Re: Re: [PATCH v2] gimple-match.pd Add more optimization for gimple_cond

[Andrew Pinski <pinskia@gmail.com>]

On Mon, Nov 27, 2023 at 10:04 PM Feng Wang <wangfeng@eswincomputing.com> wrote:
>
> On 2023-11-28 11:06  Andrew Pinski <pinskia@gmail.com> wrote:
> >On Mon, Nov 27, 2023 at 6:56 PM Feng Wang <wangfeng@eswincomputing.com> wrote:
> >>
> >> The link of PATCH v1: https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg326661.html
> >> This patch add another condition for gimple-cond optimization. Refer to
> >> the following test case.
> >> int foo1 (int data, int res)
> >> {
> >>   res = data & 0xf;
> >>   res |= res << 4;
> >>   if (res < 0x22)
> >>     return 0x22;
> >>   return res;
> >> }
> >> with the compilation flag "-O2",
> >> before this patch the log info of phiopt2 pass is
> >>   <bb 2> [local count: 1073741824]:
> >>   res_5 = data_1(D) & 15;
> >>   _6 = (unsigned int) res_5;
> >>   _7 = _6 * 17;
> >>   res_8 = (int) _7;
> >>   if (_7 <= 33)
> >>     goto <bb 3>; [21.72%]
> >>   else
> >>     goto <bb 4>; [78.28%]
> >>
> >>   <bb 3> [local count: 233216728]:
> >>
> >>   <bb 4> [local count: 1073741824]:
> >>   # _9 = PHI <res_8(2), 34(3)>
> >>   return _9;
> >> after this patch the the log info of phiopt2 pass is
> >>   <bb 2> [local count: 1073741824]:
> >>   res_5 = data_1(D) & 15;
> >>   _6 = (unsigned int) res_5;
> >>   _7 = _6 * 17;
> >>   res_8 = (int) _7;
> >>   _10 = MAX_EXPR <_7, 34>;
> >>   _3 = (int) _10;
> >>   return _3;
> >> This patch optimizes the phi node to generate "MAX_EXPR".
> >> The root cause of minmax replacement failure is the type of "_7"
> >> is unsigned, but the type of const_int "34" is signed. It makes
> >> types_match (c2_type, from_type) return false. So I add another
> >> condition to process this scenario.
> >>
> >> gcc/ChangeLog:
> >>
> >>         * match.pd: Add another condition to process type mismatch.
> >
> >This should most likely be:
> > ((cond (cmp (convert1? x) c1) (convert2? x) c2) pattern): Also allow
> >conversions that only change the sign.
> >
> >>
> >> gcc/testsuite/ChangeLog:
> >>
> >>         * gcc.dg/tree-ssa/phi-opt-41.c: New test.
> >> ---
> >>  gcc/match.pd                               |  5 ++++-
> >>  gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c | 24 ++++++++++++++++++++++
> >>  2 files changed, 28 insertions(+), 1 deletion(-)
> >>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
> >>
> >> diff --git a/gcc/match.pd b/gcc/match.pd
> >> index 95225e4ca5f..e864845bfa9 100644
> >> --- a/gcc/match.pd
> >> +++ b/gcc/match.pd
> >> @@ -5419,7 +5419,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >>          && (types_match (c2_type, from_type)
> >>              || (TYPE_PRECISION (c2_type) > TYPE_PRECISION (from_type)
> >>                  && (TYPE_UNSIGNED (from_type)
> >> -                    || TYPE_SIGN (c2_type) == TYPE_SIGN (from_type)))))
> >> +                    || TYPE_SIGN (c2_type) == TYPE_SIGN (from_type)))
> >> +             || (TYPE_UNSIGNED (from_type) != TYPE_UNSIGNED (c2_type)
> >> +                 && TYPE_PRECISION (c2_type) == TYPE_PRECISION (from_type)
> >> +                 && !TYPE_OVERFLOW_WRAPS (c2_type))))
> >
> >What is the need for TYPE_OVERFLOW_WRAPS here? Also I think you just
> >need the check for TYPE_PRECISION instead of the rest.
> >Maybe instead of types_match here, tree_nop_conversion_p could be used
> >instead. I am not 100% sure though.
> >
> >I also suspect you should add a few other testcases that don't depend
> >on VRP changing things. Maybe a runtime test too.
> >
> >Thanks,
> >Andrew
> >
>
>
> I want to make sure the cont_int "c2" won't be overflow,so I use the TYPE_OVERFLOW_WRAPS.
That is exactly what the `int_fits_type_p (@2, from_type)` check is
there for in the first place.

Thanks,
Andrew

> I checked the code , tree_nop_conversion_p  judge the TYPE_PRECISION or TYPE_MODE and doesn't
> care the unsigned_flag, it should be fine for this scenario, I'm not sure if there's a problem with this
> modification, I  will run the regression to check whether it causes other issues.


> Thanks,
> Feng Wang
>
>
> >>         {
> >>          if (cmp != EQ_EXPR)
> >>            code = minmax_from_comparison (cmp, @1, @3, @1, @2);
> >> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
> >> new file mode 100644
> >> index 00000000000..d1101c2f9f7
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
> >> @@ -0,0 +1,24 @@
> >> +/* { dg-do compile } */
> >> +/* { dg-options "-O2 -fdump-tree-phiopt2" } */
> >> +
> >> +int foo1 (int data, int res)
> >> +{
> >> +  res = data & 0xf;
> >> +  res |= res << 4;
> >> +  if (res < 0x22)
> >> +    return 0x22;
> >> +  return res;
> >> +}
> >> +
> >> +int foo2 (int data, int res)
> >> +{
> >> +  res = data & 0xf;
> >> +  unsigned int r = res;
> >> +  r*=17;
> >> +  res = r;
> >> +  if (r < 0x22)
> >> +    return 0x22;
> >> +  return res;
> >> +}
> >> +
> >> +/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "phiopt2" } } */
> >> \ No newline at end of file
> >> --
> >> 2.17.1
> >>