MIPS: improve -march=native arch detection

If we cannot get info from options and cpuinfo, we try to get from:
  1. getauxval(AT_BASE_PLATFORM), introduced since Linux 5.7
  2. _MIPS_ARCH from host compiler.

mnan=2008 option is also used if __mips_nan2008__ is used.
This can fix the wrong loader usage on r5/r6 platform with
 -march=native.

gcc/ChangeLog:
	* config.gcc: set with_arch to default_mips_arch if no defined.
	* config/mips/driver-native.cc (host_detect_local_cpu):
	  try getauxval(AT_BASE_PLATFORM) and _MIPS_ARCH, too.
	  pass -mnan=2008 if __mips_nan2008__ is defined.
	* config.in: define HAVE_SYS_AUXV_H and HAVE_GETAUXVAL.
	* configure.ac: detect sys/auxv.h and getauxval.
	* configure: regenerated.

1 files changed, 22 insertions, 3 deletions

diff --git a/gcc/config/mips/driver-native.cc b/gcc/config/mips/driver-native.cc
index 47627f8..327ad25 100644
--- a/gcc/config/mips/driver-native.cc
+++ b/gcc/config/mips/driver-native.cc
@@ -23,6 +23,9 @@ along with GCC; see the file COPYING3.  If not see
 #include "system.h"
 #include "coretypes.h"
 #include "tm.h"
+#ifdef HAVE_SYS_AUXV_H
+#include <sys/auxv.h>
+#endif
 
 /* This will be called by the spec parser in gcc.cc when it sees
    a %:local_cpu_detect(args) construct.  Currently it will be called
@@ -41,6 +44,7 @@ const char *
 host_detect_local_cpu (int argc, const char **argv)
 {
   const char *cpu = NULL;
+  char *ret = NULL;
   char buf[128];
   FILE *f;
   bool arch;
@@ -54,7 +58,7 @@ host_detect_local_cpu (int argc, const char **argv)
 
   f = fopen ("/proc/cpuinfo", "r");
   if (f == NULL)
-    return NULL;
+    goto fallback_cpu;
 
   while (fgets (buf, sizeof (buf), f) != NULL)
     if (startswith (buf, "cpu model"))
@@ -84,8 +88,23 @@ host_detect_local_cpu (int argc, const char **argv)
 
   fclose (f);
 
+fallback_cpu:
+#if defined (__mips_nan2008)
+  ret = reconcat (ret, " -mnan=2008 ", NULL);
+#endif
+
+#ifdef HAVE_GETAUXVAL
   if (cpu == NULL)
-    return NULL;
+    cpu = (const char *) getauxval (AT_BASE_PLATFORM);
+#endif
+
+#if defined (_MIPS_ARCH)
+  if (cpu == NULL)
+    cpu = _MIPS_ARCH;
+#endif
+
+  if (cpu)
+    ret = reconcat (ret, ret, "-m", argv[0], "=", cpu, NULL);
 
-  return concat ("-m", argv[0], "=", cpu, NULL);
+  return ret;
 }