On Wed, 25 May 2022, David Malcolm wrote:
> On Wed, 2022-05-25 at 10:36 +0200, Richard Biener via Gcc-patches
> wrote:
> > This patch adds support to unswitch loops with switch statements
> > based on invariant index. It furthermore reworks the cost model
> > to allow an overall budget of statements to be created per original
> > loop by all unswitching opportunities in the loop. Compared to
> > the original all unswitching opportunities in a loop are
> > pre-evaluated before the first transform which will allow future
> > changes to select the most profitable candidates first.
> >
> > To efficiently support switch statements the pass now uses
> > ranger to simplify switch statements and conditions in loop
> > copies based on ranges extracted from the recorded set of
> > predicates unswitched.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed to trunk.
> >
> > Richard.
> >
>
> [...snip...]
>
> > diff --git a/gcc/testsuite/gcc.dg/loop-unswitch-10.c
> > b/gcc/testsuite/gcc.dg/loop-unswitch-10.c
> > new file mode 100644
> > index 00000000000..5e4f16e2935
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/loop-unswitch-10.c
> > @@ -0,0 +1,56 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -funswitch-loops -fdump-tree-unswitch-
> > optimized" } */
> > +
> > +int
> > +__attribute__((noipa))
> > +foo(double *a, double *b, double *c, double *d, double *r, int size,
> > int order)
> > +{
> > + for (int i = 0; i < size; i++)
> > + {
> > + double tmp, tmp2;
> > +
> > + switch(order)
> > + {
> > + case 0:
> > + tmp = -8 * a[i];
> > + tmp2 = 2 * b[i];
> > + break;
> > + case 1:
> > + tmp = 3 * a[i] - 2 * b[i];
> > + tmp2 = 5 * b[i] - 2 * c[i];
> > + break;
> > + case 2:
> > + tmp = 9 * a[i] + 2 * b[i] + c[i];
> > + tmp2 = 4 * b[i] + 2 * c[i] + 8 * d[i];
> > + break;
> > + case 3:
> > + tmp = 3 * a[i] + 2 * b[i] - c[i];
> > + tmp2 = b[i] - 2 * c[i] + 8 * d[i];
> > + break;
> > + defaut:
> > + __builtin_unreachable ();
>
> I'm guessing "defaut:" here is a typo for "default:" i.e. it's an
> unused label named "defaut", when presumably you meant to have an
> unreachable default case. Does this affect the loop unswitching logic?
>
> I wonder if we warn for this (or if we can/should?)
I guess we might want to (warn about labels in the "toplevel"
scope in switch statements). So warn about
switch (x)
{
case 1:
bar:
};
the 'case' might be missing here (if 'bar' is a valid enumeration
constant for example) but not about
switch (x)
{
case 1:
{
bar:
}
};
Maybe we just want to warn when the label is otherwise unused?
> Looking at the patch, it seems to also be present in:
> gcc/testsuite/gcc.dg/loop-unswitch-11.c
> gcc/testsuite/gcc.dg/loop-unswitch-14.c
> but I might have missed some.
Heh - how did you spot these but me not looking over the patch
multiple times ...
And no, it doesn't change behavior so I just pushed a fix.
Richard.
>
>
> Dave
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)
