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?
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
