gOlogy: do not change code in isolate-paths for warnings only

The isolate-paths pass is activated by various -f flags, but also by
-Wnull-dereference.  Most of its codegen changes are conditioned on at
least one of the -f flags, but those that detect, warn about and
isolate paths that return the address of local variables are enabled
even if the pass is activated only by -Wnull-dereference.

-W flags should not cause codegen changes, so this patch makes the
codegen changes conditional on the presence of any of the -f flags
that activate the pass.  Should we have a separate option to activate
only this kind of transformation?

for  gcc/ChangeLog

	* gimple-ssa-isolate-paths.c
	(find_implicit_erroneous_behavior): Do not change code if the
	pass is running for warnings only.
	(find_explicit_erroneous_behavior): Likewise.

From-SVN: r265473

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f7faf892a9dc9f14080550b6ba502a2d6a562a99..fdfca8ba6bc3768319e1bb2333470caf2e55142d 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-10-24  Alexandre Oliva <aoliva@redhat.com>
+
+       * gimple-ssa-isolate-paths.c
+       (find_implicit_erroneous_behavior): Do not change code if the
+       pass is running for warnings only.
+       (find_explicit_erroneous_behavior): Likewise.
+
 2018-10-24  Michael Meissner  <meissner@linux.ibm.com>
 
        * config/rs6000/rs6000.c (TARGET_MANGLE_DECL_ASSEMBLER_NAME):

diff --git a/gcc/gimple-ssa-isolate-paths.c b/gcc/gimple-ssa-isolate-paths.c
index e1fab61bedabedc078d5fcf034e2c1aaffdcc651..880836c21aa79ac4af38d233cd6b94220b2075c4 100644 (file)
--- a/gcc/gimple-ssa-isolate-paths.c
+++ b/gcc/gimple-ssa-isolate-paths.c
@@ -431,7 +431,9 @@ find_implicit_erroneous_behavior (void)
                                        "declared here");
                          }
 
-                         if (gimple_bb (use_stmt) == bb)
+                         if ((flag_isolate_erroneous_paths_dereference
+                              || flag_isolate_erroneous_paths_attribute)
+                             && gimple_bb (use_stmt) == bb)
                            {
                              duplicate = isolate_path (bb, duplicate, e,
                                                        use_stmt, lhs, true);
@@ -553,9 +555,16 @@ find_explicit_erroneous_behavior (void)
                          inform (DECL_SOURCE_LOCATION(valbase),
                                  "declared here");
                      }
-                     tree zero = build_zero_cst (TREE_TYPE (val));
-                     gimple_return_set_retval (return_stmt, zero);
-                     update_stmt (stmt);
+
+                     /* Do not modify code if the user only asked for
+                        warnings.  */
+                     if (flag_isolate_erroneous_paths_dereference
+                         || flag_isolate_erroneous_paths_attribute)
+                       {
+                         tree zero = build_zero_cst (TREE_TYPE (val));
+                         gimple_return_set_retval (return_stmt, zero);
+                         update_stmt (stmt);
+                       }
                    }
                }
            }