[Bug target/59587] New: cpu_names in i386.c is accessed with wrong index

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59587

            Bug ID: 59587
           Summary: cpu_names in i386.c is accessed with wrong index
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: ubizjak at gmail dot com

i386.c has

static const char *const cpu_names[TARGET_CPU_DEFAULT_max] =
{
  "generic",
...
  "btver2"
};
...
      if (!opts->x_ix86_tune_string)
        {
          opts->x_ix86_tune_string = cpu_names[TARGET_CPU_DEFAULT];
          ix86_tune_defaulted = 1;
        }
...
  fprintf (file, "%*sarch = %d (%s)\n",
           indent, "",
           ptr->arch,
           ((ptr->arch < TARGET_CPU_DEFAULT_max)
            ? cpu_names[ptr->arch]
            : "<unknown>"));

  fprintf (file, "%*stune = %d (%s)\n",
           indent, "",
           ptr->tune,
           ((ptr->tune < TARGET_CPU_DEFAULT_max)
            ? cpu_names[ptr->tune]
            : "<unknown>"));

But ptr->arch and ptr->tune are set by

  ptr->arch = ix86_arch;
  ptr->schedule = ix86_schedule;
  ptr->tune = ix86_tune;

ix86_arch is set by

/* Which instruction set architecture to use.  */
enum processor_type ix86_arch;

ix86_arch = processor_alias_table[i].processor;

and ix86_tune is set by

/* Which cpu are we optimizing for.  */
enum processor_type ix86_tune;

ix86_tune = processor_alias_table[i].processor;

We are using enum processor_type as index to access array of
enum target_cpu_default

enum target_cpu_default
{
  TARGET_CPU_DEFAULT_generic = 0, 
...
  TARGET_CPU_DEFAULT_max
};

x86 backend only uses TARGET_CPU_DEFAULT_generic to set up the
default tuning:

#ifndef TARGET_CPU_DEFAULT
#define TARGET_CPU_DEFAULT TARGET_CPU_DEFAULT_generic
#endif
...
      if (!opts->x_ix86_tune_string)
        {
          opts->x_ix86_tune_string = cpu_names[TARGET_CPU_DEFAULT];
          ix86_tune_defaulted = 1;
        }

We never define a different TARGET_CPU_DEFAULT.  When GCC is
configured with --with-arch=/--with-cpu=, we have

[hjl@gnu-6 build-x86_64-linux]$ cat gcc/configargs.h 
/* Generated automatically. */
static const char configuration_arguments[] =
"/export/gnu/import/git/gcc/configure --enable-languages=c,c++,fortran
--disable-bootstrap --prefix=/usr/gcc-4.9.0 --with-local-prefix=/usr/local
--enable-gnu-indirect-function --with-fpmath=sse";
static const char thread_model[] = "posix";

static const struct {
  const char *name, *value;
} configure_default_options[] = { { "cpu", "generic" }, { "arch", "x86-64" } };
[hjl@gnu-6 build-x86_64-linux]$ 

which passes -march=/-mtune= to toplev.c.