procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

PR82547: Undetected overflow for UNSIGNED wide_ints

Browse source 
wi::add_large and wi::sub_large weren't setting the overflow bit
correctly for unsigned operations if the result needed fewer HWIs
than the precision.

2017-11-22  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR middle-end/82547
	* wide-int.cc (wi::add_large, wi::sub_large): Fix overflow detection
	for unsigned values with fewer HWIs than the precision.
	(test_overflow): New function.
	(wide_int_cc_tests): Call it.

From-SVN: r255059
This commit is contained in:
Richard Sandiford 2017-11-22 13:58:57 +00:00 • committed by Richard Sandiford
parent a76ef9c5a8
commit 2131f7f5b7
2 changed files with 53 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
gcc/ChangeLog
View file

@ -1,3 +1,11 @@
2017-11-22 Richard Sandiford <richard.sandiford@linaro.org>
PR middle-end/82547
* wide-int.cc (wi::add_large, wi::sub_large): Fix overflow detection
for unsigned values with fewer HWIs than the precision.
(test_overflow): New function.
(wide_int_cc_tests): Call it.
2017-11-22 Richard Sandiford <richard.sandiford@linaro.org>
* emit-rtl.c (init_derived_machine_modes): Make sure ptr_mode

50
gcc/wide-int.cc
View file

@ -1158,7 +1158,7 @@ wi::add_large (HOST_WIDE_INT *val, const HOST_WIDE_INT *op0,
val[len] = mask0 + mask1 + carry;
len++;
if (overflow)
*overflow = false;
*overflow = (sgn == UNSIGNED && carry);
}
else if (overflow)
{
@ -1552,7 +1552,7 @@ wi::sub_large (HOST_WIDE_INT *val, const HOST_WIDE_INT *op0,
val[len] = mask0 - mask1 - borrow;
len++;
if (overflow)
*overflow = false;
*overflow = (sgn == UNSIGNED && borrow);
}
else if (overflow)
{
@ -2345,14 +2345,54 @@ static void run_all_wide_int_tests ()
test_comparisons <VALUE_TYPE> ();
}
/* Test overflow conditions. */
static void
test_overflow ()
{
static int precs[] = { 31, 32, 33, 63, 64, 65, 127, 128 };
static int offsets[] = { 16, 1, 0 };
for (unsigned int i = 0; i < ARRAY_SIZE (precs); ++i)
for (unsigned int j = 0; j < ARRAY_SIZE (offsets); ++j)
{
int prec = precs[i];
int offset = offsets[j];
bool overflow;
wide_int sum, diff;
sum = wi::add (wi::max_value (prec, UNSIGNED) - offset, 1,
UNSIGNED, &overflow);
ASSERT_EQ (sum, -offset);
ASSERT_EQ (overflow, offset == 0);
sum = wi::add (1, wi::max_value (prec, UNSIGNED) - offset,
UNSIGNED, &overflow);
ASSERT_EQ (sum, -offset);
ASSERT_EQ (overflow, offset == 0);
diff = wi::sub (wi::max_value (prec, UNSIGNED) - offset,
wi::max_value (prec, UNSIGNED),
UNSIGNED, &overflow);
ASSERT_EQ (diff, -offset);
ASSERT_EQ (overflow, offset != 0);
diff = wi::sub (wi::max_value (prec, UNSIGNED) - offset,
wi::max_value (prec, UNSIGNED) - 1,
UNSIGNED, &overflow);
ASSERT_EQ (diff, 1 - offset);
ASSERT_EQ (overflow, offset > 1);
}
}
/* Run all of the selftests within this file, for all value types. */
void
wide_int_cc_tests ()
{
run_all_wide_int_tests <wide_int> ();
run_all_wide_int_tests <offset_int> ();
run_all_wide_int_tests <widest_int> ();
run_all_wide_int_tests <wide_int> ();
run_all_wide_int_tests <offset_int> ();
run_all_wide_int_tests <widest_int> ();
test_overflow ();
}
} // namespace selftest