Hi!
As documented in tree.h for TREE_THIS_VOLATILE:
If this bit is set in an expression, so is TREE_SIDE_EFFECTS.
so copying just TREE_THIS_VOLATILE is not sufficient.
On 4.6 branch this resulted in ICEs in gimple_rhs_has_side_effects.
Bootstrapped/regtested on x86_64-linux and i686-linux, committed after
IRC discussion with richi.
2011-12-08 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/51466
* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Also copy
TREE_SIDE_EFFECTS.
* gcc.c-torture/execute/pr51466.c: New test.
--- gcc/tree-ssa-forwprop.c.jj 2011-11-29 08:58:52.000000000 +0100
+++ gcc/tree-ssa-forwprop.c 2011-12-08 15:17:01.474873355 +0100
@@ -929,10 +929,12 @@ forward_propagate_addr_expr_1 (tree name
*def_rhs_basep = build2 (MEM_REF, TREE_TYPE (*def_rhs_basep),
new_base, new_offset);
TREE_THIS_VOLATILE (*def_rhs_basep) = TREE_THIS_VOLATILE (lhs);
+ TREE_SIDE_EFFECTS (*def_rhs_basep) = TREE_SIDE_EFFECTS (lhs);
TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (lhs);
new_lhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
gimple_assign_set_lhs (use_stmt, new_lhs);
TREE_THIS_VOLATILE (new_lhs) = TREE_THIS_VOLATILE (lhs);
+ TREE_SIDE_EFFECTS (new_lhs) = TREE_SIDE_EFFECTS (lhs);
*def_rhs_basep = saved;
tidy_after_forward_propagate_addr (use_stmt);
/* Continue propagating into the RHS if this was not the
@@ -1011,10 +1013,12 @@ forward_propagate_addr_expr_1 (tree name
*def_rhs_basep = build2 (MEM_REF, TREE_TYPE (*def_rhs_basep),
new_base, new_offset);
TREE_THIS_VOLATILE (*def_rhs_basep) = TREE_THIS_VOLATILE (rhs);
+ TREE_SIDE_EFFECTS (*def_rhs_basep) = TREE_SIDE_EFFECTS (rhs);
TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (rhs);
new_rhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
gimple_assign_set_rhs1 (use_stmt, new_rhs);
TREE_THIS_VOLATILE (new_rhs) = TREE_THIS_VOLATILE (rhs);
+ TREE_SIDE_EFFECTS (new_rhs) = TREE_SIDE_EFFECTS (rhs);
*def_rhs_basep = saved;
fold_stmt_inplace (use_stmt_gsi);
tidy_after_forward_propagate_addr (use_stmt);
--- gcc/testsuite/gcc.c-torture/execute/pr51466.c.jj 2011-12-08
15:25:42.084966108 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr51466.c 2011-12-08
15:25:18.000000000 +0100
@@ -0,0 +1,43 @@
+/* PR tree-optimization/51466 */
+
+extern void abort (void);
+
+__attribute__((noinline, noclone)) int
+foo (int i)
+{
+ volatile int v[4];
+ int *p;
+ v[i] = 6;
+ p = (int *) &v[i];
+ return *p;
+}
+
+__attribute__((noinline, noclone)) int
+bar (int i)
+{
+ volatile int v[4];
+ int *p;
+ v[i] = 6;
+ p = (int *) &v[i];
+ *p = 8;
+ return v[i];
+}
+
+__attribute__((noinline, noclone)) int
+baz (int i)
+{
+ volatile int v[4];
+ int *p;
+ v[i] = 6;
+ p = (int *) &v[0];
+ *p = 8;
+ return v[i];
+}
+
+int
+main ()
+{
+ if (foo (3) != 6 || bar (2) != 8 || baz (0) != 8 || baz (1) != 6)
+ abort ();
+ return 0;
+}
Jakub
