On Fri, May 20, 2011 at 3:12 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> As discussed in the PR, these routines happily look through PHI nodes
> into previous loop iteration. f is initialized in the previous
> loop iteration with f_10 = d_6 == 3; and in the current iteration
> there is f_2 != 0 && d_6 == 4 test. As we look through
> # f_2 = PHI <0(2), f_10(6)> PHI, this is evaluated as
> 0 != 0 && d_6 == 4 (which is correctly false) and
> (d_6 == 3) != 0 && d_6 == 4 (this one is false due to d_6 being
> from one iteration in one case and next one in another case).
> The following patch fixes it, bootstrapped/regtested on x86_64-linux and
> i686-linux, ok for trunk/4.6?
Ok.
Thanks,
Richard.
> 2011-05-20 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/49073
> * gimple-fold.c (and_comparisons_1, or_comparisons_1): Return
> NULL if PHI argument is SSA_NAME, whose def_stmt is dominated
> by the PHI.
> * tree-ssa-ifcombine.c (tree_ssa_ifcombine): Calculate dominators.
>
> * gcc.c-torture/execute/pr49073.c: New test.
>
> --- gcc/gimple-fold.c.jj 2011-05-11 19:39:04.000000000 +0200
> +++ gcc/gimple-fold.c 2011-05-20 11:05:11.000000000 +0200
> @@ -1,5 +1,5 @@
> /* Statement simplification on GIMPLE.
> - Copyright (C) 2010 Free Software Foundation, Inc.
> + Copyright (C) 2010, 2011 Free Software Foundation, Inc.
> Split out from tree-ssa-ccp.c.
>
> This file is part of GCC.
> @@ -2278,8 +2278,19 @@ and_comparisons_1 (enum tree_code code1,
> }
> else if (TREE_CODE (arg) == SSA_NAME)
> {
> - tree temp = and_var_with_comparison (arg, invert,
> - code2, op2a, op2b);
> + tree temp;
> + gimple def_stmt = SSA_NAME_DEF_STMT (arg);
> + /* In simple cases we can look through PHI nodes,
> + but we have to be careful with loops.
> + See PR49073. */
> + if (! dom_info_available_p (CDI_DOMINATORS)
> + || gimple_bb (def_stmt) == gimple_bb (stmt)
> + || dominated_by_p (CDI_DOMINATORS,
> + gimple_bb (def_stmt),
> + gimple_bb (stmt)))
> + return NULL_TREE;
> + temp = and_var_with_comparison (arg, invert, code2,
> + op2a, op2b);
> if (!temp)
> return NULL_TREE;
> else if (!result)
> @@ -2728,8 +2739,19 @@ or_comparisons_1 (enum tree_code code1,
> }
> else if (TREE_CODE (arg) == SSA_NAME)
> {
> - tree temp = or_var_with_comparison (arg, invert,
> - code2, op2a, op2b);
> + tree temp;
> + gimple def_stmt = SSA_NAME_DEF_STMT (arg);
> + /* In simple cases we can look through PHI nodes,
> + but we have to be careful with loops.
> + See PR49073. */
> + if (! dom_info_available_p (CDI_DOMINATORS)
> + || gimple_bb (def_stmt) == gimple_bb (stmt)
> + || dominated_by_p (CDI_DOMINATORS,
> + gimple_bb (def_stmt),
> + gimple_bb (stmt)))
> + return NULL_TREE;
> + temp = or_var_with_comparison (arg, invert, code2,
> + op2a, op2b);
> if (!temp)
> return NULL_TREE;
> else if (!result)
> --- gcc/tree-ssa-ifcombine.c.jj 2011-05-20 08:14:08.000000000 +0200
> +++ gcc/tree-ssa-ifcombine.c 2011-05-20 11:37:24.000000000 +0200
> @@ -1,5 +1,5 @@
> /* Combining of if-expressions on trees.
> - Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
> + Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
> Contributed by Richard Guenther <rguent...@suse.de>
>
> This file is part of GCC.
> @@ -625,6 +625,7 @@ tree_ssa_ifcombine (void)
> int i;
>
> bbs = blocks_in_phiopt_order ();
> + calculate_dominance_info (CDI_DOMINATORS);
>
> for (i = 0; i < n_basic_blocks - NUM_FIXED_BLOCKS; ++i)
> {
> --- gcc/testsuite/gcc.c-torture/execute/pr49073.c.jj 2011-05-20
> 11:38:58.000000000 +0200
> +++ gcc/testsuite/gcc.c-torture/execute/pr49073.c 2011-05-20
> 11:37:40.000000000 +0200
> @@ -0,0 +1,26 @@
> +/* PR tree-optimization/49073 */
> +
> +extern void abort (void);
> +int a[] = { 1, 2, 3, 4, 5, 6, 7 }, c;
> +
> +int
> +main ()
> +{
> + int d = 1, i = 1;
> + _Bool f = 0;
> + do
> + {
> + d = a[i];
> + if (f && d == 4)
> + {
> + ++c;
> + break;
> + }
> + i++;
> + f = (d == 3);
> + }
> + while (d < 7);
> + if (c != 1)
> + abort ();
> + return 0;
> +}
>
> Jakub
>
