Re: [RFA] mips: Fix "info registers" output

[Andrew Cagney <ac131313@cygnus.com>]

> Meanwhile, Andrew, is this trivial fix OK?  It just makes us decode the
> actual register values instead of two host pointers in our call to
> unpack_double.

I suspect the code was more broken then you thought!

If my memory is correct, the value is always stored LE in the register 
pair.  The code manages to do a double swap and consequently doesn't 
correctly re-order the registers in the dbl_buffer.

It is also really broken when a 32 bit ABI is on a 64 bit ISA.  (It very 
nearly corrupts the stack).

>  /* copy the two floats into one double, and unpack both */
> -      memcpy (dbl_buffer, raw_buffer, 2 * REGISTER_RAW_SIZE (FP0_REGNUM));
>        flt1 = unpack_double (builtin_type_float, raw_buffer[HI], &inv1);
>        flt2 = unpack_double (builtin_type_float, raw_buffer[LO], &inv2);
> +      memcpy (dbl_buffer, raw_buffer[HI], REGISTER_RAW_SIZE (FP0_REGNUM));
> +      memcpy (dbl_buffer + REGISTER_RAW_SIZE (FP0_REGNUM),
> +	      raw_buffer[LO], REGISTER_RAW_SIZE (FP0_REGNUM));
>        doub = unpack_double (builtin_type_double, dbl_buffer, &inv3);
>  

I suspect a bigger improvement would look something like (I'm still not 
100% sure of what goes where with BE/LE though :-)

if (!FP_REGISTER_DOUBLE)
   char *raw_buffer[2];
   char *dbl_buffer;
   raw_buffer[0] = alloca; [1] = alloca; dbl_buffer = alloca;
   read_relative_register(regnum+0, raw_buffer[0])
   read_relative_register(regnum+1, raw_buffer[1])
   if (BE)
     reg_offset = (REGISTER_RAW_SIZE() == 8) ? 4 : 0;
     type_float = builtin_type_ieee_single_big
     type_double = builtin_type_ieee_double_big
     memcpy dbl_buffer+4, raw_buffer[0] + reg_offset, 4);
     memcpy dbl_buffer+0, raw_buffer[1] + reg_offset, 4);
   else
     reg_offset = 0
     type_float = builtin_type_ieee_single_little
     type_double = builtin_type_ieee_double_little
     memcpy dbl_buffer+0, raw_buffer[0] + reg_offset, 4);
     memcpy dbl_buffer+4, raw_buffer[1] + reg_offset, 4);
   flt0 = unpack_double (type_float, raw_buffer[0] + reg_offset, &inv)
   flt1 = unpack_double (type_float, raw_buffer[1] + reg_offset, &inv)
   doub = unpack_double (type_double, dbl_buffer, &inv3)


Andrew