diff options
author | Pascal Stumpf <pascal@cvs.openbsd.org> | 2016-09-05 11:36:24 +0000 |
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committer | Pascal Stumpf <pascal@cvs.openbsd.org> | 2016-09-05 11:36:24 +0000 |
commit | 655378bb3dd91f8a437ea1ae76418d3bc7a9ce81 (patch) | |
tree | dd8fc208f2e4ad444932d160a27907580cc022bf /lib/libcompiler_rt/floatuntidf.c | |
parent | afa2339506d84c1497f41a4b29b6624257b7253b (diff) |
Import libcompiler_rt 3.9.0, LLVM's replacement for libgcc.
This is the lib/builtin directory of the compiler-rt source tarball.
comments/ok patrick@, ok kettenis@
Diffstat (limited to 'lib/libcompiler_rt/floatuntidf.c')
-rw-r--r-- | lib/libcompiler_rt/floatuntidf.c | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/lib/libcompiler_rt/floatuntidf.c b/lib/libcompiler_rt/floatuntidf.c new file mode 100644 index 00000000000..960265d8077 --- /dev/null +++ b/lib/libcompiler_rt/floatuntidf.c @@ -0,0 +1,80 @@ +/* ===-- floatuntidf.c - Implement __floatuntidf ---------------------------=== + * + * The LLVM Compiler Infrastructure + * + * This file is dual licensed under the MIT and the University of Illinois Open + * Source Licenses. See LICENSE.TXT for details. + * + * ===----------------------------------------------------------------------=== + * + * This file implements __floatuntidf for the compiler_rt library. + * + * ===----------------------------------------------------------------------=== + */ + +#include "int_lib.h" + +#ifdef CRT_HAS_128BIT + +/* Returns: convert a to a double, rounding toward even. */ + +/* Assumption: double is a IEEE 64 bit floating point type + * tu_int is a 128 bit integral type + */ + +/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */ + +COMPILER_RT_ABI double +__floatuntidf(tu_int a) +{ + if (a == 0) + return 0.0; + const unsigned N = sizeof(tu_int) * CHAR_BIT; + int sd = N - __clzti2(a); /* number of significant digits */ + int e = sd - 1; /* exponent */ + if (sd > DBL_MANT_DIG) + { + /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx + * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR + * 12345678901234567890123456 + * 1 = msb 1 bit + * P = bit DBL_MANT_DIG-1 bits to the right of 1 + * Q = bit DBL_MANT_DIG bits to the right of 1 + * R = "or" of all bits to the right of Q + */ + switch (sd) + { + case DBL_MANT_DIG + 1: + a <<= 1; + break; + case DBL_MANT_DIG + 2: + break; + default: + a = (a >> (sd - (DBL_MANT_DIG+2))) | + ((a & ((tu_int)(-1) >> ((N + DBL_MANT_DIG+2) - sd))) != 0); + }; + /* finish: */ + a |= (a & 4) != 0; /* Or P into R */ + ++a; /* round - this step may add a significant bit */ + a >>= 2; /* dump Q and R */ + /* a is now rounded to DBL_MANT_DIG or DBL_MANT_DIG+1 bits */ + if (a & ((tu_int)1 << DBL_MANT_DIG)) + { + a >>= 1; + ++e; + } + /* a is now rounded to DBL_MANT_DIG bits */ + } + else + { + a <<= (DBL_MANT_DIG - sd); + /* a is now rounded to DBL_MANT_DIG bits */ + } + double_bits fb; + fb.u.s.high = ((e + 1023) << 20) | /* exponent */ + ((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */ + fb.u.s.low = (su_int)a; /* mantissa-low */ + return fb.f; +} + +#endif /* CRT_HAS_128BIT */ |