From 30634165980deaeead9f4e71e0ff6a5c9d897776 Mon Sep 17 00:00:00 2001 From: Ian Moffett Date: Mon, 14 Jul 2025 22:39:34 -0400 Subject: usr: libc: Add math.h + musl math impl port Signed-off-by: Ian Moffett --- lib/libc/src/musl-math/__expo2f.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) create mode 100644 lib/libc/src/musl-math/__expo2f.c (limited to 'lib/libc/src/musl-math/__expo2f.c') diff --git a/lib/libc/src/musl-math/__expo2f.c b/lib/libc/src/musl-math/__expo2f.c new file mode 100644 index 0000000..5163e41 --- /dev/null +++ b/lib/libc/src/musl-math/__expo2f.c @@ -0,0 +1,16 @@ +#include "libm.h" + +/* k is such that k*ln2 has minimal relative error and x - kln2 > log(FLT_MIN) */ +static const int k = 235; +static const float kln2 = 0x1.45c778p+7f; + +/* expf(x)/2 for x >= log(FLT_MAX), slightly better than 0.5f*expf(x/2)*expf(x/2) */ +float __expo2f(float x) +{ + float scale; + + /* note that k is odd and scale*scale overflows */ + SET_FLOAT_WORD(scale, (uint32_t)(0x7f + k/2) << 23); + /* exp(x - k ln2) * 2**(k-1) */ + return expf(x - kln2) * scale * scale; +} -- cgit v1.2.3