Re: [PATCH] Better checking of ISA/ASE/ABI options for MIPS gas

[Thiemo Seufer <ths@networkno.de>]

Richard Sandiford wrote:
[snip]
> > -  /* ??? GAS treats single-float processors as though they had 64-bit
> > -     float registers (although it complains when double-precision
> > -     instructions are used).  As things stand, saying they have 32-bit
> > -     registers would lead to spurious "register must be even" messages.
> > -     So here we assume float registers are always the same size as
> > -     integer ones, unless the user says otherwise.  */
> > -  if (file_mips_fp32 < 0)
> > -    file_mips_fp32 = file_mips_gp32;
> > +  switch (file_mips_fp32)
> > +    {
> > +    default:
> > +    case -1:
> > +      /* No user specified float register size.  */
> > +      if (file_mips_gp32 == 0)
> > +	/* 64-bit integer registers implies 64-bit float registers.  */
> > +	file_mips_fp32 = 0;
> > +      else if ((mips_opts.ase_mips3d > 0 || mips_opts.ase_mdmx > 0)
> > +	       && ISA_HAS_64BIT_FPRS (mips_opts.isa))
> > +	/* -mips3d and -mdmx imply 64-bit float registers, if possible.  */
> > +	file_mips_fp32 = 0;
> > +      else
> > +	/* 32-bit float registers. */
> > +	file_mips_fp32 = 1;
> > +      break;
> > +
> > +    /* The user specified the size of the float registers.  Check if it
> > +       agrees with the ABI and ISA.  */
> > +    case 0:
> > +      if (!ISA_HAS_64BIT_FPRS (mips_opts.isa))
> > +	as_bad (_("-mfp64 used with a 32-bit fpu"));
> > +      else if (ABI_NEEDS_32BIT_REGS (mips_abi)
> > +	       && !ISA_HAS_MXHC1 (mips_opts.isa))
> > +	as_warn (_("-mfp64 used with a 32-bit ABI"));
> > +      break;
> > +    case 1:
> > +      if (ABI_NEEDS_64BIT_REGS (mips_abi))
> > +	as_warn (_("-mfp32 used with a 64-bit ABI"));
> > +      break;
> > +    }
> 
> Doesn't the ??? comment still hold?  I thought it would be valuable
> to keep it.

The defaulting is now more complicated than the comment suggests.

> > +  else if (strcmp (name, "gp64") == 0)
> > +    {
> > +      if (!ISA_HAS_64BIT_REGS (mips_opts.isa))
> > +	as_warn ("%s isa does not support 64-bit registers", 
> > +		 mips_cpu_info_from_isa (mips_opts.isa)->name);
> > +      mips_opts.gp32 = 0;
> > +    }
> > +  else if (strcmp (name, "gp32") == 0)
> > +    {
> > +      mips_opts.gp32 = 1;
> > +    }
> > +  else if (strcmp (name, "nogp64") == 0 || strcmp (name, "nogp32") == 0)
> > +    {
> > +      mips_opts.gp32 = file_mips_gp32;
> > +    }
> 
> Ugh.  I don't like the "nogp32" and "nogp64". 

Well, it is what MIPS' SDE toolchain supports.

> All other ".set X"/".set noX"
> pairs are used for turning a particular feature on and off.  Having "nogp32"
> restore the prevailing size (even if that prevailing size _is_ gp32)
> seems very counter-intuitive to me.  Could we not have ".set gp=" instead,
> with a special value to select the prevailing size?  That would be more
> consistent with .set mipsX and .set arch=X, for example.

Hm, .set gp={32,64,default} or .set gp{32,64,0} ?


Thiemo