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Re: [PATCH RS6000] adding an unsigned SI and a DI together and subtracting an unsigned SI from an DI


>>>>> Richard Henderson writes:

Richard> It'd be nice if the fixed-point exception register was 
Richard> represented in gcc, so you could split these, but...

	The XER register is defined in the machine description, but is not
modeled.  It is unclear how much of a win it is to schedule those
instructions.  XLC does not, for instance.

	What is the current recommendation with regard to use of
gen_lowpart/gen_highpart vs operand_subword vs simplify_gen_subreg?  The
rs6000 port historically has used operand_subword in 32-bit mode, which is
somewhat deprecated but allows the endian option to be described by an
argument.  All variants lead to simplify_gen_subreg.  This patch is using
gen_lowpart/gen_highpart for that purpose.

Thanks, David


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