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tree-sra: Avoid total SRA if there are incompat. aggregate accesses (PR119085) 

We currently use the types encountered in the function body and not in
type declaration to perform total scalarization.  Bug PR 119085
uncovered that we miss a check that when the same data is accessed
with aggregate types that those are actually compatible.  Without it,
we can base total scalarization on a type that does not "cover" all
live data in a different part of the function.  This patch adds the
check.

gcc/ChangeLog:

2025-07-21  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/119085
	* tree-sra.cc (sort_and_splice_var_accesses): Prevent total
	scalarization if two incompatible aggregates access the same place.

gcc/testsuite/ChangeLog:

2025-07-21  Martin Jambor  <mjambor@suse.cz>

	PR tree-optimization/119085
	* gcc.dg/tree-ssa/pr119085.c: New test.

(cherry picked from commit dabac05714)
This commit is contained in:
Martin Jambor 2025-07-23 11:22:33 +02:00 committed by Martin Jambor
parent 7d3d58554c
commit 2f21edc2a7
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37
gcc/testsuite/gcc.dg/tree-ssa/pr119085.c Normal file
View File

@ -0,0 +1,37 @@
/* { dg-do run } */
/* { dg-options "-O1" } */
struct with_hole {
int x;
long y;
};
struct without_hole {
int x;
int y;
};
union u {
struct with_hole with_hole;
struct without_hole without_hole;
};
void __attribute__((noinline))
test (union u *up, union u u)
{
union u u2;
volatile int f = 0;
u2 = u;
if (f)
u2.with_hole = u.with_hole;
*up = u2;
}
int main(void)
{
union u u;
union u u2;
u2.without_hole.y = -1;
test (&u, u2);
if (u.without_hole.y != -1)
__builtin_abort ();
return 0;
}

6
gcc/tree-sra.cc
View File

@ -2302,6 +2302,12 @@ sort_and_splice_var_accesses (tree var)
}
unscalarizable_region = true;
}
/* If there the same place is accessed with two incompatible
aggregate types, trying to base total scalarization on either of
them can be wrong. */
if (!first_scalar && !types_compatible_p (access->type, ac2->type))
bitmap_set_bit (cannot_scalarize_away_bitmap,
DECL_UID (access->base));
if (grp_same_access_path
&& (!ac2->grp_same_access_path