FRE/PREs redundant store removal code doesn't honor the middle-end
memory model which says that all stores change the dynamic type of
the affected memory region. So it removed the second 'int' store in
MEM[(int *)p_3] = 1;
MEM[(double *)p_3] = 0.0;
MEM[(int *)p_3] = 1;
which is not valid (if not done later DSE removes the first int store
which _is_ valid).
So I am bootstrapping and testing the following fix on
x86_64-unknown-linux-gnu.
Richard.
2016-02-12 Richard Biener <rguent...@suse.de>
PR tree-optimization/69776
* tree-ssa-sccvn.h (vn_reference_lookup): Adjust prototype.
* tree-ssa-sccvn.c (vn_reference_lookup): Add parameter to
indicate whether we can use TBAA to disambiguate against stores.
Use alias-set zero if not.
(visit_reference_op_store): Do not use TBAA when looking up
redundant stores.
* tree-ssa-pre.c (compute_avail): Use TBAA here.
(eliminate_dom_walker::before_dom_children): But not when looking
up redundant stores.
* gcc.dg/torture/pr69776.c: New testcase.
Index: gcc/tree-ssa-sccvn.h
===================================================================
*** gcc/tree-ssa-sccvn.h (revision 233369)
--- gcc/tree-ssa-sccvn.h (working copy)
*************** bool ao_ref_init_from_vn_reference (ao_r
*** 216,222 ****
tree vn_reference_lookup_pieces (tree, alias_set_type, tree,
vec<vn_reference_op_s> ,
vn_reference_t *, vn_lookup_kind);
! tree vn_reference_lookup (tree, tree, vn_lookup_kind, vn_reference_t *);
void vn_reference_lookup_call (gcall *, vn_reference_t *, vn_reference_t);
vn_reference_t vn_reference_insert_pieces (tree, alias_set_type, tree,
vec<vn_reference_op_s> ,
--- 216,222 ----
tree vn_reference_lookup_pieces (tree, alias_set_type, tree,
vec<vn_reference_op_s> ,
vn_reference_t *, vn_lookup_kind);
! tree vn_reference_lookup (tree, tree, vn_lookup_kind, vn_reference_t *, bool);
void vn_reference_lookup_call (gcall *, vn_reference_t *, vn_reference_t);
vn_reference_t vn_reference_insert_pieces (tree, alias_set_type, tree,
vec<vn_reference_op_s> ,
Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c (revision 233369)
--- gcc/tree-ssa-sccvn.c (working copy)
*************** vn_reference_lookup_pieces (tree vuse, a
*** 2230,2240 ****
number if it exists in the hash table. Return NULL_TREE if it does
not exist in the hash table or if the result field of the structure
was NULL.. VNRESULT will be filled in with the vn_reference_t
! stored in the hashtable if one exists. */
tree
vn_reference_lookup (tree op, tree vuse, vn_lookup_kind kind,
! vn_reference_t *vnresult)
{
vec<vn_reference_op_s> operands;
struct vn_reference_s vr1;
--- 2230,2241 ----
number if it exists in the hash table. Return NULL_TREE if it does
not exist in the hash table or if the result field of the structure
was NULL.. VNRESULT will be filled in with the vn_reference_t
! stored in the hashtable if one exists. When TBAA_P is false assume
! we are looking up a store and treat it as having alias-set zero. */
tree
vn_reference_lookup (tree op, tree vuse, vn_lookup_kind kind,
! vn_reference_t *vnresult, bool tbaa_p)
{
vec<vn_reference_op_s> operands;
struct vn_reference_s vr1;
*************** vn_reference_lookup (tree op, tree vuse,
*** 2264,2269 ****
--- 2265,2272 ----
|| !ao_ref_init_from_vn_reference (&r, vr1.set, vr1.type,
vr1.operands))
ao_ref_init (&r, op);
+ if (! tbaa_p)
+ r.ref_alias_set = r.base_alias_set = 0;
vn_walk_kind = kind;
wvnresult =
(vn_reference_t)walk_non_aliased_vuses (&r, vr1.vuse,
*************** visit_reference_op_load (tree lhs, tree
*** 3350,3356 ****
last_vuse = gimple_vuse (stmt);
last_vuse_ptr = &last_vuse;
result = vn_reference_lookup (op, gimple_vuse (stmt),
! default_vn_walk_kind, NULL);
last_vuse_ptr = NULL;
/* We handle type-punning through unions by value-numbering based
--- 3353,3359 ----
last_vuse = gimple_vuse (stmt);
last_vuse_ptr = &last_vuse;
result = vn_reference_lookup (op, gimple_vuse (stmt),
! default_vn_walk_kind, NULL, true);
last_vuse_ptr = NULL;
/* We handle type-punning through unions by value-numbering based
*************** visit_reference_op_store (tree lhs, tree
*** 3472,3478 ****
Otherwise, the vdefs for the store are used when inserting into
the table, since the store generates a new memory state. */
! result = vn_reference_lookup (lhs, vuse, VN_NOWALK, NULL);
if (result)
{
--- 3475,3481 ----
Otherwise, the vdefs for the store are used when inserting into
the table, since the store generates a new memory state. */
! result = vn_reference_lookup (lhs, vuse, VN_NOWALK, NULL, false);
if (result)
{
*************** visit_reference_op_store (tree lhs, tree
*** 3487,3493 ****
&& default_vn_walk_kind == VN_WALK)
{
assign = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, op);
! vn_reference_lookup (assign, vuse, VN_NOWALK, &vnresult);
if (vnresult)
{
VN_INFO (vdef)->use_processed = true;
--- 3490,3496 ----
&& default_vn_walk_kind == VN_WALK)
{
assign = build2 (MODIFY_EXPR, TREE_TYPE (lhs), lhs, op);
! vn_reference_lookup (assign, vuse, VN_NOWALK, &vnresult, false);
if (vnresult)
{
VN_INFO (vdef)->use_processed = true;
Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c (revision 233369)
--- gcc/tree-ssa-pre.c (working copy)
*************** compute_avail (void)
*** 3745,3751 ****
vn_reference_t ref;
vn_reference_lookup (gimple_assign_rhs1 (stmt),
gimple_vuse (stmt),
! VN_WALK, &ref);
if (!ref)
continue;
--- 3745,3751 ----
vn_reference_t ref;
vn_reference_lookup (gimple_assign_rhs1 (stmt),
gimple_vuse (stmt),
! VN_WALK, &ref, true);
if (!ref)
continue;
*************** eliminate_dom_walker::before_dom_childre
*** 4208,4214 ****
tree val;
tree rhs = gimple_assign_rhs1 (stmt);
val = vn_reference_lookup (gimple_assign_lhs (stmt),
! gimple_vuse (stmt), VN_WALK, NULL);
if (TREE_CODE (rhs) == SSA_NAME)
rhs = VN_INFO (rhs)->valnum;
if (val
--- 4208,4214 ----
tree val;
tree rhs = gimple_assign_rhs1 (stmt);
val = vn_reference_lookup (gimple_assign_lhs (stmt),
! gimple_vuse (stmt), VN_WALK, NULL,
false);
if (TREE_CODE (rhs) == SSA_NAME)
rhs = VN_INFO (rhs)->valnum;
if (val
Index: gcc/testsuite/gcc.dg/torture/pr69776.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr69776.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr69776.c (working copy)
***************
*** 0 ****
--- 1,28 ----
+ /* { dg-do run } */
+ /* { dg-additional-options "-fstrict-aliasing" } */
+
+ extern void *malloc (__SIZE_TYPE__);
+ extern void abort (void);
+
+ void __attribute__((noinline,noclone))
+ foo (int *pi)
+ {
+ if (*pi != 1)
+ abort ();
+ }
+
+ int
+ main()
+ {
+ void *p = malloc(sizeof (double));
+ int *pi = p;
+ double *pd = p;
+
+ *pi = 1;
+ int a = *pi;
+ *pd = 0;
+ *pi = a;
+ foo (pi);
+
+ return 0;
+ }
