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gl_shader_decompiler: Use an if based cbuf indexing for broken drivers

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The following code is broken on AMD's proprietary GLSL compiler:
```glsl
uint idx = ...;
vec4 values = ...;
float some_value = values[idx & 3];
```

It index the wrong components, to fix this the following pessimized code
is emitted when that bug is present:
```glsl
uint idx = ...;
vec4 values = ...;
float some_value;
if ((idx & 3) == 0) some_value = values.x;
if ((idx & 3) == 1) some_value = values.y;
if ((idx & 3) == 2) some_value = values.z;
if ((idx & 3) == 3) some_value = values.w;
```
This commit is contained in:
ReinUsesLisp 2019-05-23 20:27:54 -03:00
parent 46177901b8
commit d8827b07b5
1 changed files with 20 additions and 3 deletions
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23
src/video_core/renderer_opengl/gl_shader_decompiler.cpp
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@ -577,9 +577,26 @@ private:
if (std::holds_alternative<OperationNode>(*offset)) {
// Indirect access
const std::string final_offset = code.GenerateTemporary();
code.AddLine("uint {} = (ftou({}) / 4);", final_offset, Visit(offset));
return fmt::format("{}[{} / 4][{} % 4]", GetConstBuffer(cbuf->GetIndex()),
final_offset, final_offset);
code.AddLine("uint {} = ftou({}) >> 2;", final_offset, Visit(offset));
if (!device.HasComponentIndexingBug()) {
return fmt::format("{}[{} >> 2][{} & 3]", GetConstBuffer(cbuf->GetIndex()),
final_offset, final_offset);
}
// AMD's proprietary GLSL compiler emits ill code for variable component access.
// To bypass this driver bug generate 4 ifs, one per each component.
const std::string pack = code.GenerateTemporary();
code.AddLine("vec4 {} = {}[{} >> 2];", pack, GetConstBuffer(cbuf->GetIndex()),
final_offset);
const std::string result = code.GenerateTemporary();
code.AddLine("float {};", result);
for (u32 swizzle = 0; swizzle < 4; ++swizzle) {
code.AddLine("if (({} & 3) == {}) {} = {}{};", final_offset, swizzle, result,
pack, GetSwizzle(swizzle));
}
return result;
}
UNREACHABLE_MSG("Unmanaged offset node type");