GCC-How does the coding style affect the insv pattern recognization?

[Adam Nemet]

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