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Re: [PATCH v4] Fixups of Loongson2F

Hi, Nick and Richard

Heihaier Just helped to test it and got the building errors:

arch/mips/kernel/genex.S:39: Error: Macro used $at after ".set noat"
arch/mips/kernel/genex.S:43: Error: Macro used $at after ".set noat"

> OK, how's this?  If it looks OK, could someone give it a spin on
> affected Loongson 2F hardware and let me know if it works?  I'd
> especially like to know if the ".set noat" behaviour I was advocating
> breaks current kernel builds.

As the above error shows, this patch really broke the current kernel
builds for lots of places used the following stuff:

.set noat
// use the at register
.set at

for example:

1. arch/mips/kernel/genex.S

.set    noat;                           \   
                PTR_LA  AT, panic;                      \   
                jr      AT;                             \   
9:              b       9b; 

2. arch/mips/kernel/mcount.S



$ grep ".set[[:space:]]noat" -ur arch/mips/ | ...

>   If so, I think the right fix is to let
> the workarounds be switched on and off using ".set", just like you can
> for many other options:
>         .set	push
>         .set    no-fix-loongson2f
>         ...stuff that's known to be safe...
>         .set    pop
> We could then remove the special case for $26 and $27.
> I think this is better than making ".set noat" disable the workarounds.
> ".set noat" is a general feature that can be used by people who don't
> know about this errata, so there's no guarantee that their code is safe.

The ".set no-fix-loongson2f" is a good idea, but since lots of places
have used the ".set noat; /* use AT */; .set at" and we don't know which
places have used this stuff ".set noat; jr AT; .set at", it will be
hard(perhaps we can grep ... and change it) to find out these places to
add the ".set no-fix-loongson2f" and even if we find out them but it
will add lots of loongson specific stuff to the existing source code
which will be more or less ugly.

Best Regards,
	Wu Zhangjin

On Fri, 2010-04-16 at 10:33 +0100, Nick Clifton wrote:
> Hi Richard,
>    [Oops - sorry for taking so long to review this patch].
> > OK, how's this?  If it looks OK, could someone give it a spin on
> > affected Loongson 2F hardware and let me know if it works?
> It looks OK to me, but I do not have access to Loongson hardware to 
> verify it.  Since there has been no response from Wu however I think 
> that you should go ahead and apply it.  If there turns out to be a 
> problem the the ".set noat" behaviour then I am sure that someone will 
> eventually notice it and complain.
> Cheers
>    Nick
> > include/opcode/
> > 	* mips.h (M_JALR_1, M_JALR_2, M_JR, M_NOP): New macro enums.
> >
> > opcodes/
> > 	* mips-opc.c (nop, jr, jalr): Treat as macros.
> >
> > gas/
> > 	* doc/c-mips.texi (-mfix-loongson2f-jump): Be more specific.
> > 	* config/tc-mips.c (mips_fix_loongson2f): Delete.
> > 	(fix_loongson2f_nop, fix_loongson2f_jump, fix_loongson2f): Likewise.
> > 	(append_insn): Don't call mips_fix_loongson2f.
> > 	(append_simple_insn): New function, extracted from...
> > 	(md_assemble):
> > 	(macro_build_nop, modify_jump_target): New functions.
> > 	(macro_build_jalr, macro_build_jr): Likewise.
> > 	(macro_build_jalr): Rename existing function to...
> > 	(macro_build_pic_jalr): ...this.  Add a used_at parameter and use
> > 	the new macro_build_jalr.
> > 	(load_delay_nop): Use macro_build_nop.
> > 	(load_address): Likewise.
> > 	(macro): Use macro_build_nop, macro_build_jr and macro_build_jalr.
> > 	Handle M_NOP, M_JR, M_JALR_1 and M_JALR_2.  Update calls to what
> > 	is now macro_build_pic_jalr.
> > 	(macro2): Likewise.
> > 	(md_parse_option): Don't set mips_fix_loongson2f.
> >
> > gas/testsuite/
> > 	* gas/mips/loongson-2f-2.s: Swap the explicit and implicit cases.
> > 	Add tests for various macro modes.
> > 	* gas/mips/loongson-2f-3.s: Test J, JR, single-operand JA{L,}R and
> > 	double-operand JA{L,}R for both the "fix" and "no fix" cases.
> > 	* gas/mips/loongson-2f-3.d: Require -mips1 -mabi=32.  Update after
> > 	above changes.
> > 	* gas/mips/loongson-2f-4.s, gas/mips/loongson-2f-4.d,
> > 	gas/mips/loongson-2f-4.l, gas/mips/loongson-2f-5.s,
> > 	gas/mips/loongson-2f-5.l: New tests.
> > 	* gas/mips/mips.exp: Run them.

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