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forwprop: Improve rejection of overlapping for copyprop of aggregates [PR121841] 

Here we have:
tmp = src1[0];
dest1[0] = tmp;
where src1 and dest1 are decls.
We currently reject this as the bases are different but since the bases
are decls we know they won't overlap.
This adds the extra check to allow this.

Bootstrapped and tested on x86_64-linux-gnu.

	PR tree-optimization/121841

gcc/ChangeLog:

	* tree-ssa-forwprop.cc (optimize_agr_copyprop_1): Allow
	two different decls as bases as non-overlapping bases.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/copy-prop-aggregate-struct-1.c: New test.

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>
This commit is contained in:
Andrew Pinski 2025-09-07 09:33:07 -07:00
parent 1b9c218d14
commit 7e1143abd3
2 changed files with 30 additions and 3 deletions
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21
gcc/testsuite/gcc.dg/tree-ssa/copy-prop-aggregate-struct-1.c Normal file
View File

@ -0,0 +1,21 @@
/* { dg-do compile } */
/* { dg-options "-O1 -fdump-tree-forwprop1-details -fdump-tree-optimized" } */
/* PR tree-optimization/121841 */
struct U2 {
int i[1024];
};
struct U2 g_284[1] = {{0UL}};
struct U2 g_283[1];
/* g_284[0] and g_283[0] are known not to
overlap so a copy prop can happen. */
void func_1() {
struct U2 removeme;
removeme = g_284[0];
g_283[0] = removeme;
}
/* { dg-final { scan-tree-dump-times "after previous" 1 "forwprop1" } } */
/* { dg-final { scan-tree-dump-not "removeme " "optimized" } } */

12
gcc/tree-ssa-forwprop.cc
View File

@ -1467,11 +1467,17 @@ optimize_agr_copyprop_1 (gimple *stmt, gimple *use_stmt,
tree base1 = get_addr_base_and_unit_offset (dest2, &offset1);
tree base2 = get_addr_base_and_unit_offset (src, &offset2);
poly_int64 size = tree_to_poly_int64 (len);
/* If the bases are 2 different decls,
then there can be no overlapping. */
if (base1 && base2
&& DECL_P (base1) && DECL_P (base2)
&& base1 != base2)
;
/* If we can't figure out the base or the bases are
not equal then fall back to an alignment check. */
if (!base1
|| !base2
|| !operand_equal_p (base1, base2))
else if (!base1
|| !base2
|| !operand_equal_p (base1, base2))
{
unsigned int align1 = get_object_alignment (src);
unsigned int align2 = get_object_alignment (dest2);