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Re: Inefficient bitfield code generation
- To: degger at fhm dot edu
- Subject: Re: Inefficient bitfield code generation
- From: David Edelsohn <dje at watson dot ibm dot com>
- Date: Sat, 27 Oct 2001 16:30:18 -0400
- cc: hzoli at austin dot ibm dot com, gcc at gcc dot gnu dot org
>>>>> degger writes:
Daniel> Actually the rs6000 port of gcc is really bad when it
Daniel> comes to using the blazingly powerful rotate and mask
Daniel> instructions of the powerpc.
Daniel> I see several different approaches to cure this performance
Daniel> penalty:
Daniel> - Consider such instructions while optimising in RTL
Daniel> - Have better RTL->insn generators and splitters
Daniel> - Have good peephole definitions
The rs6000 backend has the rotate and mask instructions
well-described, but GCC does not generate the relevant RTL for enough
instances.
David