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From: Andrew Pinski <pinskia@gmail.com> To: Drew Ross <drross@redhat.com> Cc: gcc-bugs@gcc.gnu.org Subject: Re: [PATCH] match.pd: Implement missed optimization (x << c) >> c -> -(x & 1) [PR101955] Date: Thu, 20 Jul 2023 11:08:03 -0700 [thread overview] Message-ID: <CA+=Sn1mFhULxj=SntfePH=9CwVspWFC=sJn6LNjX2uUOELqULA@mail.gmail.com> (raw) In-Reply-To: <CA+=Sn1mMDcOXYWkNRNYE32XPs8SGWR86=PA-9=juR52URbSKVA@mail.gmail.com> On Thu, Jul 20, 2023 at 8:17 AM Andrew Pinski <pinskia@gmail.com> wrote: > > On Thu, Jul 20, 2023 at 7:47 AM Drew Ross via Gcc-bugs > <gcc-bugs@gcc.gnu.org> wrote: > > > > PR middle-end/101955 > > > > gcc/ChangeLog: > > > > * match.pd (x << c) >> c -> -(x & 1): New simplification. > > > > gcc/testsuite/ChangeLog: > > > > * gcc.dg/pr101955.c: New test. > > --- > > gcc/match.pd | 9 +++++ > > gcc/testsuite/gcc.dg/pr101955.c | 62 +++++++++++++++++++++++++++++++++ > > 2 files changed, 71 insertions(+) > > create mode 100644 gcc/testsuite/gcc.dg/pr101955.c > > > > diff --git a/gcc/match.pd b/gcc/match.pd > > index 8543f777a28..bf63652e80f 100644 > > --- a/gcc/match.pd > > +++ b/gcc/match.pd > > @@ -3766,6 +3766,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > > && (wi::ltu_p (wi::to_wide (@1), element_precision (type)))) > > (bit_and @0 (rshift { build_minus_one_cst (type); } @1)))) > > > > +/* Optimize (X << C) >> C where C = precision(type) - 1 and X is signed > > + into -(X & 1). */ > > +(simplify > > + (rshift (lshift @0 INTEGER_CST@1) @@1) > > + (if (ANY_INTEGRAL_TYPE_P (type) > > + && !TYPE_UNSIGNED (type) > > + && wi::eq_p (wi::to_wide (@1), element_precision (type) - 1)) > > + (negate (bit_and @0 { build_one_cst (type); })))) > > I think the lshift does not need to be in the same type but could be > in the unsigned type so you should add a nop_convert? operand there > That is: > (simplify > (rshift (nop_convert? (lshift @0 INTEGER_CST@1)) @@1) > ... > (negate (bit_and (convert @0) { build_one_cst (type); })))) > > Note I see you use INTEGER_CST and then ANY_INTEGRAL_TYPE_P. If you > are going to support vectors, you should use uniform_integer_cst_p > instead of INTEGER_CST and then use uniform_integer_cst_p to get the > constant. Note I just noticed you sent the patch to gcc-bugs@, it really should go to gcc-patches@ . Thanks, Andrew > > Thanks, > Andrew > > > > + > > /* Optimize x >> x into 0 */ > > (simplify > > (rshift @0 @0) > > diff --git a/gcc/testsuite/gcc.dg/pr101955.c b/gcc/testsuite/gcc.dg/pr101955.c > > new file mode 100644 > > index 00000000000..0e233269e21 > > --- /dev/null > > +++ b/gcc/testsuite/gcc.dg/pr101955.c > > @@ -0,0 +1,62 @@ > > +/* { dg-do compile } */ > > +/* { dg-options "-O2 -fdump-tree-dse1 -Wno-psabi" } */ > > + > > +typedef int v4si __attribute__((vector_size(16))); > > + > > +__attribute__((noipa)) int > > +t1 (int x) > > +{ > > + return (x << 31) >> 31; > > +} > > + > > +__attribute__((noipa)) int > > +t2 (int x) > > +{ > > + int y = x << 31; > > + int z = y >> 31; > > + return z; > > +} > > + > > +__attribute__((noipa)) int > > +t3 (int x) > > +{ > > + int w = 31; > > + int y = x << w; > > + int z = y >> w; > > + return z; > > +} > > + > > +__attribute__((noipa)) long long > > +t4 (long long x) > > +{ > > + return (x << 63) >> 63; > > +} > > + > > +__attribute__((noipa)) long long > > +t5 (long long x) > > +{ > > + long long y = x << 63; > > + long long z = y >> 63; > > + return z; > > +} > > + > > +__attribute__((noipa)) long long > > +t6 (long long x) > > +{ > > + int w = 63; > > + long long y = x << w; > > + long long z = y >> w; > > + return z; > > +} > > + > > +__attribute__((noipa)) v4si > > +t7 (v4si x) > > +{ > > + return (x << 31) >> 31; > > +} > > + > > +/* { dg-final { scan-tree-dump-not " >> " "dse1" } } */ > > +/* { dg-final { scan-tree-dump-not " << " "dse1" } } */ > > +/* { dg-final { scan-tree-dump-times " -" 7 "dse1" } } */ > > +/* { dg-final { scan-tree-dump-times " & " 7 "dse1" } } */ > > + > > -- > > 2.39.3 > >
prev parent reply other threads:[~2023-07-20 18:08 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-07-20 14:47 Drew Ross 2023-07-20 14:52 ` Drew Ross 2023-07-20 15:17 ` Andrew Pinski 2023-07-20 18:08 ` Andrew Pinski [this message]
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