GPU/HW: Clear alpha channel in opaque replacements

This is the value for bit15 in the framebuffer. Silent Hill
needs it to be zero, I'm not aware of anything that needs
specific values yet. If it did, we'd need a different dumping
technique.

src/core/gpu_hw_shadergen.cpp

@@ -1880,11 +1880,14 @@ std::string GPU_HW_ShaderGen::GenerateReplacementMergeFragmentShader(bool semitr
     o_col0.a = (color.a <= 0.95f) ? 1.0f : 0.0f;
     o_col0.a = VECTOR_EQ(color, float4(0.0, 0.0, 0.0, 0.0)) ? 0.0f : o_col0.a;
   #else
+    // Map anything with an alpha below 0.5 to transparent.
     // Leave (0,0,0,0) as 0000 for opaque replacements for cutout alpha.
-    o_col0.a = color.a;
+    o_col0.rgb = lerp(o_col0.rgb, float3(0.0, 0.0, 0.0), float(color.a < 0.5));
 
-    // Map anything with an alpha below 0.5 to transparent.
-    o_col0 = lerp(o_col0, float4(0.0, 0.0, 0.0, 0.0), float(o_col0.a < 0.5));
+    // Clear alpha channel. This is the value for bit15 in the framebuffer.
+    // Silent Hill needs it to be zero, I'm not aware of anything that needs
+    // specific values yet. If it did, we'd need a different dumping technique.
+    o_col0.a = 0.0;
   #endif
 }
 )";