[RFA][PATCH][pr target/60648] Fix non-canonical RTL from x86 backend -- P1 regression

[Jakub Jelinek]

On Wed, Mar 26, 2014 at 12:17:43PM -0600, Jeff Law wrote:
> On 03/26/14 12:12, Jakub Jelinek wrote:
> >On Wed, Mar 26, 2014 at 11:02:48AM -0600, Jeff Law wrote:
> >>Bootstrapped and regression tested on x86_64-unknown-linux-gnu.
> >>Verified it fixes the original and reduced testcase.
> >
> >Note, the testcase is missing from your patch.
> >
> >But I'd question if this is the right place to canonicalize it.
> >The non-canonical order seems to be created in the generic code, where
> >do_tablejump does:
> No, at that point it's still canonical because the x86 backend
> hasn't simpified the (mult ...) subexpression.  Its the
> simplification of that subexpression to a constant that creates the
> non-canonical RTL.  That's why I fixed the x86 bits -- those are the
> bits that simplify the (mult ...) into a (const_int) and thus
> creates the non-canonical RTL.

(mult:SI (const_int 0) (const_int 4)) is IMHO far from being canonical.
And, I'd say it is likely other target legitimization hooks would also try
to simplify it similarly.
simplify_gen_binary is used in several other places during expansion,
so I don't see why it couldn't be desirable here.

	Jakub