Re: [PATCH,MIPS 1/3] Re-work setjmp/longjmp to match o32 FPXX and FP64 ABI

[Steve Ellcey <sellcey at imgtec dot com>]

On Wed, 2014-11-26 at 10:49 +0100, Corinna Vinschen wrote:
> Hi folks,
> 
> Would anybody familiar with MIPS please have a look into Matthew's
> patches?
> 
> 
> Thanks,
> Corinna

Corinna,

I have looked over Matthew's patches and I have also done testing with
the 3 patches, building the mips-mti-elf GCC toolchain and running the
GCC testsuite using these changes.  I will comment on each patch
separately.


> > +#elif __mips_fpr == 0 || __mips_fpr == 64
> > +#define FPR_LAYOUT		\
> > +	and $8, $4, 4;	 	\
> > +	bne $8, $0, 1f;		\
> > +	GPR_OFFSET ($31, 22);	\
> > +	addiu $4, $4, -4;	\
> > +1:				\
> > +	FPR_OFFSET ($f20, 0);  	\
> > +	FPR_OFFSET ($f22, 2);	\
> > +	FPR_OFFSET ($f24, 4);	\
> > +	FPR_OFFSET ($f26, 6);	\
> > +	FPR_OFFSET ($f28, 8);	\
> > +	FPR_OFFSET ($f30, 10);

The only thing I was not sure of with patch 1 is the saving of $31.  I
understand the need for the stack to be 8 byte aligned but I am not sure
why we need to save $31 here and in GPR_LAYOUT.  Can we just align the
stack without saving $31?  I am also not sure how 22 was arrived at as
the offset.

Steve Ellcey
sellcley@imgtec.com