gOlogy: skip dbranch at -Og

Delayed slot filling moves insns without any regard to variable
location notes, causing the location information in them to become
incorrect.

Fixing that appears to be quite difficult, but filling delay slots is
hardly an essential optimization to run at -Og, so if the user wants
to privilege debuggability, skip delay slot filling.

for  gcc/ChangeLog

	* opts.c (default_options_table): Do not enable
	OPT_fdelayed_branch at -Og.
	* doc/invoke.texi (-fdelayed-branch): Document it.

From-SVN: r265708

gcc/ChangeLog

+2018-10-31  Alexandre Oliva <aoliva@redhat.com>
+
+	* opts.c (default_options_table): Do not enable
+	OPT_fdelayed_branch at -Og.
+	* doc/invoke.texi (-fdelayed-branch): Document it.
+
 2018-10-31  Richard Henderson  <richard.henderson@linaro.org>
 
 	* optabs-libfuncs.c (build_libfunc_function_visibility):

gcc/doc/invoke.texi

@@ -8595,7 +8595,8 @@ If supported for the target machine, attempt to reorder instructions
 to exploit instruction slots available after delayed branch
 instructions.
 
-Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
+Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os},
+but not at @option{-Og}.
 
 @item -fschedule-insns
 @opindex fschedule-insns

gcc/opts.c

@@ -442,7 +442,7 @@ static const struct default_options default_options_table[] =
     /* -O1 optimizations.  */
     { OPT_LEVELS_1_PLUS, OPT_fdefer_pop, NULL, 1 },
 #if DELAY_SLOTS
-    { OPT_LEVELS_1_PLUS, OPT_fdelayed_branch, NULL, 1 },
+    { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fdelayed_branch, NULL, 1 },
 #endif
     { OPT_LEVELS_1_PLUS, OPT_fguess_branch_probability, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_fcprop_registers, NULL, 1 },