RE: [MIPS] Add new virtualization instructions

["Maciej W. Rozycki" <macro at codesourcery dot com>]

On Thu, 13 Jun 2013, Chao-Ying Fu wrote:

> >  Why do you need to change it?  It's proved useful in finding 
> > bugs -- ASEs 
> > that should be made available to microMIPS assembly 
> > unconditionally such 
> > as with the EVA support discussed as recently as yesterday.
> 
>   If I add -mips64r2 to the as flag for the micromips@virt64.d test,
> I will get this error.
> 
> Ex:  micromips@virt64.d
> #objdump: -dr --prefix-addresses  --show-raw-insn -Mvirt,cp0-names=mips64r2
> #name: virt64 instructions
> #source: virt64.s
> #as: -64 -mvirt -mips64r2
> ....
> 
> Ex: Testing
> ../as-new  -64 -mvirt -mips64r2 -march=mips64 -mmicromips -o dump.o /home/fu/dev
> /gcc-mainline/src/gas/testsuite/gas/mips/virt64.s
> Executing on host: sh -c {../as-new  -64 -mvirt -mips64r2 -march=mips64 -mmicrom
> ips -o dump.o /home/fu/dev/gcc-mainline/src/gas/testsuite/gas/mips/virt64.s 2>&1
> }  /dev/null gas.out (timeout = 300)
> Assembler messages:
> Error: -mips64r2 conflicts with the other architecture options, which imply -mip
> s64
> /home/fu/dev/gcc-mainline/src/gas/testsuite/gas/mips/virt64.s:5: Error: Opcode n
> ot supported on this processor: mips64 (mips64) `dmfgc0 $3,$29'
> ....
> 
>   Or, if I change ISA_SUPPORTS_VIRT64_ASE to support micromips with MIPS64,
> I won't need the mips64r2 change in mips.exp and the micromips virt64 
> test will run.
> Ex:
> Index: config/tc-mips.c
> ===================================================================
> RCS file: /cvs/src/src/gas/config/tc-mips.c,v
> retrieving revision 1.538
> diff -u -p -r1.538 tc-mips.c
> --- config/tc-mips.c	10 Jun 2013 18:15:47 -0000	1.538
> +++ config/tc-mips.c	13 Jun 2013 17:37:10 -0000
> @@ -381,9 +381,12 @@ static int file_ase_mt;
>  static int file_ase_virt;
>  
>  #define ISA_SUPPORTS_VIRT_ASE (mips_opts.isa == ISA_MIPS32R2		\
> -			       || mips_opts.isa == ISA_MIPS64R2)
> +			       || mips_opts.isa == ISA_MIPS64R2		\
> +			       || mips_opts.micromips)
>  
> -#define ISA_SUPPORTS_VIRT64_ASE (mips_opts.isa == ISA_MIPS64R2)
> +#define ISA_SUPPORTS_VIRT64_ASE (mips_opts.isa == ISA_MIPS64R2		\
> +				 || (mips_opts.isa == ISA_MIPS64	\
> +				     && mips_opts.micromips))
>  
>  /* The argument of the -march= flag.  The architecture we are assembling.  */
>  static int file_mips_arch = CPU_UNKNOWN;
> 
>   Are there other solutions to let the micromips virt64 test run?

 Thanks, I can see what you mean now -- essentially VIRT64 is the first 
strictly microMIPS64 feature we're going to support.  The issue looks to 
me like the outcome of a previous decision to make -mips3 switch microMIPS 
assembly into the 64-bit mode.  I believe this was your own decision too, 
:) that we accepted.  I think we can stick to it and just as we already 
enable all the optional microMIPS32 features for -mips1 assembly we do the 
same for microMIPS64 and -mips3 assembly.

 Given the above how about:

#define ISA_SUPPORTS_VIRT64_ASE (mips_opts.isa == ISA_MIPS64R2
				 || (mips_opts.micromips
				     && ISA_HAS_64BIT_REGS (mips_opts.isa)))

?  We'll then do the same if e.g. DSP64 is added to the microMIPS 
instruction set.

  Maciej