[Patch] libffi-MIPS: More n64 fixes.

Richard Sandiford rsandifo@nildram.co.uk
Fri Dec 7 10:32:00 GMT 2007

David Daney <ddaney@avtrex.com> writes:
> As with my patch from yesterday, this patch  fixes several failures in
> the libffi testsuite caused by the use of a 32 bit add instruction on a
> 64 bit pointer value causing the upper 32 bits to be clobbered.  At the
> same time I took the liberty of converting several 'add a,b,0' to 'move
> a,b'.  Although these were not causing any immediate problems, I think
> it makes the code more understandable.

Agreed.  It also saves worrying about whether the value we're moving
is really a 32-bit one.  However, I couldn't help noticing that all
the moves could be folded into neighbouring instructions.  E.g.:

	REG_L	t4, 3*FFI_SIZEOF_ARG($fp)  # load the flags word
	move	t6, t4			   # and copy it into t6

	and	t4, ((1<<FFI_FLAG_BITS)-1)

simplifies to:

	REG_L	t6, 3*FFI_SIZEOF_ARG($fp)  # load the flags word

	and	t4, t6, ((1<<FFI_FLAG_BITS)-1)

while things like:

	move	t4, t6

simplify to:

	SRL	t4, t6, 1*FFI_FLAG_BITS

As well as being more efficient, it seems slightly more readable
(at least to me).

OK with that change, thanks.


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