Call GNU ld with -O*

[Marc Glisse <marc dot glisse at inria dot fr>]

Hello,

this patch makes the driver pass -O2 to GNU ld if gcc was called with -O3 
(or more), -Ofast or -Os. Is there a cleaner way to test (optimize > 2 || 
optimize_size) in the driver?

I did a bootstrap on x86_64-unknown-linux-gnu and then manually tested by 
looking at the -v output.

I tried a -O3 bootstrap, but even setting CFLAGS, BOOT_CFLAGS, 
CFLAGS_FOT_TARGET, and the same 3 versions with CXXFLAGS and LDFLAGS, most 
stuff still used the default -O2 -g. And most libraries that are part of 
gcc explicitly use -Wl,-O1 for linking already.

2013-07-12  Marc Glisse  <marc.glisse@inria.fr>

	PR driver/44080
	* gcc.c (LINK_OPT_SPEC): New macro.
	(LINK_COMMAND_SPEC): Use it.

--
Marc Glisse

Index: gcc.c
===================================================================
--- gcc.c	(revision 200921)
+++ gcc.c	(working copy)
@@ -715,36 +715,45 @@ proper position among the other output f
 /* Linker command line options for -fsanitize= late on the command line.  */
 #ifndef SANITIZER_SPEC
 #define SANITIZER_SPEC "\
 %{!nostdlib:%{!nodefaultlibs:%{fsanitize=address:" LIBASAN_SPEC "\
     %{static:%ecannot specify -static with -fsanitize=address}\
     %{fsanitize=thread:%e-fsanitize=address is incompatible with -fsanitize=thread}}\
     %{fsanitize=thread:" LIBTSAN_SPEC "\
     %{!pie:%{!shared:%e-fsanitize=thread linking must be done with -pie or -shared}}}}}"
 #endif
 
+/* GNU ld has -O1 and gold -O2, but we only pass it with -O3, -Os or -Ofast. */
+#ifndef LINK_OPT_SPEC
+#if HAVE_GNU_LD
+#define LINK_OPT_SPEC "%{O*:%{!O0:%{!O1:%{!O2:%{!Og:%{!O:-O2}}}}}} "
+#else
+#define LINK_OPT_SPEC ""
+#endif
+#endif
+
 /* -u* was put back because both BSD and SysV seem to support it.  */
 /* %{static:} simply prevents an error message if the target machine
    doesn't handle -static.  */
 /* We want %{T*} after %{L*} and %D so that it can be used to specify linker
    scripts which exist in user specified directories, or in standard
    directories.  */
 /* We pass any -flto flags on to the linker, which is expected
    to understand them.  In practice, this means it had better be collect2.  */
 /* %{e*} includes -export-dynamic; see comment in common.opt.  */
 #ifndef LINK_COMMAND_SPEC
 #define LINK_COMMAND_SPEC "\
 %{!fsyntax-only:%{!c:%{!M:%{!MM:%{!E:%{!S:\
     %(linker) " \
     LINK_PLUGIN_SPEC \
    "%{flto|flto=*:%<fcompare-debug*} \
-    %{flto} %{flto=*} %l " LINK_PIE_SPEC \
+    %{flto} %{flto=*} %l " LINK_PIE_SPEC LINK_OPT_SPEC \
    "%{fuse-ld=*:-fuse-ld=%*}\
     %X %{o*} %{e*} %{N} %{n} %{r}\
     %{s} %{t} %{u*} %{z} %{Z} %{!nostdlib:%{!nostartfiles:%S}}\
     %{static:} %{L*} %(mfwrap) %(link_libgcc) " SANITIZER_EARLY_SPEC " %o\
     %{fopenmp|ftree-parallelize-loops=*:%:include(libgomp.spec)%(link_gomp)}\
     %{fgnu-tm:%:include(libitm.spec)%(link_itm)}\
     %(mflib) " STACK_SPLIT_SPEC "\
     %{fprofile-arcs|fprofile-generate*|coverage:-lgcov} " SANITIZER_SPEC " \
     %{!nostdlib:%{!nodefaultlibs:%(link_ssp) %(link_gcc_c_sequence)}}\
     %{!nostdlib:%{!nostartfiles:%E}} %{T*} }}}}}}"