Commit 5933651a authored by Yukihiro "Matz" Matsumoto's avatar Yukihiro "Matz" Matsumoto

Merge pull request #3157 from cremno/add-mrb_int_mul_overflow

add function for checked mrb_int multiplication
parents 0be4b896 7453a5df
......@@ -62,6 +62,12 @@ mrb_int_sub_overflow(mrb_int minuend, mrb_int subtrahend, mrb_int *difference)
return __builtin_sub_overflow(minuend, subtrahend, difference) || WBCHK(*difference);
}
static inline mrb_bool
mrb_int_mul_overflow(mrb_int multiplier, mrb_int multiplicand, mrb_int *product)
{
return __builtin_mul_overflow(multiplier, multiplicand, product) || WBCHK(*product);
}
#undef WBCHK
#else
......@@ -92,6 +98,35 @@ mrb_int_sub_overflow(mrb_int minuend, mrb_int subtrahend, mrb_int *difference)
return !!(((x ^ z) & (~y ^ z)) & MRB_INT_OVERFLOW_MASK);
}
static inline mrb_bool
mrb_int_mul_overflow(mrb_int multiplier, mrb_int multiplicand, mrb_int *product)
{
#if MRB_INT_BIT == 32
int64_t n = (int64_t)multiplier * multiplicand;
*product = (mrb_int)n;
return !FIXABLE(n);
#else
if (multiplier > 0) {
if (multiplicand > 0) {
if (multiplier > MRB_INT_MAX / multiplicand) return TRUE;
}
else {
if (multiplicand < MRB_INT_MAX / multiplier) return TRUE;
}
}
else {
if (multiplicand > 0) {
if (multiplier < MRB_INT_MAX / multiplicand) return TRUE;
}
else {
if (multiplier != 0 && multiplicand < MRB_INT_MAX / multiplier) return TRUE;
}
}
*product = multiplier * multiplicand;
return FALSE;
#endif
}
#undef MRB_INT_OVERFLOW_MASK
#undef mrb_uint
#undef MRB_UINT_MAKE
......
......@@ -541,10 +541,6 @@ int_to_i(mrb_state *mrb, mrb_value num)
return num;
}
/*tests if N*N would overflow*/
#define SQRT_INT_MAX ((mrb_int)1<<((MRB_INT_BIT-1-MRB_FIXNUM_SHIFT)/2))
#define FIT_SQRT_INT(n) (((n)<SQRT_INT_MAX)&&((n)>=-SQRT_INT_MAX))
mrb_value
mrb_fixnum_mul(mrb_state *mrb, mrb_value x, mrb_value y)
{
......@@ -552,18 +548,14 @@ mrb_fixnum_mul(mrb_state *mrb, mrb_value x, mrb_value y)
a = mrb_fixnum(x);
if (mrb_fixnum_p(y)) {
mrb_float c;
mrb_int b;
mrb_int b, c;
if (a == 0) return x;
b = mrb_fixnum(y);
if (FIT_SQRT_INT(a) && FIT_SQRT_INT(b))
return mrb_fixnum_value(a*b);
c = a * b;
if ((a != 0 && c/a != b) || !FIXABLE(c)) {
return mrb_float_value(mrb, (mrb_float)a*(mrb_float)b);
if (mrb_int_mul_overflow(a, b, &c)) {
return mrb_float_value(mrb, (mrb_float)a * (mrb_float)b);
}
return mrb_fixnum_value((mrb_int)c);
return mrb_fixnum_value(c);
}
return mrb_float_value(mrb, (mrb_float)a * mrb_to_flo(mrb, y));
}
......
......@@ -1862,25 +1862,15 @@ RETRY_TRY_BLOCK:
switch (TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]))) {
case TYPES2(MRB_TT_FIXNUM,MRB_TT_FIXNUM):
{
mrb_value z;
z = mrb_fixnum_mul(mrb, regs[a], regs[a+1]);
mrb_int x, y, z;
switch (mrb_type(z)) {
case MRB_TT_FIXNUM:
{
SET_INT_VALUE(regs[a], mrb_fixnum(z));
}
break;
case MRB_TT_FLOAT:
{
SET_FLOAT_VALUE(mrb, regs[a], mrb_float(z));
}
break;
default:
/* cannot happen */
x = mrb_fixnum(regs[a]);
y = mrb_fixnum(regs[a+1]);
if (mrb_int_mul_overflow(x, y, &z)) {
SET_FLOAT_VALUE(mrb, regs[a], (mrb_float)x * (mrb_float)y);
break;
}
SET_INT_VALUE(regs[a], z);
}
break;
case TYPES2(MRB_TT_FIXNUM,MRB_TT_FLOAT):
......
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