diff options
Diffstat (limited to 'lib/floattidf.c')
| -rw-r--r-- | lib/floattidf.c | 75 |
1 files changed, 39 insertions, 36 deletions
diff --git a/lib/floattidf.c b/lib/floattidf.c index 0f72b33f3..b74fa5ec8 100644 --- a/lib/floattidf.c +++ b/lib/floattidf.c @@ -1,27 +1,29 @@ -//===-- floattidf.c - Implement __floattidf -------------------------------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements __floattidf for the compiler_rt library. -// -//===----------------------------------------------------------------------===// +/* ===-- floattidf.c - Implement __floattidf -------------------------------=== + * + * The LLVM Compiler Infrastructure + * + * This file is distributed under the University of Illinois Open Source + * License. See LICENSE.TXT for details. + * + * ===----------------------------------------------------------------------=== + * + * This file implements __floattidf for the compiler_rt library. + * + * ===----------------------------------------------------------------------=== + */ #if __x86_64 #include "int_lib.h" #include <float.h> -// Returns: convert a to a double, rounding toward even. +/* Returns: convert a to a double, rounding toward even.*/ -// Assumption: double is a IEEE 64 bit floating point type -// ti_int is a 128 bit integral type +/* Assumption: double is a IEEE 64 bit floating point type + * ti_int is a 128 bit integral type + */ -// seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm +/* seee eeee eeee mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm */ si_int __clzti2(ti_int a); @@ -33,17 +35,18 @@ __floattidf(ti_int a) const unsigned N = sizeof(ti_int) * CHAR_BIT; const ti_int s = a >> (N-1); a = (a ^ s) - s; - int sd = N - __clzti2(a); // number of significant digits - int e = sd - 1; // exponent + 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 + /* 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: @@ -55,28 +58,28 @@ __floattidf(ti_int a) a = ((tu_int)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 + /* 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 + /* a is now rounded to DBL_MANT_DIG bits */ } else { a <<= (DBL_MANT_DIG - sd); - // a is now rounded to DBL_MANT_DIG bits + /* a is now rounded to DBL_MANT_DIG bits */ } double_bits fb; - fb.u.high = ((su_int)s & 0x80000000) | // sign - ((e + 1023) << 20) | // exponent - ((su_int)(a >> 32) & 0x000FFFFF); // mantissa-high - fb.u.low = (su_int)a; // mantissa-low + fb.u.high = ((su_int)s & 0x80000000) | /* sign */ + ((e + 1023) << 20) | /* exponent */ + ((su_int)(a >> 32) & 0x000FFFFF); /* mantissa-high */ + fb.u.low = (su_int)a; /* mantissa-low */ return fb.f; } |