diff options
| -rw-r--r-- | vm_insnhelper.c | 36 |
1 files changed, 29 insertions, 7 deletions
diff --git a/vm_insnhelper.c b/vm_insnhelper.c index ef4c938fc5..04b085571b 100644 --- a/vm_insnhelper.c +++ b/vm_insnhelper.c @@ -3763,17 +3763,39 @@ vm_opt_empty_p(VALUE recv) } static VALUE +fix_succ(VALUE x) +{ + switch (x) { + case ~0UL: + /* 0xFFFF_FFFF == INT2FIX(-1) + * `-1.succ` is of course 0. */ + return INT2FIX(0); + case RSHIFT(~0UL, 1): + /* 0x7FFF_FFFF == LONG2FIX(0x3FFF_FFFF) + * 0x3FFF_FFFF + 1 == 0x4000_0000, which is a Bignum. */ + return rb_uint2big(1UL << (SIZEOF_LONG * CHAR_BIT - 2)); + default: + /* 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 + * + * Here, if we put y := INT2FIX(1): + * + * == x + INT2FIX(1) - 1 + * == x + 2 . + */ + return x + 2; + } +} + +static VALUE vm_opt_succ(VALUE recv) { if (FIXNUM_P(recv) && BASIC_OP_UNREDEFINED_P(BOP_SUCC, INTEGER_REDEFINED_OP_FLAG)) { - /* fixnum + INT2FIX(1) */ - if (recv == LONG2FIX(FIXNUM_MAX)) { - return LONG2NUM(FIXNUM_MAX + 1); - } - else { - return recv - 1 + INT2FIX(1); - } + return fix_succ(recv); } else if (SPECIAL_CONST_P(recv)) { return Qundef; |