Re: [Patch] MIPS: mips16e machine patterns - zeb/zeh seb/seh

[Richard Sandiford <rsandifo at nildram dot co dot uk>]

Daniel Jacobowitz <drow@false.org> writes:
> On Fri, Jun 10, 2005 at 10:43:30AM -0700, Eric Christopher wrote:
>> > That's because to be MIPS32/32R2/64/64R2 ASE compliant, the full MIPS16e
>> > set is required, not a subset (MIPS16). I've simply made that if the
>> > user gave -mips16 option for mips_isa>=32, they really mean -mips16e.
>> > As in Ian's previous reply, -march=mips32 -mips16 will imply -mips16e.
>> 
>> Gah. No.
>> 
>> The compiler should not "infer" or "guess" what the user meant. Richard
>> and I spent a lot of time removing that kind of code from the compiler,
>> I don't want to put more in there.
>> 
>> If they say -mips16 they get -mips16. If they say -mips16e they get -
>> mips16e.
>
> This I don't get.  Why not think of it this way (which I thought was
> what Richard was suggesting):
>
>   A MIPS processor with MIPS16 support has two modes, 16-bit and 32-bit
>   instructions.
>
>   When you say -mips16 you get all of the instructions in the selected
>   processor's 16-bit mode.  If -march implies a processor which
>   supports MIPS16e, then enable MIPS16e.

To clear up any confusion, this was indeed what I was suggesting,
but I didn't word it as well.

I just think that -mips16* flags should be _either_ a 16-bit mode
selector _or_ an ISA flag.  David's third option is a bit of a hybrid.

At the moment, -mips16 could be interpreted either way, because gcc
only knows about one 16-bit ISA.

Richard