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middle-end/113396 - int128 array index and value-ranges 

The following fixes bogus truncation of a value-range for an int128
array index when computing the maximum extent for a variable array
reference.  Instead of possibly slowing things down by using
widest_int the following makes sure the range bounds fit within
the constraints offset_int were designed for.

	PR middle-end/113396
	* tree-dfa.cc (get_ref_base_and_extent): Use index range
	bounds only if they fit within the address-range constraints
	of offset_int.

	* gcc.dg/torture/pr113396.c: New testcase.
pull/46/merge
Richard Biener 2024-03-19 15:25:16 +01:00
parent 994d8f922b
commit 6a55e39bdb
2 changed files with 23 additions and 2 deletions
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19
gcc/testsuite/gcc.dg/torture/pr113396.c Normal file
View File

@ -0,0 +1,19 @@
/* { dg-do run } */
/* { dg-require-effective-target int128 } */
unsigned char m[] = {5, 79, 79, 79, 79};
__int128 p;
int main()
{
int g1 = 0;
p = 0;
for (int aj = 0; aj < 256; aj++)
{
m[0] = -4;
for (; p >= 0; p -= 1) {
g1 = m[p];
}
}
if (g1 != 0xfc)
__builtin_abort();
}

6
gcc/tree-dfa.cc
View File

@ -549,7 +549,8 @@ get_ref_base_and_extent (tree exp, poly_int64 *poffset,
/* Try to constrain maxsize with range information. */
offset_int omax
= offset_int::from (max, TYPE_SIGN (TREE_TYPE (index)));
if (known_lt (lbound, omax))
if (wi::get_precision (max) <= ADDR_MAX_BITSIZE
&& known_lt (lbound, omax))
{
poly_offset_int rmaxsize;
rmaxsize = (omax - lbound + 1)
@ -567,7 +568,8 @@ get_ref_base_and_extent (tree exp, poly_int64 *poffset,
/* Try to adjust bit_offset with range information. */
offset_int omin
= offset_int::from (min, TYPE_SIGN (TREE_TYPE (index)));
if (known_le (lbound, omin))
if (wi::get_precision (min) <= ADDR_MAX_BITSIZE
&& known_le (lbound, omin))
{
poly_offset_int woffset
= wi::sext (omin - lbound,