From bd5969fc876a10b18613302db7087ef3c40f18e1 Mon Sep 17 00:00:00 2001 From: Ian Moffett Date: Thu, 7 Mar 2024 17:28:00 -0500 Subject: lib: Add mlibc Signed-off-by: Ian Moffett --- lib/mlibc/options/ansi/musl-generic-math/__expo2.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) create mode 100644 lib/mlibc/options/ansi/musl-generic-math/__expo2.c (limited to 'lib/mlibc/options/ansi/musl-generic-math/__expo2.c') diff --git a/lib/mlibc/options/ansi/musl-generic-math/__expo2.c b/lib/mlibc/options/ansi/musl-generic-math/__expo2.c new file mode 100644 index 0000000..740ac68 --- /dev/null +++ b/lib/mlibc/options/ansi/musl-generic-math/__expo2.c @@ -0,0 +1,16 @@ +#include "libm.h" + +/* k is such that k*ln2 has minimal relative error and x - kln2 > log(DBL_MIN) */ +static const int k = 2043; +static const double kln2 = 0x1.62066151add8bp+10; + +/* exp(x)/2 for x >= log(DBL_MAX), slightly better than 0.5*exp(x/2)*exp(x/2) */ +double __expo2(double x) +{ + double scale; + + /* note that k is odd and scale*scale overflows */ + INSERT_WORDS(scale, (uint32_t)(0x3ff + k/2) << 20, 0); + /* exp(x - k ln2) * 2**(k-1) */ + return exp(x - kln2) * scale * scale; +} -- cgit v1.2.3