Fix SSA_NAME leak due to def_stmt is removed before use_stmt.

-  _5 = __atomic_fetch_or_8 (&set_work_pending_p, 1, 0);
-  # DEBUG old => (long int) _5
+  _6 = .ATOMIC_BIT_TEST_AND_SET (&set_work_pending_p, 0, 1, 0, __atomic_fetch_or_8);
+  # DEBUG old => NULL
   # DEBUG BEGIN_STMT
-  # DEBUG D#2 => _5 & 1
+  # DEBUG D#2 => NULL
...
-  _10 = ~_5;
-  _8 = (_Bool) _10;
-  # DEBUG ret => _8
+  _8 = _6 == 0;
+  # DEBUG ret => (_Bool) _10

confirmed.  convert_atomic_bit_not does this, it checks for single_use
and removes the def, failing to release the name (which would fix this up
IIRC).

Note the function removes stmts in "wrong" order (before uses of LHS
are removed), so it requires larger surgery.  And it leaks SSA names.

gcc/ChangeLog:

	PR target/115872
	* tree-ssa-ccp.cc (convert_atomic_bit_not): Remove use_stmt after use_nop_stmt is removed.
	(optimize_atomic_bit_test_and): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr115872.c: New test.

2 files changed, 24 insertions, 4 deletions

diff --git a/gcc/testsuite/gcc.target/i386/pr115872.c b/gcc/testsuite/gcc.target/i386/pr115872.c
new file mode 100644
index 0000000..9370044
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr115872.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -g" } */
+
+long set_work_pending_p;
+_Bool set_work_pending() {
+  _Bool __trans_tmp_1;
+  long mask = 1, old = __atomic_fetch_or(&set_work_pending_p, mask, 0);
+  __trans_tmp_1 = old & mask;
+  return !__trans_tmp_1;
+}
+void __queue_work() {
+  _Bool ret = set_work_pending();
+  if (ret)
+    __queue_work();
+}
+
diff --git a/gcc/tree-ssa-ccp.cc b/gcc/tree-ssa-ccp.cc
index 3749126..de83d26 100644
--- a/gcc/tree-ssa-ccp.cc
+++ b/gcc/tree-ssa-ccp.cc
@@ -3332,9 +3332,10 @@ convert_atomic_bit_not (enum internal_fn fn, gimple *use_stmt,
     return nullptr;
 
   gimple_stmt_iterator gsi;
-  gsi = gsi_for_stmt (use_stmt);
-  gsi_remove (&gsi, true);
   tree var = make_ssa_name (TREE_TYPE (lhs));
+  /* use_stmt need to be removed after use_nop_stmt,
+     so use_lhs can be released.  */
+  gimple *use_stmt_removal = use_stmt;
   use_stmt = gimple_build_assign (var, BIT_AND_EXPR, lhs, and_mask);
   gsi = gsi_for_stmt (use_not_stmt);
   gsi_insert_before (&gsi, use_stmt, GSI_NEW_STMT);
@@ -3344,6 +3345,8 @@ convert_atomic_bit_not (enum internal_fn fn, gimple *use_stmt,
   gsi_insert_after (&gsi, g, GSI_NEW_STMT);
   gsi = gsi_for_stmt (use_not_stmt);
   gsi_remove (&gsi, true);
+  gsi = gsi_for_stmt (use_stmt_removal);
+  gsi_remove (&gsi, true);
   return use_stmt;
 }
 
@@ -3646,8 +3649,7 @@ optimize_atomic_bit_test_and (gimple_stmt_iterator *gsip,
 		       */
 		    }
 		  var = make_ssa_name (TREE_TYPE (use_rhs));
-		  gsi = gsi_for_stmt (use_stmt);
-		  gsi_remove (&gsi, true);
+		  gimple* use_stmt_removal = use_stmt;
 		  g = gimple_build_assign (var, BIT_AND_EXPR, use_rhs,
 					   and_mask);
 		  gsi = gsi_for_stmt (use_nop_stmt);
@@ -3664,6 +3666,8 @@ optimize_atomic_bit_test_and (gimple_stmt_iterator *gsip,
 		  gsi_insert_after (&gsi, g, GSI_NEW_STMT);
 		  gsi = gsi_for_stmt (use_nop_stmt);
 		  gsi_remove (&gsi, true);
+		  gsi = gsi_for_stmt (use_stmt_removal);
+		  gsi_remove (&gsi, true);
 		}
 	    }
 	  else