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re PR tree-optimization/81365 (GCC miscompiles swap)

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PR tree-optimization/81365
	* tree-ssa-phiprop.c (propagate_with_phi): When considering hoisting
	aggregate moves onto bb predecessor edges, make sure there are no
	loads that could alias the lhs in between the start of bb and the
	loads from *phi.

	* g++.dg/torture/pr81365.C: New test.

From-SVN: r250261
This commit is contained in:
Jakub Jelinek 2017-07-17 11:10:23 +02:00 • committed by Jakub Jelinek
parent 764eec6cf5
commit e8dd131313
4 changed files with 76 additions and 1 deletions
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8
gcc/ChangeLog
View file

@ -1,3 +1,11 @@
2017-07-17 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/81365
* tree-ssa-phiprop.c (propagate_with_phi): When considering hoisting
aggregate moves onto bb predecessor edges, make sure there are no
loads that could alias the lhs in between the start of bb and the
loads from *phi.
2017-07-17 Georg-Johann Lay <avr@gjlay.de>
PR 80929

3
gcc/testsuite/ChangeLog
View file

@ -1,5 +1,8 @@
2017-07-17 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/81365
* g++.dg/torture/pr81365.C: New test.
PR tree-optimization/81396
* gcc.dg/tree-ssa/pr81396.c: New test.

39
gcc/testsuite/g++.dg/torture/pr81365.C Normal file
View file

@ -0,0 +1,39 @@
// PR tree-optimization/81365
// { dg-do run }
struct A { unsigned a; };
struct B {
B (const A *x)
{
__builtin_memcpy (b, x, 3 * sizeof (A));
__builtin_memcpy (c, x + 3, sizeof (A));
__builtin_memset (c + 1, 0, sizeof (A));
}
bool
foo (unsigned x)
{
A *it = c;
if (it->a == x || (++it)->a == x)
{
A t(b[0]);
b[0] = *it;
*it = t;
return true;
}
return false;
}
A b[3];
A c[2];
};
int
main ()
{
A x[] = { 4, 8, 12, 18 };
B y(x);
if (!y.foo (18))
__builtin_abort ();
if (!y.foo (4))
__builtin_abort ();
}

27
gcc/tree-ssa-phiprop.c
View file

@ -327,7 +327,7 @@ propagate_with_phi (basic_block bb, gphi *phi, struct phiprop_d *phivn,
if (!dominated_by_p (CDI_POST_DOMINATORS,
bb, gimple_bb (use_stmt)))
continue;
/* Check whether this is a load of *ptr. */
if (!(is_gimple_assign (use_stmt)
&& gimple_assign_rhs_code (use_stmt) == MEM_REF
@ -356,6 +356,9 @@ propagate_with_phi (basic_block bb, gphi *phi, struct phiprop_d *phivn,
insert aggregate copies on the edges instead. */
if (!is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
{
if (!gimple_vdef (use_stmt))
goto next;
/* As we replicate the lhs on each incoming edge all
used SSA names have to be available there. */
if (! for_each_index (gimple_assign_lhs_ptr (use_stmt),
@ -363,6 +366,28 @@ propagate_with_phi (basic_block bb, gphi *phi, struct phiprop_d *phivn,
get_immediate_dominator (CDI_DOMINATORS,
gimple_bb (phi))))
goto next;
gimple *vuse_stmt;
imm_use_iterator vui;
use_operand_p vuse_p;
/* In order to move the aggregate copies earlier, make sure
there are no statements that could read from memory
aliasing the lhs in between the start of bb and use_stmt.
As we require use_stmt to have a VDEF above, loads after
use_stmt will use a different virtual SSA_NAME. */
FOR_EACH_IMM_USE_FAST (vuse_p, vui, vuse)
{
vuse_stmt = USE_STMT (vuse_p);
if (vuse_stmt == use_stmt)
continue;
if (!dominated_by_p (CDI_DOMINATORS,
gimple_bb (vuse_stmt), bb))
continue;
if (ref_maybe_used_by_stmt_p (vuse_stmt,
gimple_assign_lhs (use_stmt)))
goto next;
}
phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
/* Remove old stmt. The phi is taken care of by DCE. */