[Patch, mips] Fix compiler abort with -mips32r2 -mips16 -msynci

[Steve Ellcey]

On Wed, 2012-07-18 at 18:30 +0100, Richard Sandiford wrote:

> The abort sounds like the bug here.  It's deliberate that things like
> -msynci, -mbranch-likely, etc., are OK with -mips16.  On the one hand,
> you could compile with -mips16 but have an __attribute__((nomips16))
> function that could benefit from using SYNCI.  On the other, you could
> compile without -mips16 but have an __attribute__((mips16)) function
> that needs to avoid SYNCI.

OK, I think that makes sense.

> -mips16 really just sets the default ISA mode for functions that don't
> specify one.  That's why override_options hides mips16ness so early on,
> like you say.

Ah, I didn't really understand why we were hiding the -mips16 setting,
now I do.

I will see if I can figure out why we abort.  The clear_cache insn in
mips.md looks a bit odd to me, there is the part that is executed when
TARGET_SYNCI is true and then a part that is only executed if
mips_cache_flush_func is defined.  It looks like if
mips_cache_flush_func is not defined then we do nothing and I was
wondering if that is correct or not?  Should mips_cache_flush_func
being NULL be an error?  I am not even sure if you can make it NULL
given that it is given a default value in mips.opt.

My test case is:

void f()
{
  int size = 40;
  char *memory = __builtin_alloca(size);
  __builtin___clear_cache(memory, memory + size);
}


And the abort with -mips32r2 -mips16 -msynci is:

x.c: In function ‘f’:
x.c:6:1: error: unrecognizable insn:
 }
 ^
(jump_insn 22 21 38 2 (set (pc)
        (if_then_else (eq (reg:SI 207)
                (reg/f:SI 196 [ D.1415 ]))
            (label_ref 33)
            (pc))) x.c:5 -1
     (nil)
 -> 33)
x.c:6:1: internal compiler error: in extract_insn, at recog.c:2129
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.


If I can't figure out what is going on I will file a bug report.

Steve Ellcey
sellcey@mips.com