[Darwin] More specs TLC.

This strips out a few driver specs that are only specifying a default state.
Also warn on an option now ignored, and add some comments to the driver specs
section.

2019-07-19  Iain Sandoe  <iain@sandoe.co.uk>

	* config/darwin.h (DRIVER_SELF_SPECS): Ignore X and Mach specs which
	refer to default conditions.  Warn for the 'y' spec which is ignored
	by current linkers.

From-SVN: r273608

gcc/ChangeLog

+2019-07-19  Iain Sandoe  <iain@sandoe.co.uk>
+
+	* config/darwin.h (DRIVER_SELF_SPECS): Ignore X and Mach specs which
+	refer to default conditions.  Warn for the 'y' spec which is ignored
+	by current linkers.
+
 2019-07-19  Bill Seurer  <seurer@linux.vnet.ibm.com>
 
 	* config/rs6000/rs6000.c (builtin_description, cpu_is_info,

gcc/config/darwin.h

@@ -118,13 +118,23 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 /* True if pragma ms_struct is in effect.  */
 extern GTY(()) int darwin_ms_struct;
 
+/* The majority of Darwin's special driver opts are direct access to ld flags
+   (to save the user typing -Wl,xxxxx or Xlinker xxxxx) but we can't process
+   them here, since doing so will make it appear that there are linker infiles
+   and the linker will invoked even when it is not necessary.
+
+   However, a few can be handled and we can elide options that are silently-
+   ignored defaults, plus warn on obsolete ones that no longer function.  */
 #define DRIVER_SELF_SPECS						\
-  "%{gfull:-g -fno-eliminate-unused-debug-symbols} %<gfull",	\
-  "%{gused:-g -feliminate-unused-debug-symbols} %<gused",	\
-  "%{fapple-kext|mkernel:-static}",				\
-  "%{shared:-Zdynamiclib} %<shared",                            \
-  "%{gsplit-dwarf:%ngsplit-dwarf is not supported on this platform} \
-     %<gsplit-dwarf"
+"%{fapple-kext|mkernel:-static}",					\
+"%{gfull:-g -fno-eliminate-unused-debug-symbols} %<gfull",		\
+"%{gsplit-dwarf:%ngsplit-dwarf is not supported on this platform} \
+   %<gsplit-dwarf",							\
+"%{gused:-g -feliminate-unused-debug-symbols} %<gused",			\
+"%{shared:-Zdynamiclib} %<shared",					\
+"%{static:%{Zdynamic:%e conflicting code gen style switches are used}}",\
+"%{y*:%nthe y option is obsolete and ignored} %<y*",			\
+"%<Mach %<X"
 
 #if LD64_HAS_EXPORT_DYNAMIC
 #define DARWIN_RDYNAMIC "%{rdynamic:-export_dynamic}"
@@ -342,13 +352,11 @@ extern GTY(()) int darwin_ms_struct;
    %{Zunexported_symbols_list*:-unexported_symbols_list %*} \
    %{Zweak_reference_mismatches*:-weak_reference_mismatches %*} \
    %{!Zweak_reference_mismatches*:-weak_reference_mismatches non-weak} \
-   %{X} \
-   %{y*} \
    %{w} \
    %{pagezero_size*} %{segs_read_*} %{seglinkedit} %{noseglinkedit}  \
    %{sectalign*} %{sectobjectsymbols*} %{segcreate*} %{whyload} \
    %{whatsloaded} %{dylinker_install_name*} \
-   %{dylinker} %{Mach} "
+   %{dylinker} "
 
 
 /* Machine dependent libraries.  */