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author | Alexey Samsonov <samsonov@google.com> | 2014-02-14 09:20:33 +0000 |
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committer | Alexey Samsonov <samsonov@google.com> | 2014-02-14 09:20:33 +0000 |
commit | 53aa4fda49f94920139300227786ac47c393f1ce (patch) | |
tree | 6d022d04ee279fe1afd89668f346e28a9e3e1559 /lib/builtins/floatuntixf.c | |
parent | 6d999e478fecb10dc43f20b85385d25cc239db0a (diff) |
Move original compiler-rt functions (libgcc replacement) to lib/builtins directory
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@201393 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/builtins/floatuntixf.c')
-rw-r--r-- | lib/builtins/floatuntixf.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/lib/builtins/floatuntixf.c b/lib/builtins/floatuntixf.c new file mode 100644 index 000000000..dbce80f16 --- /dev/null +++ b/lib/builtins/floatuntixf.c @@ -0,0 +1,83 @@ +/* ===-- floatuntixf.c - Implement __floatuntixf ---------------------------=== + * + * 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 __floatuntixf for the compiler_rt library. + * + * ===----------------------------------------------------------------------=== + */ + +#include "int_lib.h" + +#if __x86_64 + +/* Returns: convert a to a long double, rounding toward even. */ + +/* Assumption: long double is a IEEE 80 bit floating point type padded to 128 bits + * tu_int is a 128 bit integral type + */ + +/* gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee | + * 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm + */ + +si_int __clzti2(ti_int a); + +long double +__floatuntixf(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 > LDBL_MANT_DIG) + { + /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx + * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR + * 12345678901234567890123456 + * 1 = msb 1 bit + * P = bit LDBL_MANT_DIG-1 bits to the right of 1 + * Q = bit LDBL_MANT_DIG bits to the right of 1 + * R = "or" of all bits to the right of Q + */ + switch (sd) + { + case LDBL_MANT_DIG + 1: + a <<= 1; + break; + case LDBL_MANT_DIG + 2: + break; + default: + a = (a >> (sd - (LDBL_MANT_DIG+2))) | + ((a & ((tu_int)(-1) >> ((N + LDBL_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 LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits */ + if (a & ((tu_int)1 << LDBL_MANT_DIG)) + { + a >>= 1; + ++e; + } + /* a is now rounded to LDBL_MANT_DIG bits */ + } + else + { + a <<= (LDBL_MANT_DIG - sd); + /* a is now rounded to LDBL_MANT_DIG bits */ + } + long_double_bits fb; + fb.u.high.s.low = (e + 16383); /* exponent */ + fb.u.low.all = (du_int)a; /* mantissa */ + return fb.f; +} + +#endif |