MatCat.OpenSource/8sa1-gcc
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

sra: Fix bug in grp_write propagation (PR 97009)

Browse Source 
SRA represents parts of aggregates which are arrays accessed with
unknown index as "unscalarizable regions."  When there are two such
regions one within another and the outer is only read whereas the
inner is written to, SRA fails to propagate that write information
across assignments.  This means that a second aggregate can contain
data while SRA thinks it does not and the pass can wrongly eliminate
big chunks of assignment from that second aggregate into a third
aggregate, which is what happens in PR 97009.

Fixed by checking all children of unscalariable accesses for the
grp_write flag.

gcc/ChangeLog:

2021-03-31  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/97009
	* tree-sra.c (access_or_its_child_written): New function.
	(propagate_subaccesses_from_rhs): Use it instead of a simple grp_write
	test.

gcc/testsuite/ChangeLog:

2021-03-31  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/97009
	* gcc.dg/tree-ssa/pr97009.c: New test.
This commit is contained in:
Martin Jambor 2021-04-01 10:12:23 +02:00
parent d7cef070bf
commit 19d7167461
2 changed files with 80 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

66
gcc/testsuite/gcc.dg/tree-ssa/pr97009.c Normal file
View File

@ -0,0 +1,66 @@
/* { dg-do run } */
/* { dg-options "-O1" } */
static int __attribute__((noipa))
get_5 (void)
{
return 5;
}
static int __attribute__((noipa))
verify_5 (int v)
{
if (v != 5)
__builtin_abort ();
}
struct T
{
int w;
int a[4];
};
struct S
{
int v;
int x;
struct T t[2];
char alotofstuff[128];
};
volatile int vol;
void __attribute__((noipa))
consume_t (struct T t)
{
vol = t.a[0];
}
int __attribute__((noipa))
foo (int l1, int l2)
{
struct S s1, s2, s3;
int i, j;
s1.v = get_5 ();
for (i = 0; i < l1; i++)
{
for (j = 0; j < l2; j++)
s1.t[i].a[j] = get_5 ();
consume_t(s1.t[i]);
}
s2 = s1;
s3 = s2;
for (i = 0; i < l1; i++)
for (j = 0; j < l2; j++)
verify_5 (s3.t[i].a[j]);
}
int
main (int argc, char *argv[])
{
foo (2, 4);
return 0;
}

15
gcc/tree-sra.c
View File

@ -2723,6 +2723,19 @@ budget_for_propagation_access (tree decl)
return true;
}
/* Return true if ACC or any of its subaccesses has grp_child set. */
static bool
access_or_its_child_written (struct access *acc)
{
if (acc->grp_write)
return true;
for (struct access *sub = acc->first_child; sub; sub = sub->next_sibling)
if (access_or_its_child_written (sub))
return true;
return false;
}
/* Propagate subaccesses and grp_write flags of RACC across an assignment link
to LACC. Enqueue sub-accesses as necessary so that the write flag is
propagated transitively. Return true if anything changed. Additionally, if
@ -2836,7 +2849,7 @@ propagate_subaccesses_from_rhs (struct access *lacc, struct access *racc)
if (rchild->grp_unscalarizable_region
|| !budget_for_propagation_access (lacc->base))
{
if (rchild->grp_write && !lacc->grp_write)
if (!lacc->grp_write && access_or_its_child_written (rchild))
{
ret = true;
subtree_mark_written_and_rhs_enqueue (lacc);