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Re: GCC-How does the coding style affect the insv pattern recognization?
- From: Adam Nemet <adambnemet at gmail dot com>
- To: fanqifei at gmail dot com
- Cc: gcc at gcc dot gnu dot org
- Date: Sun, 17 Jan 2010 15:30:09 -0500
- Subject: Re: GCC-How does the coding style affect the insv pattern recognization?
- References: <f94afa701001120450r7d742609vb45562f02863c6cf@mail.gmail.com>
fanqifei <fanqifei@gmail.com> writes:
> Paolo Bonzini said that insv instruction might be synthesized
> later by combine. But combine only works on at most 3 instructions and
> insv is not generated in such case.
> So exactly when will the insv pattern be recognized and how does
> the coding style affect it?
Sorry for jumping in late. See make_file_assigment in combine.c.
The problem usually is that:
(set A (ior (and B C1) OTHER))
can only be turned into a bit-insertion if A and B happen to be the same
pseudos.
Adam