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List:       binutils
Subject:    Re: Power4 should treat mftb as extended mfspr mnemonic
From:       Segher Boessenkool <segher () kernel ! crashing ! org>
Date:       2014-11-30 18:02:09
Message-ID: 20141130180209.GA31176 () gate ! crashing ! org
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On Sun, Nov 30, 2014 at 01:36:55PM +1030, Alan Modra wrote:
> On Fri, Nov 28, 2014 at 02:34:54PM +1030, Alan Modra wrote:
> > mftb is marked phased out in the architecture manual, but we can keep
> > it as an extended mnemonic for mftbl.
> 
> On further reading of ISA manual it appears gas should have been
> treating mftb and mftbu as extended mnemonics for mfspr, for ISA 2.03
> and later.  The 31,371 opcode is phased out, not the mnemonic.
> 
> opcodes/
> 	* ppc-opc.c (powerpc_opcodes): Make mftb* generate mfspr for
> 	power4 and later.

Does that work with current GCC (for its mftb builtins)?  I.e. what
does this do with -many, does it generate mftb or mfspr insns?


> - 4b4:	(7c 6c 42 e6|e6 42 6c 7c) 	mftbl   r3
> + 4b4:	(7c 6c 42 a6|a6 42 6c 7c) 	mftb    r3

Nice to see this nuisance finally fixed.  Although, only for 476 and a2?


Segher

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