math: new exp and exp2
from https://github.com/ARM-software/optimized-routines,
commit 04884bd04eac4b251da4026900010ea7d8850edc
TOINT_INTRINSICS and EXP_USE_TOINT_NARROW cases are unused.
The underflow exception is signaled if the result is in the subnormal
range even if the result is exact (e.g. exp2(-1023.0)).
code size change: -1672 bytes.
benchmark on x86_64 before, after, speedup:
-Os:
exp rthruput: 12.73 ns/call 6.68 ns/call 1.91x
exp latency: 45.78 ns/call 21.79 ns/call 2.1x
exp2 rthruput: 6.35 ns/call 5.26 ns/call 1.21x
exp2 latency: 26.00 ns/call 16.58 ns/call 1.57x
-O3:
exp rthruput: 12.75 ns/call 6.73 ns/call 1.89x
exp latency: 45.91 ns/call 21.80 ns/call 2.11x
exp2 rthruput: 6.47 ns/call 5.40 ns/call 1.2x
exp2 latency: 26.03 ns/call 16.54 ns/call 1.57x
4 files changed
