Re: [V2 PATCH] Handle bitop with INTEGER_CST in analyze_and_compute_bitop_with_inv_effect.

[Hongtao Liu <crazylht@gmail.com>]

On Tue, Nov 7, 2023 at 4:10 PM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Tue, Nov 7, 2023 at 7:08 AM liuhongt <hongtao.liu@intel.com> wrote:
> >
> > analyze_and_compute_bitop_with_inv_effect assumes the first operand is
> > loop invariant which is not the case when it's INTEGER_CST.
> >
> > Bootstrapped and regtseted on x86_64-pc-linux-gnu{-m32,}.
> > Ok for trunk?
>
> So this addresses a missed optimization, right?  It seems to me that
> even with two SSA names we are only "lucky" when rhs1 is the invariant
> one.  So instead of swapping this way I'd do
Yes, it's a miss optimization.
And I think expr_invariant_in_loop_p (loop, match_op[1]) should be
enough, if match_op[1] is a loop invariant.it must be false for the
below conditions(there couldn't be any header_phi from its
definition).

>
>  unsigned i;
>  for (i = 0; i < 2; ++i)
>    if (TREE_CODE (match_op[i]) == SSA_NAME
>        && ...)
>     break; /* found! */
>
>   if (i == 2)
>     return NULL_TREE;
>   if (i == 0)
>     std::swap (match_op[0], match_op[1]);
>
> to also handle a "swapped" pair of SSA names?
>
> > gcc/ChangeLog:
> >
> >         PR tree-optimization/105735
> >         PR tree-optimization/111972
> >         * tree-scalar-evolution.cc
> >         (analyze_and_compute_bitop_with_inv_effect): Handle bitop with
> >         INTEGER_CST.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * gcc.target/i386/pr105735-3.c: New test.
> > ---
> >  gcc/testsuite/gcc.target/i386/pr105735-3.c | 87 ++++++++++++++++++++++
> >  gcc/tree-scalar-evolution.cc               |  3 +
> >  2 files changed, 90 insertions(+)
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr105735-3.c
> >
> > diff --git a/gcc/testsuite/gcc.target/i386/pr105735-3.c b/gcc/testsuite/gcc.target/i386/pr105735-3.c
> > new file mode 100644
> > index 00000000000..9e268a1a997
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr105735-3.c
> > @@ -0,0 +1,87 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O1 -fdump-tree-sccp-details" } */
> > +/* { dg-final { scan-tree-dump-times {final value replacement} 8 "sccp" } } */
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +foo (unsigned int tmp)
> > +{
> > +  for (int bit = 0; bit < 64; bit++)
> > +    tmp &= 11304;
> > +  return tmp;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +foo1 (unsigned int tmp)
> > +{
> > +  for (int bit = 63; bit >= 0; bit -=3)
> > +    tmp &= 11304;
> > +  return tmp;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +foo2 (unsigned int tmp)
> > +{
> > +  for (int bit = 0; bit < 64; bit++)
> > +    tmp |= 11304;
> > +  return tmp;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +foo3 (unsigned int tmp)
> > +{
> > +  for (int bit = 63; bit >= 0; bit -=3)
> > +    tmp |= 11304;
> > +  return tmp;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +foo4 (unsigned int tmp)
> > +{
> > +  for (int bit = 0; bit < 64; bit++)
> > +    tmp ^= 11304;
> > +  return tmp;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +foo5 (unsigned int tmp)
> > +{
> > +  for (int bit = 0; bit < 63; bit++)
> > +    tmp ^= 11304;
> > +  return tmp;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +f (unsigned int tmp, int bit)
> > +{
> > +  unsigned int res = tmp;
> > +  for (int i = 0; i < bit; i++)
> > +    res &= 11304;
> > +  return res;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +f1 (unsigned int tmp, int bit)
> > +{
> > +  unsigned int res = tmp;
> > +  for (int i = 0; i < bit; i++)
> > +    res |= 11304;
> > +  return res;
> > +}
> > +
> > +unsigned int
> > +__attribute__((noipa))
> > +f2 (unsigned int tmp, int bit)
> > +{
> > +  unsigned int res = tmp;
> > +  for (int i = 0; i < bit; i++)
> > +    res ^= 11304;
> > +  return res;
> > +}
> > diff --git a/gcc/tree-scalar-evolution.cc b/gcc/tree-scalar-evolution.cc
> > index 70b17c5bca1..f61277c32df 100644
> > --- a/gcc/tree-scalar-evolution.cc
> > +++ b/gcc/tree-scalar-evolution.cc
> > @@ -3689,6 +3689,9 @@ analyze_and_compute_bitop_with_inv_effect (class loop* loop, tree phidef,
> >    match_op[0] = gimple_assign_rhs1 (def);
> >    match_op[1] = gimple_assign_rhs2 (def);
> >
> > +  if (expr_invariant_in_loop_p (loop, match_op[1]))
> > +    std::swap (match_op[0], match_op[1]);
> > +
> >    if (TREE_CODE (match_op[1]) != SSA_NAME
> >        || !expr_invariant_in_loop_p (loop, match_op[0])
> >        || !(header_phi = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (match_op[1])))
> > --
> > 2.31.1
> >



-- 
BR,
Hongtao