biarch support for 2.6, missing kdb pieces

David Edelsohn dje at
Wed Oct 15 12:10:20 EST 2003

>>>>> Anton Blanchard writes:

Anton> It makes sense to optimise for POWER4 in the default kernel. Up until
Anton> recently -mcpu=POWER4 would tune for it but would still run on RS64 and
Anton> POWER3.

Anton> Unfortunately the mtcrf optimisation in POWER4 results in an illegal
Anton> instruction on POWER3.

	Cool!  I'm glad the test and optimization is working.

	The GCC -mtune=power4 option allows one to schedule for POWER4 but
generate instructions for default architecture.

Anton> Alan: BTW is there an extended format for mtcrf? I was optimising some
Anton> POWER4 only assembly in the kernel and figured we could safely use the
Anton> extended mtcrf there.

	There is a proposed extended mnemonic, but it is not widely
implemented yet.  The assembler is suppose to recognize when a single
field is moved.


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