s390: Fix --with-arch=... --with-tune=... [PR26877]

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.

2020-03-03  Jakub Jelinek  <jakub@redhat.com>

	PR target/26877
	* config/s390/s390.h (OPTION_DEFAULT_SPECS): Reorder.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 124a06a960a5ca0b52a9e04bbc05dd03b800e2c9..08ce80e25e442efa5ef3b64450b3c3528fccc99e 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,8 @@
 2020-03-03  Jakub Jelinek  <jakub@redhat.com>
 
+       PR target/26877
+       * config/s390/s390.h (OPTION_DEFAULT_SPECS): Reorder.
+
        PR rtl-optimization/94002
        * explow.c (plus_constant): Punt if cst has VOIDmode and
        get_pool_mode is different from mode.

diff --git a/gcc/config/s390/s390.h b/gcc/config/s390/s390.h
index dd3118ee4aff57705a757714ee303154d5889fdd..2e29dbe97e872f2f5c01f6bbe634da4cc6a10462 100644 (file)
--- a/gcc/config/s390/s390.h
+++ b/gcc/config/s390/s390.h
@@ -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);