Re: mipsisa32-unknown-elf-as: Error: too large constant specified

[Nigel Stephens <nigel at mips dot com>]

Ian Lance Taylor wrote:

> Hey, I'm easy.  Any opinions on this patch?  I haven't tried the
> testsuite yet.  In any case, clearly some new tests are called for
> here.
>
>  

I'm happy with it. But note that this doesn't return the behaviour to 
what cgd was seeing on the old assembler when compiling for a 64-bit 
ISA. It will now compile

       or      $2, $2, 0xe0000000
       and     $2, $2, ~0xe0000000

to the same sequence for both a 32 and 64-bit arch:

  0:   3c01e000        lui     at,0xe000
  4:   00411025        or      v0,v0,at
  8:   3c011fff        lui     at,0x1fff
  c:   3421ffff        ori     at,at,0xffff
 10:   00411024        and     v0,v0,at

But I'd claim that's correct: it's not sensible for the assembler to interpret immediate operands differently depending on the architecture. It should only interpret immediates as truly 64-bit if they are used with explicit 64-bit instructions (e.g. daddu, dli, etc), which is what this patch will do.

Ian wrote:

> With the patch I sent out, code like this will assemble without a
> warning on a 32-bit target:
> 	and	$2, $2, 0xffffffffe0000000
> which is somewhat dubious.


Oh I don't know - that's a valid 32-bit immediate with 64-bit sign extension. The more ugly thing is that it would allow:

	and	$2,$2,0xffffffff1f000000 

But I'm prepared to look the other way if you are. :-)

Nigel