tarantool / luajit / 30575571118

93%

push

github

ARM: Make hard-float tobit conversions match JIT backend behavior.

Reported by Peter Cawley.

(cherry picked from commit 32a683d22)

On the ARM architecture, the `tobit()` function incorrectly truncates
instead of rounding to the nearest integer. This leads to inconsistency
between various VMs (comparing to x86/x64, for example) and between the
ARM VM and JIT.

This patch uses an addition of 2^52 + 2^51 constant to the given
argument to convert it to the nearest integer value. After reading the
lowest 32 bits of the register, we get the expected result.

The test is the same as for the previous commit.

Sergey Kaplun:
* added the description for the problem

Part of tarantool/tarantool#12880

Reviewed-by: Evgeniy Temirgaleev <e.temirgaleev@tarantool.org>
Reviewed-by: Sergey Bronnikov <sergeyb@tarantool.org>
Signed-off-by: Sergey Kaplun <skaplun@tarantool.org>

5742 of 6061 branches covered (94.74%)

Branch coverage included in aggregate %.

21913 of 23560 relevant lines covered (93.01%)

3970954.55 hits per line