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LibSoftGPU: Remove workaround for i686 depth comparison

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This commit is contained in:
Jelle Raaijmakers 2023-01-09 11:47:30 +01:00
parent 577c552209
commit 44d679ba7e
1 changed files with 0 additions and 29 deletions
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29
Userland/Libraries/LibSoftGPU/Device.cpp
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@ -390,39 +390,10 @@ ALWAYS_INLINE void Device::rasterize(Gfx::IntRect& render_bounds, CB1 set_covera
depth_test_passed = quad.depth >= depth;
break;
case GPU::DepthTestFunction::NotEqual:
#ifdef __SSE__
depth_test_passed = quad.depth != depth;
#else
depth_test_passed = i32x4 {
bit_cast<u32>(quad.depth[0]) != bit_cast<u32>(depth[0]) ? -1 : 0,
bit_cast<u32>(quad.depth[1]) != bit_cast<u32>(depth[1]) ? -1 : 0,
bit_cast<u32>(quad.depth[2]) != bit_cast<u32>(depth[2]) ? -1 : 0,
bit_cast<u32>(quad.depth[3]) != bit_cast<u32>(depth[3]) ? -1 : 0,
};
#endif
break;
case GPU::DepthTestFunction::Equal:
#ifdef __SSE__
depth_test_passed = quad.depth == depth;
#else
//
// This is an interesting quirk that occurs due to us using the x87 FPU when Serenity is
// compiled for the i686 target. When we calculate our depth value to be stored in the buffer,
// it is an 80-bit x87 floating point number, however, when stored into the depth buffer, this is
// truncated to 32 bits. This 38 bit loss of precision means that when x87 `FCOMP` is eventually
// used here the comparison fails.
// This could be solved by using a `long double` for the depth buffer, however this would take
// up significantly more space and is completely overkill for a depth buffer. As such, comparing
// the first 32-bits of this depth value is "good enough" that if we get a hit on it being
// equal, we can pretty much guarantee that it's actually equal.
//
depth_test_passed = i32x4 {
bit_cast<u32>(quad.depth[0]) == bit_cast<u32>(depth[0]) ? -1 : 0,
bit_cast<u32>(quad.depth[1]) == bit_cast<u32>(depth[1]) ? -1 : 0,
bit_cast<u32>(quad.depth[2]) == bit_cast<u32>(depth[2]) ? -1 : 0,
bit_cast<u32>(quad.depth[3]) == bit_cast<u32>(depth[3]) ? -1 : 0,
};
#endif
break;
case GPU::DepthTestFunction::LessOrEqual:
depth_test_passed = quad.depth <= depth;