Fragment shader: Don't error on bad blend eqs, instead use default eq (add)

GPU/Common/FragmentShaderGenerator.cpp

@@ -1118,7 +1118,7 @@ bool GenerateFragmentShader(const FShaderID &id, char *buffer, const ShaderLangu
 				WRITE(p, "  v.rgb = abs(v.rgb - destColor.rgb);\n");
 				break;
 			default:
-				*errorString = "Bad replace blend eq";
+				*errorString = StringFromFormat("Bad replace blend eq: %d", (int)replaceBlendEq);
 				return false;
 			}
 		}

GPU/Common/GPUStateUtils.cpp

@@ -293,11 +293,10 @@ ReplaceBlendType ReplaceBlendWithShader(GEBufferFormat bufferFormat) {
 	case GE_BLENDMODE_MUL_AND_ADD:
 	case GE_BLENDMODE_MUL_AND_SUBTRACT:
 	case GE_BLENDMODE_MUL_AND_SUBTRACT_REVERSE:
-		// Handled below.
+		// Other blend equations simply don't blend on hardware.
 		break;
 
 	default:
-		// Other blend equations simply don't blend on hardware.
 		return REPLACE_BLEND_NO;
 	}
 
@@ -849,6 +848,8 @@ static const BlendEq eqLookupNoMinMax[] = {
 	BlendEq::ADD,			// GE_BLENDMODE_MIN
 	BlendEq::ADD,			// GE_BLENDMODE_MAX
 	BlendEq::ADD,			// GE_BLENDMODE_ABSDIFF
+	BlendEq::ADD,
+	BlendEq::ADD,
 };
 
 static const BlendEq eqLookup[] = {
@@ -858,6 +859,8 @@ static const BlendEq eqLookup[] = {
 	BlendEq::MIN,			// GE_BLENDMODE_MIN
 	BlendEq::MAX,			// GE_BLENDMODE_MAX
 	BlendEq::MAX,			// GE_BLENDMODE_ABSDIFF
+	BlendEq::ADD,
+	BlendEq::ADD,
 };
 
 static BlendFactor toDualSource(BlendFactor blendfunc) {

GPU/Common/ShaderId.cpp

@@ -277,6 +277,13 @@ bool FragmentIdNeedsFramebufferRead(const FShaderID &id) {
 		(ReplaceBlendType)id.Bits(FS_BIT_REPLACE_BLEND, 3) == REPLACE_BLEND_READ_FRAMEBUFFER;
 }
 
+inline u32 SanitizeBlendMode(GEBlendMode mode) {
+	if (mode > GE_BLENDMODE_ABSDIFF)
+		return GE_BLENDMODE_MUL_AND_ADD;  // Not sure what the undefined modes are.
+	else
+		return mode;
+}
+
 // Here we must take all the bits of the gstate that determine what the fragment shader will
 // look like, and concatenate them together into an ID.
 void ComputeFragmentShaderID(FShaderID *id_out, const ComputedPipelineState &pipelineState, const Draw::Bugs &bugs) {
@@ -371,7 +378,7 @@ void ComputeFragmentShaderID(FShaderID *id_out, const ComputedPipelineState &pip
 			// 3 bits.
 			id.SetBits(FS_BIT_REPLACE_BLEND, 3, replaceBlend);
 			// 11 bits total.
-			id.SetBits(FS_BIT_BLENDEQ, 3, gstate.getBlendEq());
+			id.SetBits(FS_BIT_BLENDEQ, 3, SanitizeBlendMode(gstate.getBlendEq()));
 			id.SetBits(FS_BIT_BLENDFUNC_A, 4, gstate.getBlendFuncA());
 			id.SetBits(FS_BIT_BLENDFUNC_B, 4, gstate.getBlendFuncB());
 		}