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[PATCH] Add MIPS32r2/MT ASE pause instruction

Richard Sandiford rdsandiford@googlemail.com
Thu Dec 8 19:52:00 GMT 2011 
"Maciej W. Rozycki" <macro@linux-mips.org> writes:
>> Index: opcodes/mips-opc.c
>> ===================================================================
>> RCS file: /cvs/src/src/opcodes/mips-opc.c,v
>> retrieving revision 1.89
>> diff -u -p -r1.89 mips-opc.c
>> --- opcodes/mips-opc.c	29 Nov 2011 20:28:55 -0000	1.89
>> +++ opcodes/mips-opc.c	7 Dec 2011 22:39:50 -0000
>> @@ -1169,6 +1169,7 @@ const struct mips_opcode mips_builtin_op
>>  {"ori",     "t,r,i",	0x34000000, 0xfc000000,	WR_t|RD_s,		0,		I1	},
>>  {"pabsdiff.ob", "X,Y,Q",0x78000009, 0xfc20003f,	WR_D|RD_S|RD_T|FP_D,	0,		SB1	},
>>  {"pabsdiffc.ob", "Y,Q",	0x78000035, 0xfc2007ff,	RD_S|RD_T|FP_D,		WR_MACC,	SB1	},
>> +{"pause",   "",		0x00000140, 0xffffffff, TRAP,			0,		I33|MT32},
>>  {"pavg.ob", "X,Y,Q",	0x78000008, 0xfc20003f,	WR_D|RD_S|RD_T|FP_D,	0,		SB1	},
>>  {"pickf.ob", "X,Y,Q",	0x78000002, 0xfc20003f,	WR_D|RD_S|RD_T|FP_D,	0,		MX|SB1	},
>>  {"pickf.ob", "D,S,T",	0x4ac00002, 0xffe0003f,	WR_D|RD_S|RD_T,		0,		N54	},
>
>  I think it's redundant to say |MT32 here as MT32 already implies I33 -- 
> the MT ASE requires rev. 2 of the architecture.
>
>  Also please use NODS rather than TRAP -- although both macros expand to 
> the same numerical value, they have been semantically split so that the 
> former refers to instructions that must not be scheduled into a delay slot 
> for architectural reasons (undefined behaviour) and the latter is for 
> instructions that are meant to generate a trap and we chose not to 
> schedule these instructions into a delay slot merely to make life of other 
> software easier (delay-slot execution is just fine).
>
>  Yes, I know most MT instructions use the TRAP flag, but that's because 
> there's really no reason I know of they should have this flag at all in 
> the first place, so they have been left as classified "for someone's 
> convenience" (some can legitimately trap indeed, i.e. FORK when run out of 
> thread contexts).  PAUSE's delay-slot operation is on the other hand 
> undefined (which actually brings a concern about forward compatibility of 
> old software, hmm...).
>
>  I can't approve the change, but it looks good to me otherwise.

OK with Maciej's changes (i.e. MT32 rather than "I33|MT32" and
NODS rather than TRAP).

Richard
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