Commit Graph

2 Commits

Author SHA1 Message Date
Szabolcs Nagy 393a1cb4ea Move __HAVE_FAST_FMA to math_config.h
Define it consistently with other HAVE_* macros that only affect code
using math_config.h.  This is also closer to the Arm Optimized Routines
code.
2018-07-06 10:29:01 +02:00
Szabolcs Nagy 07e2c32828 New log2 implementation
The new implementation is provided under !__OBSOLETE_MATH, it uses
ISO C99 code.  With default settings the worst case error in nearest
rounding mode is 0.547 ULP with inlined fma and fma contraction.  It uses
a 1 KB lookup table, on aarch64 .text+.rodata size of libm.a is increased
by 1584 bytes.

Note that the math.h header defines log2(x) to be log(x)/Ln2, this is
not changed, so the new code is only used if that macro is suppressed.

Improvements on Cortex-A72:
latency: 2.0x
thruput: 2.2x
2018-06-27 15:40:49 +02:00