About the is_gimple_min_invariant predicate

Daniel Berlin dberlin@dberlin.org
Thu Jul 5 14:55:00 GMT 2007

On 7/5/07, Eric Botcazou <ebotcazou@adacore.com> wrote:
> > Note that TREE_INVARIANT is not going to be useful in an IPA world
> > anyway for these users, if it really means that different calls to the
> > function could produce different results.
> We could test TREE_CONSTANT instead and this would be enough to restore Ada
> bootstrap.  But of course the underlying issue would still be there.
> > I'm also not surprised your force_gimple_operand didn't work, since we
> > call force_gimple_operand on the expressions we produce already  :)
> For PRE only as far I can see, not for FRE:

We never insert expressions for FRE, and the replacement we do will
only replace the entire RHS with an SSA_NAME or a constant.

>   /* Insert can get quite slow on an incredibly large number of basic
>      blocks due to some quadratic behavior.  Until this behavior is
>      fixed, don't run it when he have an incredibly large number of
>      bb's.  If we aren't going to run insert, there is no point in
>      computing ANTIC, either, even though it's plenty fast.  */

Also, this should be !do_fre these days.  The comment/test is from a
bygone era long past :)

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