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Index: gcc/tree-ssa-tail-merge.c
===================================================================
--- a/gcc/tree-ssa-tail-merge.c (revision 185028)
+++ b/gcc/tree-ssa-tail-merge.c (working copy)
@@ -1123,18 +1123,31 @@ gimple_equal_p (same_succ same_succ, gim
}
}
-/* Let GSI skip backwards over local defs. */
+/* Let GSI skip backwards over local defs. Return the earliest vuse in VUSE.
+ Return true in VUSE_ESCAPED if the vuse influenced a SSA_OP_DEF of one of the
+ processed statements. */
static void
-gsi_advance_bw_nondebug_nonlocal (gimple_stmt_iterator *gsi)
+gsi_advance_bw_nondebug_nonlocal (gimple_stmt_iterator *gsi, tree *vuse,
+ bool *vuse_escaped)
{
gimple stmt;
+ tree lvuse;
while (true)
{
if (gsi_end_p (*gsi))
return;
stmt = gsi_stmt (*gsi);
+
+ lvuse = gimple_vuse (stmt);
+ if (lvuse != NULL_TREE)
+ {
+ *vuse = lvuse;
+ if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_DEF))
+ *vuse_escaped = true;
+ }
+
if (!(is_gimple_assign (stmt) && local_def (gimple_get_lhs (stmt))
&& !gimple_has_side_effects (stmt)))
return;
@@ -1150,9 +1163,11 @@ find_duplicate (same_succ same_succ, bas
{
gimple_stmt_iterator gsi1 = gsi_last_nondebug_bb (bb1);
gimple_stmt_iterator gsi2 = gsi_last_nondebug_bb (bb2);
+ tree vuse1 = NULL_TREE, vuse2 = NULL_TREE;
+ bool vuse_escaped = false;
- gsi_advance_bw_nondebug_nonlocal (&gsi1);
- gsi_advance_bw_nondebug_nonlocal (&gsi2);
+ gsi_advance_bw_nondebug_nonlocal (&gsi1, &vuse1, &vuse_escaped);
+ gsi_advance_bw_nondebug_nonlocal (&gsi2, &vuse2, &vuse_escaped);
while (!gsi_end_p (gsi1) && !gsi_end_p (gsi2))
{
@@ -1161,13 +1176,20 @@ find_duplicate (same_succ same_succ, bas
gsi_prev_nondebug (&gsi1);
gsi_prev_nondebug (&gsi2);
- gsi_advance_bw_nondebug_nonlocal (&gsi1);
- gsi_advance_bw_nondebug_nonlocal (&gsi2);
+ gsi_advance_bw_nondebug_nonlocal (&gsi1, &vuse1, &vuse_escaped);
+ gsi_advance_bw_nondebug_nonlocal (&gsi2, &vuse2, &vuse_escaped);
}
if (!(gsi_end_p (gsi1) && gsi_end_p (gsi2)))
return;
+ /* If the incoming vuses are not the same, and the vuse escaped into an
+ SSA_OP_DEF, then merging the 2 blocks will change the value of the def,
+ which potentially means the semantics of one of the blocks will be changed.
+ TODO: make this check more precise. */
+ if (vuse_escaped && vuse1 != vuse2)
+ return;
+
if (dump_file)
fprintf (dump_file, "find_duplicates: <bb %d> duplicate of <bb %d>\n",
bb1->index, bb2->index);
Index: gcc/testsuite/gcc.dg/pr52734.c
===================================================================
--- a/dev/null (new file)
+++ b/gcc/testsuite/gcc.dg/pr52734.c (revision 0)
@@ -0,0 +1,35 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+int bbb = 0;
+
+int __attribute__((noinline,noclone)) aaa(void)
+{
+ ++bbb;
+ return 0;
+}
+
+int __attribute__((noinline,noclone)) ccc(void)
+{
+ int ddd;
+ /* bbb == 0 */
+ if (aaa())
+ return bbb;
+
+ /* bbb == 1 */
+ ddd = bbb;
+ /* bbb == ddd == 1 */
+ if (aaa ())
+ return 0;
+ /* bbb == 2, ddd == 1 */
+
+ return ddd;
+}
+
+int main(void)
+{
+ if (ccc() != 1)
+ __builtin_abort();
+ return 0;
+}
+
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