_glDriver_mesa_broadcom_vc4_useFloatVertex );
 	Cvar::Latch( workaround_glDriver_mesa_forceS3tc );
 	Cvar::Latch( workaround_glDriver_mesa_intel_gma3_forceFragmentShader );
 	Cvar::Latch( workaround_glDriver_mesa_intel_gma3_stubOcclusionQuery );