Re: [PATCH] MIPS: improve -march=native arch detection

[YunQiang Su <yunqiang.su@cipunited.com>]

On Tue, Aug 02, 2022 at 11:10:09AM +0000, YunQiang Su wrote:
> 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.
> 
> This can fix the wrong loader usage on r5/r6 platform with
>  -march=native.
>

ping...

> gcc/ChangeLog:
> 	* config/mips/driver-native.cc (host_detect_local_cpu):
> 	  try getauxval(AT_BASE_PLATFORM) and _MIPS_ARCH, too.
> ---
>  gcc/config/mips/driver-native.cc | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/gcc/config/mips/driver-native.cc b/gcc/config/mips/driver-native.cc
> index 47627f85ce1..9aa7044c0b8 100644
> --- a/gcc/config/mips/driver-native.cc
> +++ b/gcc/config/mips/driver-native.cc
> @@ -19,6 +19,7 @@ along with GCC; see the file COPYING3.  If not see
>  
>  #define IN_TARGET_CODE 1
>  
> +#include <sys/auxv.h>
>  #include "config.h"
>  #include "system.h"
>  #include "coretypes.h"
> @@ -46,15 +47,15 @@ host_detect_local_cpu (int argc, const char **argv)
>    bool arch;
>  
>    if (argc < 1)
> -    return NULL;
> +    goto fallback_cpu;
>  
>    arch = strcmp (argv[0], "arch") == 0;
>    if (!arch && strcmp (argv[0], "tune"))
> -    return NULL;
> +    goto fallback_cpu;
>  
>    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 +85,23 @@ host_detect_local_cpu (int argc, const char **argv)
>  
>    fclose (f);
>  
> +fallback_cpu:
> +/*FIXME: how about other OSes, like FreeBSD? */
> +#ifdef __linux__
> +  /*Note: getauxval may return NULL as:
> +   * AT_BASE_PLATFORM is supported since Linux 5.7
> +   * Or from older version of qemu-user
> +   * */
> +  if (cpu == NULL)
> +    cpu = (const char *) getauxval (AT_BASE_PLATFORM);
> +#endif
> +
>    if (cpu == NULL)
> +#if defined (_MIPS_ARCH)
> +    cpu = _MIPS_ARCH;
> +#else
>      return NULL;
> +#endif
>  
>    return concat ("-m", argv[0], "=", cpu, NULL);
>  }
> -- 
> 2.30.2
>