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tree-object-size: Always set computed bit for bdos [PR113012]

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It is always safe to set the computed bit for dynamic object sizes at
the end of collect_object_sizes_for because even in case of a dependency
loop encountered in nested calls, we have an SSA temporary to actually
finish the object size expression.  The reexamine pass for dynamic
object sizes is only for propagation of unknowns and gimplification of
the size expressions, not for loop resolution as in the case of static
object sizes.

gcc/ChangeLog:

	PR tree-optimization/113012
	* tree-object-size.cc (compute_builtin_object_size): Expand
	comment for dynamic object sizes.
	(collect_object_sizes_for): Always set COMPUTED bitmap for
	dynamic object sizes.

gcc/testsuite/ChangeLog:

	PR tree-optimization/113012
	* gcc.dg/ubsan/pr113012.c: New test case.

Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>
This commit is contained in:
Siddhesh Poyarekar 2023-12-18 09:44:00 -05:00
parent fa1158c50a
commit 576c1fc440
2 changed files with 29 additions and 5 deletions
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17
gcc/testsuite/gcc.dg/ubsan/pr113012.c Normal file
View file

@ -0,0 +1,17 @@
/* { dg-do compile } */
/* { dg-options "-fsanitize=undefined" } */
int *
foo (int x, int y, int z, int w)
{
int *p = __builtin_malloc (z * sizeof (int));
int *q = p - 1;
while (--x > 0)
{
if (w + 1 > y)
q = p - 1;
++*q;
++q;
}
return p;
}

17
gcc/tree-object-size.cc
View file

@ -1197,10 +1197,12 @@ compute_builtin_object_size (tree ptr, int object_size_type,
osi.tos = NULL;
}
/* First pass: walk UD chains, compute object sizes that
can be computed. osi.reexamine bitmap at the end will
contain what variables were found in dependency cycles
and therefore need to be reexamined. */
/* First pass: walk UD chains, compute object sizes that can be computed.
osi.reexamine bitmap at the end will contain versions of SSA_NAMES
that need to be reexamined. For both static and dynamic size
computation, reexamination is for propagation across dependency loops.
The dynamic case has the additional use case where the computed
expression needs to be gimplified. */
osi.pass = 0;
osi.changed = false;
collect_object_sizes_for (&osi, ptr);
@ -1835,11 +1837,16 @@ collect_object_sizes_for (struct object_size_info *osi, tree var)
gcc_unreachable ();
}
if (! reexamine || object_sizes_unknown_p (object_size_type, varno))
/* Dynamic sizes use placeholder temps to return an answer, so it is always
safe to set COMPUTED for them. */
if ((object_size_type & OST_DYNAMIC)
|| !reexamine || object_sizes_unknown_p (object_size_type, varno))
{
bitmap_set_bit (computed[object_size_type], varno);
if (!(object_size_type & OST_DYNAMIC))
bitmap_clear_bit (osi->reexamine, varno);
else if (reexamine)
bitmap_set_bit (osi->reexamine, varno);
}
else
{