[Bug gdb/9884] New: Inefficient code in function default_print_registers_info

[Bug gdb/9884] New: Inefficient code in function default_print_registers_info

[richard dot stuckey at arc dot com]

In the function default_print_registers_info in the file infcmd.c, there is the code

      /* If the register name is empty, it is undefined for this
         processor, so don't display anything.  */
      if (gdbarch_register_name (gdbarch, i) == NULL
          || *(gdbarch_register_name (gdbarch, i)) == '\0')
        continue;

      fputs_filtered (gdbarch_register_name (gdbarch, i), file);
      print_spaces_filtered (15 - strlen (gdbarch_register_name
                                          (gdbarch, i)), file);

i.e. the function gdbarch_register_name may be called up to four times for each
register; it would be better to replace this code with


      {
        const char* name = gdbarch_register_name (gdbarch, i);

        /* If the register name is empty, it is undefined for this
           processor, so don't display anything.  */
        if (name == NULL || *name == '\0')
          continue;

        fputs_filtered (name, file);
        print_spaces_filtered (15 - strlen (name), file);
      }

-- 
           Summary: Inefficient code in function
                    default_print_registers_info
           Product: gdb
           Version: 6.8
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: gdb
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: richard dot stuckey at arc dot com
                CC: gdb-prs at sourceware dot org


http://sourceware.org/bugzilla/show_bug.cgi?id=9884

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[Bug gdb/9884] Inefficient code in function default_print_registers_info

[bauermann at sourceware dot org]

------- Additional Comments From bauermann at sourceware dot org  2009-03-08 06:05 -------
I just had a look at the implementation of gdbarch_register_name for some
architectures, and the function is quite efficient, normaly just a few compares
and an array access. Perhaps it's a bit more complex for arches which use a
target description XML, I didn't look much into it. But even then it doesn't
seem to me it would be a problem.

Are you having actual performance issues in GDB because of this? If not, I'd
like to just close this. Not that it would be difficult to apply the code
snippet you mention, but I wouldn't like to start a trend of having bugzillas
opened for cosmetic issues in the source code...

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=9884

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[Bug gdb/9884] Inefficient code in function default_print_registers_info

[bauermann at sourceware dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at sourceware dot|bauermann at sourceware dot
                   |org                         |org
             Status|UNCONFIRMED                 |ASSIGNED


http://sourceware.org/bugzilla/show_bug.cgi?id=9884

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[Bug gdb/9884] Inefficient code in function default_print_registers_info

[richard dot stuckey at arc dot com]

------- Additional Comments From richard dot stuckey at arc dot com  2009-03-09 11:14 -------
No, no performance issue seen, the code just struck me as inelegant: computing
the same quantity four times instead of once.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=9884

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