Combine known_cond() may create subreg of const_int

Richard Henderson rth@redhat.com
Tue Feb 12 13:49:00 GMT 2002


On Mon, Feb 11, 2002 at 08:58:50AM -0200, Alexandre Oliva wrote:
> However, I wonder if it would be best to fold this logic into do_SUBST,
> and/or to handle ZERO_EXTEND and SIGN_EXTEND similarly.  Is this ok to
> install?

It would be good to handle zero/sign extend.

The option of hooking into do_SUBST is interesting, but I wonder if it'll
sometimes be too late.  That is, we'll have made some simplifications
based on the value being 171, when it ought to have been the QImode -85.

Certainly we can put an assertion in do_SUBST that the replaced constant
must match the mode of the thing it replaced.  I wonder how many problems
that will expose?

> 	* combine.c (known_cond): After replacing the REG of a SUBREG, try
> 	to simplify it.

Ok.


r~



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