[Bug tree-optimization/63743] Thumb1: big regression for float operators by r216728

["zhenqiang.chen at arm dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63743

--- Comment #4 from Zhenqiang Chen <zhenqiang.chen at arm dot com> ---
(In reply to Jakub Jelinek from comment #3)
> (In reply to Zhenqiang Chen from comment #2)
> > (In reply to Jakub Jelinek from comment #1)
> > > Were we swapping operands before?  I mean, if you rewrite the testcase to
> > > swap the * arguments in the source, did you get the same more efficient code
> > > in the past?
> > 
> > Yes. I tried the test case:
> > 
> > double
> > test1 (double x, double y)
> > {
> >   return x * (x + y);
> > }
> > double
> > test2 (double x, double y)
> > {
> >   return (x + y) * x;
> > }
> > 
> > Without r216728, I got efficient codes for both functions. But with r216728,
> > I got inefficient codes for both functions.
> 
> What about
> double
> test3 (double x, double y)
> {
>   return (x + y) * (x - y);
> }
> ?  At least from quick looking at ppc -msoft-float -O2 -m32, I see the same
> issue there, add called first, sub called second, and result of second
> returned in the same registers as used for the first argument. So something
> to handle at expansion or RA rather than in GIMPLE anyway IMHO.

Same issue for the case on Thumb1.