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#ifndef INTERNAL_FIXNUM_H /* -*- C -*- */
#define INTERNAL_FIXNUM_H
/**
* @file
* @brief Internal header for Fixnums.
* @author \@shyouhei
* @copyright This file is a part of the programming language Ruby.
* Permission is hereby granted, to either redistribute and/or
* modify this file, provided that the conditions mentioned in the
* file COPYING are met. Consult the file for details.
*/
#if HAVE_LONG_LONG && SIZEOF_LONG * 2 <= SIZEOF_LONG_LONG
# define DLONG LONG_LONG
# define DL2NUM(x) LL2NUM(x)
#elif defined(HAVE_INT128_T)
# define DLONG int128_t
# define DL2NUM(x) (RB_FIXABLE(x) ? LONG2FIX(x) : rb_int128t2big(x))
VALUE rb_int128t2big(int128_t n);
#endif
static inline long
rb_overflowed_fix_to_int(long x)
{
return (long)((unsigned long)(x >> 1) ^ (1LU << (SIZEOF_LONG * CHAR_BIT - 1)));
}
static inline VALUE
rb_fix_plus_fix(VALUE x, VALUE y)
{
#ifdef HAVE_BUILTIN___BUILTIN_ADD_OVERFLOW
long lz;
/* NOTE
* (1) `LONG2FIX(FIX2LONG(x)+FIX2LONG(y))`
+ = `((lx*2+1)/2 + (ly*2+1)/2)*2+1`
+ = `lx*2 + ly*2 + 1`
+ = `(lx*2+1) + (ly*2+1) - 1`
+ = `x + y - 1`
* (2) Fixnum's LSB is always 1.
* It means you can always run `x - 1` without overflow.
* (3) Of course `z = x + (y-1)` may overflow.
* At that time true value is
* * positive: 0b0 1xxx...1, and z = 0b1xxx...1
* * nevative: 0b1 0xxx...1, and z = 0b0xxx...1
* To convert this true value to long,
* (a) Use arithmetic shift
* * positive: 0b11xxx...
* * negative: 0b00xxx...
* (b) invert MSB
* * positive: 0b01xxx...
* * negative: 0b10xxx...
*/
if (__builtin_add_overflow((long)x, (long)y-1, &lz)) {
return rb_int2big(rb_overflowed_fix_to_int(lz));
}
else {
return (VALUE)lz;
}
#else
long lz = FIX2LONG(x) + FIX2LONG(y);
return LONG2NUM(lz);
#endif
}
static inline VALUE
rb_fix_minus_fix(VALUE x, VALUE y)
{
#ifdef HAVE_BUILTIN___BUILTIN_SUB_OVERFLOW
long lz;
if (__builtin_sub_overflow((long)x, (long)y-1, &lz)) {
return rb_int2big(rb_overflowed_fix_to_int(lz));
}
else {
return (VALUE)lz;
}
#else
long lz = FIX2LONG(x) - FIX2LONG(y);
return LONG2NUM(lz);
#endif
}
/* arguments must be Fixnum */
static inline VALUE
rb_fix_mul_fix(VALUE x, VALUE y)
{
long lx = FIX2LONG(x);
long ly = FIX2LONG(y);
#ifdef DLONG
return DL2NUM((DLONG)lx * (DLONG)ly);
#else
if (MUL_OVERFLOW_FIXNUM_P(lx, ly)) {
return rb_big_mul(rb_int2big(lx), rb_int2big(ly));
}
else {
return LONG2FIX(lx * ly);
}
#endif
}
/*
* This behaves different from C99 for negative arguments.
* Note that div may overflow fixnum.
*/
static inline void
rb_fix_divmod_fix(VALUE a, VALUE b, VALUE *divp, VALUE *modp)
{
/* assume / and % comply C99.
* ldiv(3) won't be inlined by GCC and clang.
* I expect / and % are compiled as single idiv.
*/
long x = FIX2LONG(a);
long y = FIX2LONG(b);
long div, mod;
if (x == FIXNUM_MIN && y == -1) {
if (divp) *divp = LONG2NUM(-FIXNUM_MIN);
if (modp) *modp = LONG2FIX(0);
return;
}
div = x / y;
mod = x % y;
if (y > 0 ? mod < 0 : mod > 0) {
mod += y;
div -= 1;
}
if (divp) *divp = LONG2FIX(div);
if (modp) *modp = LONG2FIX(mod);
}
/* div() for Ruby
* This behaves different from C99 for negative arguments.
*/
static inline VALUE
rb_fix_div_fix(VALUE x, VALUE y)
{
VALUE div;
rb_fix_divmod_fix(x, y, &div, NULL);
return div;
}
/* mod() for Ruby
* This behaves different from C99 for negative arguments.
*/
static inline VALUE
rb_fix_mod_fix(VALUE x, VALUE y)
{
VALUE mod;
rb_fix_divmod_fix(x, y, NULL, &mod);
return mod;
}
#endif /* INTERNAL_FIXNUM_H */
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