SPU LLVM: Improve approximate FCEQ/FCMEQ #8729
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any update? |
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Fixes bottom-right quarter of godrays in TLoU |
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Kick this to master branch please... |
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Pending a change + rebase that Whatcookie will push |
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Rebased and added a simple optimization for comparisons against safe constants. |
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| if (safe_float_compare.any()) |
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Int comparison is preferred over float.
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There may be extra latency when switching between floating point and integer execution domains. It may be faster regardless on intel where floating comparisons are 4 cycle latency and int comparisons are 1 cycle, but on zen they're both 1 cycle so I think it's ideal to use the float comparison first since future intel cpus may also have fast floating comparisons like zen.
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Should be fine either way, it barely matters in practice.
- It's 100% accurate, but will sit under approx xfloat anyways - Attempts to use a single instruction when 1 value is constant
Accurately emulate SPU floating compare equals by using integer comparisons when the floating value will be interpreted as NAN by x86 hardware.