Interpreter: Fix fctiwx rounding #9738
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The interpreter implementation of fctiwx was treating rounding mode 0 as "round to nearest, ties towards zero", which is not an actual IEEE-754 rounding mode. The IBM document mentioned in a comment at the top of the function, on the other hand, treats rounding mode 0 as "round to nearest, ties to even", which makes more sense. This fixes one of JMC's console-recorded F-Zero GX replays on JitArm64. (JitArm64 uses an interpreter fallback for fctiwx.)
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Confirmed to sync up the replay on JitArm64 on my phone. Doesn't seem to be a performance loss either. |
lioncash
approved these changes
May 22, 2021
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The interpreter implementation of fctiwx was treating rounding mode 0 as "round to nearest, ties towards zero", which is not an actual IEEE-754 rounding mode. The IBM document mentioned in a comment at the top of the function, on the other hand, treats rounding mode 0 as "round to nearest, ties to even", which makes more sense.
This fixes one of JMC's console-recorded F-Zero GX replays on JitArm64. (JitArm64 uses an interpreter fallback for fctiwx.)