Hi!
In Fedora we configure GCC with --with-arch=zEC12 --with-tune=z13 right now
and furthermore redhat-rpm-config adds to rpm packages -march=zEC12 -mtune=z13
options (among others). While looking at the git compilation, I've been
surprised that -O2 actually behaves differently from -O2 -mtune=z13 in this
configuration, and indeed, seems --with-tune= is completely ignored on s390
if --with-arch= is specified.
i386 had the same problem, but got that fixed in 2006, see PR26877.
The thing is that for tune, we add -mtune=%(VALUE) only if neither -mtune=
nor -march= is present, but as arch is processed first, it adds
-march=%(VALUE) first and then -march= is always present and so -mtune= is
never added.
By reordering it in OPTION_DEFAULT_SPECS, we process tune first, add the
default -mtune=%(VALUE) if -mtune= or -march= isn't seen, and then
add -march=%(VALUE) if -march= isn't seen. It is true that cc1 etc.
will be then invoked with -mtune=z13 -march=zEC12, but like if the user
specifies it in that order, it should still use z13 tuning and zEC12
ISA set.
Bootstrapped/regtested on s390x-linux, ok for trunk?
2020-02-25 Jakub Jelinek <ja...@redhat.com>
PR target/26877
* config/s390/s390.h (OPTION_DEFAULT_SPECS): Reorder.
--- gcc/config/s390/s390.h.jj 2020-01-12 11:54:36.412413424 +0100
+++ gcc/config/s390/s390.h 2020-02-24 19:04:14.104259482 +0100
@@ -227,11 +227,13 @@ enum processor_flags
#define TARGET_DEFAULT 0
#endif
-/* Support for configure-time defaults. */
+/* Support for configure-time defaults.
+ The order here is important so that -march doesn't squash the
+ tune values. */
#define OPTION_DEFAULT_SPECS \
{ "mode", "%{!mesa:%{!mzarch:-m%(VALUE)}}" }, \
- { "arch", "%{!march=*:-march=%(VALUE)}" }, \
- { "tune", "%{!mtune=*:%{!march=*:-mtune=%(VALUE)}}" }
+ { "tune", "%{!mtune=*:%{!march=*:-mtune=%(VALUE)}}" }, \
+ { "arch", "%{!march=*:-march=%(VALUE)}" }
#ifdef __s390__
extern const char *s390_host_detect_local_cpu (int argc, const char **argv);
Jakub
