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tree-optimization/120944 - bogus VN with volatile copies 

The following avoids translating expressions through volatile
copies.

	PR tree-optimization/120944
	* tree-ssa-sccvn.cc (vn_reference_lookup_3): Gate optimizations
	invalid when volatile is involved.

	* gcc.dg/torture/pr120944.c: New testcase.

(cherry picked from commit 6ed1e2ae1a)
This commit is contained in:
Richard Biener 2025-07-04 09:08:19 +02:00
parent eca653215d
commit a35df04c99
2 changed files with 41 additions and 2 deletions
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34
gcc/testsuite/gcc.dg/torture/pr120944.c Normal file
View File

@ -0,0 +1,34 @@
/* { dg-skip-if "" { *-*-* } { "-flto" } { "" } } */
/* { dg-additional-options "-fdump-tree-optimized" } */
#include <stdlib.h>
typedef union {
int u32;
struct
{
int A:1;
int B:2;
int C:3;
};
} u_t;
typedef union {
volatile int u[3];
volatile struct {
u_t a;
int b;
int c;
};
} DATA;
void foo (volatile DATA *d)
{
d->a.u32 = ~0;
u_t u = d->a;
int v = u.A;
if (v)
abort();
}
/* { dg-final { scan-tree-dump-times "if \\\(" 1 "optimized" } } */

9
gcc/tree-ssa-sccvn.cc
View File

@ -2809,7 +2809,8 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
we find a VN result with exactly the same value as the
possible clobber. In this case we can ignore the clobber
and return the found value. */
if (is_gimple_reg_type (TREE_TYPE (lhs))
if (!gimple_has_volatile_ops (def_stmt)
&& is_gimple_reg_type (TREE_TYPE (lhs))
&& types_compatible_p (TREE_TYPE (lhs), vr->type)
&& (ref->ref || data->orig_ref.ref)
&& !data->mask
@ -3093,7 +3094,8 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
else if (is_gimple_reg_type (vr->type)
&& gimple_assign_single_p (def_stmt)
&& gimple_assign_rhs_code (def_stmt) == CONSTRUCTOR
&& CONSTRUCTOR_NELTS (gimple_assign_rhs1 (def_stmt)) == 0)
&& CONSTRUCTOR_NELTS (gimple_assign_rhs1 (def_stmt)) == 0
&& !TREE_THIS_VOLATILE (gimple_assign_lhs (def_stmt)))
{
tree base2;
poly_int64 offset2, size2, maxsize2;
@ -3149,6 +3151,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
&& !reverse_storage_order_for_component_p (vr->operands)
&& !contains_storage_order_barrier_p (vr->operands)
&& gimple_assign_single_p (def_stmt)
&& !TREE_THIS_VOLATILE (gimple_assign_lhs (def_stmt))
&& CHAR_BIT == 8
&& BITS_PER_UNIT == 8
&& BYTES_BIG_ENDIAN == WORDS_BIG_ENDIAN
@ -3307,6 +3310,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
&& !reverse_storage_order_for_component_p (vr->operands)
&& !contains_storage_order_barrier_p (vr->operands)
&& gimple_assign_single_p (def_stmt)
&& !TREE_THIS_VOLATILE (gimple_assign_lhs (def_stmt))
&& TREE_CODE (gimple_assign_rhs1 (def_stmt)) == SSA_NAME)
{
tree lhs = gimple_assign_lhs (def_stmt);
@ -3518,6 +3522,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
the copy kills ref. */
else if (data->vn_walk_kind == VN_WALKREWRITE
&& gimple_assign_single_p (def_stmt)
&& !gimple_has_volatile_ops (def_stmt)
&& (DECL_P (gimple_assign_rhs1 (def_stmt))
|| TREE_CODE (gimple_assign_rhs1 (def_stmt)) == MEM_REF
|| handled_component_p (gimple_assign_rhs1 (def_stmt))))