musl/src/math/pow.c, branch master

math: new pow

2019年04月18日T03:45:40+00:00

from https://github.com/ARM-software/optimized-routines,
commit 04884bd04eac4b251da4026900010ea7d8850edc
The underflow exception is signaled if the result is in the subnormal
range even if the result is exact.
code size change: +3421 bytes.
benchmark on x86_64 before, after, speedup:
-Os:
 pow rthruput: 102.96 ns/call 33.38 ns/call 3.08x
 pow latency: 144.37 ns/call 54.75 ns/call 2.64x
-O3:
 pow rthruput: 98.91 ns/call 32.79 ns/call 3.02x
 pow latency: 138.74 ns/call 53.78 ns/call 2.58x

math: fix pow signed shift ub

2016年10月20日T05:32:27+00:00

j is int32_t and thus j<<31 is undefined if j==1, so j is changed to
uint32_t locally as a quick fix, the generated code is not affected.
(this is a strict conformance fix, future c standard may allow 1<<31,
see DR 463. the bug was inherited from freebsd fdlibm, the proper fix
is to use uint32_t for all bit hacks, but that requires more intrusive
changes.)
reported by Daniel Sabogal

math: fix pow(+-0,-inf) not to raise divbyzero flag

2015年04月18日T04:18:52+00:00

this reverts the commit f29fea00b5bc72d4b8abccba2bb1e312684d1fce
which was based on a bug in C99 and POSIX and did not match IEEE-754
http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1515.pdf

math: fix pow(x,-1) to raise underflow properly

2013年08月15日T15:13:24+00:00

if FLT_EVAL_METHOD!=0 check if (double)(1/x) is subnormal and not a
power of 2 (if 1/x is power of 2 then either it is exact or the
long double to double rounding already raised inexact and underflow)

math: fix pow(0,-inf) to raise divbyzero flag

2013年08月15日T10:08:45+00:00

clean up pow.c and powf.c

2012年03月20日T19:04:53+00:00

fix comments about special cases

code cleanup of named constants

2012年03月19日T22:41:19+00:00

zero, one, two, half are replaced by const literals
The policy was to use the f suffix for float consts (1.0f),
but don't use suffix for long double consts (these consts
can be exactly represented as double).

math cleanup: use 1.0f instead of 1.0F

2012年03月13日T20:11:46+00:00

first commit of the new libm!

2012年03月13日T05:17:53+00:00

thanks to the hard work of Szabolcs Nagy (nsz), identifying the best
(from correctness and license standpoint) implementations from freebsd
and openbsd and cleaning them up! musl should now fully support c99
float and long double math functions, and has near-complete complex
math support. tgmath should also work (fully on gcc-compatible
compilers, and mostly on any c99 compiler).
based largely on commit 0376d44a890fea261506f1fc63833e7a686dca19 from
nsz's libm git repo, with some additions (dummy versions of a few
missing long double complex functions, etc.) by me.
various cleanups still need to be made, including re-adding (if
they're correct) some asm functions that were dropped.