[PATCH] Fix PR11784 - atomic __exchange_and_add() broken for ColdFire targets

[Bernardo Innocenti]

Richard Henderson wrote:
> On Tue, Aug 05, 2003 at 04:27:33PM +0200, Bernardo Innocenti wrote:
> 
>>No, absolutely not. ColdFire cores don't provide the immediate
>>addressing mode for the BSET instruction (probably because it
>>would make the opcode too long for the simplified execution unit).
> 
> But immediate addressing is valid for _some_ instructions
> on ColdFire?  If so, ok...

Actually, it's even more complex than this. BSET has two different
ways to specify the bit number, either as an immediate or as a data
register:

	bset.sz	#bit,<ea>	[1]
	bset.sz	<dreg>,<ea>	[2]
	(sz: .b or .l, no .w!)

With syntax [1], the only allowed addressing modes
for the destination operand on the ColdFire are:

	Dx
	(Ax)
	(Ax)+
	-(Ax)
	(d16,Ax)

With syntax [2], these additional addressing modes are
permitted:

	(d8,Ax,Xi)
	(xxx).w
	(xxx).l

Unless the ColdFire reference manual is wrong, which is
quite possible. In a recent discussion with Peter Barada,
we found a place where Motorola's documentation was quite
incorrect.

-- 
  // Bernardo Innocenti - Develer S.r.l., R&D dept.
\X/  http://www.develer.com/

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