Re: Why pass HAVE_32BIT_GPRS to OPCODE_IS_MEMBER?

["H . J . Lu" <hjl at lucon dot org>]

On Tue, Aug 07, 2001 at 09:14:36PM +0100, Richard Sandiford wrote:
> "H . J . Lu" <hjl@lucon.org> writes:
> 
> > The new gas generates different opcodes on Linux/mips. The change was
> > introduced by the HAVE_32BIT_GPRS change. In include/opcode/mips.h
> > 
> > /* Test for membership in an ISA including chip specific ISAs.
> >    INSN is pointer to an element of the opcode table; ISA is the
> >    specified ISA to test against; and CPU is the CPU specific ISA
> >    to test, or zero if no CPU specific ISA test is desired.
> >    The gp32 arg is set when you need to force 32-bit register usage on
> >    a machine with 64-bit registers; see the documentation under -mgp32
> >    in the MIPS gas docs.  */
> > 
> > #define OPCODE_IS_MEMBER(insn, isa, cpu, gp32)                          \
> > 
> > I don't understand why the change was made. Here is a patch which
> > restores the old opcodes. But I am not sure if it is 100% correct.
> > Any comments?
> 
> I'm not sure why you want to make this change.  Because you want "addi" to be
> used instead of "ori" for the move instruction?  It should be OK to change

It is "addu" vs. "or" for "move $1, $2".

> mips-opc.c so that "addi" is used for -mgp32 if so.
> 
> There was discussion after I sent the patch of making the mtune option
> decide which instruction is used for moves.  That sounded like a great idea,
> so I held off making a mips-opc.c change myself.
> 
> Your patch seems to assume that "-mips2" and "-mips2 -mgp32" should give
> different results, which doesn't make much sense to me.

That was the old behavior, which I don't know if it makes senses or not. That
is why I am asking. Maybe we should do

#define HAVE_FORCEED_32BIT_GPRS			\
   ((mips_gp32 || mips_32bit_abi)		\
    && ISA_HAS_64BIT_REGS (mips_opts.isa))

I cannot tell any difference between "addu" vs. "or" for "move". But I
don't think we should change it for no good reason.


H.J.