Re: [PATCH, RFC] Add support for choosing disassembler cpu in GDB for POWER.

[Peter Bergner <bergner@vnet.ibm.com>]

On 10/28/16 9:15 AM, Ulrich Weigand wrote:
> It's probably not that important to exactly match objdump
> behavior here.  B.t.w. how do you even enter a space as
> separator with the -M option?

bergner@genoa:~$ objdump -d -M'power5 power6' wait.o  | grep warning
warning: ignoring unknown -Mpower5 power6 option



> I thought rather that it would be preferable to refactor the
> objdump code first, so that even in objdump, there is already
> a generic printing routine that simply works on a list of
> option name / description pairs provided by the target back-end.
> 
> Then we could simply make that list of option name / description
> pairs available to GDB and use it in a GDB generic print routine
> that then automatically looks similar to the native objdump
> help output.

But not all arches have descriptions paired with the option name.
Looking at Pedro's objdump output from before:

The following ARM specific disassembler options are supported for use with
the -M switch:
  reg-names-special-atpcs  Select special register names used in the ATPCS
  reg-names-atpcs          Select register names used in the ATPCS
  reg-names-apcs           Select register names used in the APCS
  reg-names-std            Select register names used in ARM's ISA documentation
  reg-names-gcc            Select register names used by GCC
  reg-names-raw            Select raw register names
  force-thumb              Assume all insns are Thumb insns
  no-force-thumb           Examine preceding label to determine an insn's type

This would work well for what you propose, but on power, we just dump them out:

The following PPC specific disassembler options are supported for use with
the -M switch:
 403, 405, 440, 464, 476, 601, 603, 604, 620, 7400, 7410, 7450, 7455,
 750cl, 821, 850, 860, a2, altivec, any, booke, booke32, cell, com,
 e200z4, e300, e500, e500mc, e500mc64, e5500, e6500, e500x2, efs, power4,
 power5, power6, power7, power8, power9, ppc, ppc32, ppc64, ppc64bridge,
 ppcps, pwr, pwr2, pwr4, pwr5, pwr5x, pwr6, pwr7, pwr8, pwr9, pwrx,
 spe, titan, vle, vsx, htm, 32, 64

I wouldn't want all of those cpus dumped out on one line apiece ala:

The following PPC specific disassembler options are supported for use with
the -M switch:
   403
   405
   440
   464
   476
   601
   ...

That would get very long!


Peter