diff options
Diffstat (limited to 'lib/floatundisf.c')
| -rw-r--r-- | lib/floatundisf.c | 71 |
1 files changed, 37 insertions, 34 deletions
diff --git a/lib/floatundisf.c b/lib/floatundisf.c index 66099e025..79b4b82e3 100644 --- a/lib/floatundisf.c +++ b/lib/floatundisf.c @@ -1,25 +1,27 @@ -//===-- floatundisf.c - Implement __floatundisf ---------------------------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements __floatundisf for the compiler_rt library. -// -//===----------------------------------------------------------------------===// +/*===-- floatundisf.c - Implement __floatundisf ---------------------------=== + * + * The LLVM Compiler Infrastructure + * + * This file is distributed under the University of Illinois Open Source + * License. See LICENSE.TXT for details. + * + * ===----------------------------------------------------------------------=== + * + * This file implements __floatundisf for the compiler_rt library. + * + *===----------------------------------------------------------------------=== + */ #include "int_lib.h" #include <float.h> -// Returns: convert a to a float, rounding toward even. +/* Returns: convert a to a float, rounding toward even. */ -// Assumption: float is a IEEE 32 bit floating point type -// du_int is a 64 bit integral type +/* Assumption: float is a IEEE 32 bit floating point type + * du_int is a 64 bit integral type + */ -// seee eeee emmm mmmm mmmm mmmm mmmm mmmm +/* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */ float __floatundisf(du_int a) @@ -27,17 +29,18 @@ __floatundisf(du_int a) if (a == 0) return 0.0F; const unsigned N = sizeof(du_int) * CHAR_BIT; - int sd = N - __builtin_clzll(a); // number of significant digits - int e = sd - 1; // exponent + int sd = N - __builtin_clzll(a); /* number of significant digits */ + int e = sd - 1; /* 8 exponent */ if (sd > FLT_MANT_DIG) { - // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx - // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR - // 12345678901234567890123456 - // 1 = msb 1 bit - // P = bit FLT_MANT_DIG-1 bits to the right of 1 - // Q = bit FLT_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 FLT_MANT_DIG-1 bits to the right of 1 + * Q = bit FLT_MANT_DIG bits to the right of 1 + * R = "or" of all bits to the right of Q + */ switch (sd) { case FLT_MANT_DIG + 1: @@ -49,25 +52,25 @@ __floatundisf(du_int a) a = (a >> (sd - (FLT_MANT_DIG+2))) | ((a & ((du_int)(-1) >> ((N + FLT_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 FLT_MANT_DIG or FLT_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 FLT_MANT_DIG or FLT_MANT_DIG+1 bits */ if (a & ((du_int)1 << FLT_MANT_DIG)) { a >>= 1; ++e; } - // a is now rounded to FLT_MANT_DIG bits + /* a is now rounded to FLT_MANT_DIG bits */ } else { a <<= (FLT_MANT_DIG - sd); - // a is now rounded to FLT_MANT_DIG bits + /* a is now rounded to FLT_MANT_DIG bits */ } float_bits fb; - fb.u = ((e + 127) << 23) | // exponent - ((su_int)a & 0x007FFFFF); // mantissa + fb.u = ((e + 127) << 23) | /* exponent */ + ((su_int)a & 0x007FFFFF); /* mantissa */ return fb.f; } |