[v2] Simplify memchr with small constant strings

  When memchr is applied on a constant string of no more than the bytes of
a word, simplify memchr by checking each byte in the constant string.

int f (int a)
{
   return  __builtin_memchr ("AE", a, 2) != 0;
}

is simplified to

int f (int a)
{
  return ((char) a == 'A' || (char) a == 'E') != 0;
}

gcc/

	PR tree-optimization/103798
	* tree-ssa-forwprop.cc: Include "tree-ssa-strlen.h".
	(simplify_builtin_call): Inline memchr with constant strings of
	no more than the bytes of a word.
	* tree-ssa-strlen.cc (use_in_zero_equality): Make it global.
	* tree-ssa-strlen.h (use_in_zero_equality): New.

gcc/testsuite/

	PR tree-optimization/103798
	* c-c++-common/pr103798-1.c: New test.
	* c-c++-common/pr103798-2.c: Likewise.
	* c-c++-common/pr103798-3.c: Likewise.
	* c-c++-common/pr103798-4.c: Likewise.
	* c-c++-common/pr103798-5.c: Likewise.
	* c-c++-common/pr103798-6.c: Likewise.
	* c-c++-common/pr103798-7.c: Likewise.
	* c-c++-common/pr103798-8.c: Likewise.
---
 gcc/testsuite/c-c++-common/pr103798-1.c | 28 +++++++++++
 gcc/testsuite/c-c++-common/pr103798-2.c | 30 ++++++++++++
 gcc/testsuite/c-c++-common/pr103798-3.c | 28 +++++++++++
 gcc/testsuite/c-c++-common/pr103798-4.c | 28 +++++++++++
 gcc/testsuite/c-c++-common/pr103798-5.c | 26 ++++++++++
 gcc/testsuite/c-c++-common/pr103798-6.c | 27 +++++++++++
 gcc/testsuite/c-c++-common/pr103798-7.c | 27 +++++++++++
 gcc/testsuite/c-c++-common/pr103798-8.c | 27 +++++++++++
 gcc/tree-ssa-forwprop.cc                | 64 +++++++++++++++++++++++++
 gcc/tree-ssa-strlen.cc                  |  4 +-
 gcc/tree-ssa-strlen.h                   |  2 +
 11 files changed, 289 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-1.c
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-2.c
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-3.c
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-4.c
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-5.c
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-6.c
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-7.c
 create mode 100644 gcc/testsuite/c-c++-common/pr103798-8.c
  

On Thu, Jul 7, 2022 at 6:45 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> When memchr is applied on a constant string of no more than the bytes of
> a word, simplify memchr by checking each byte in the constant string.
>
> int f (int a)
> {
>    return  __builtin_memchr ("AE", a, 2) != 0;
> }
>
> is simplified to
>
> int f (int a)
> {
>   return ((char) a == 'A' || (char) a == 'E') != 0;
> }
>
> gcc/
>
>         PR tree-optimization/103798
>         * tree-ssa-forwprop.cc: Include "tree-ssa-strlen.h".
>         (simplify_builtin_call): Inline memchr with constant strings of
>         no more than the bytes of a word.
>         * tree-ssa-strlen.cc (use_in_zero_equality): Make it global.
>         * tree-ssa-strlen.h (use_in_zero_equality): New.
>
> gcc/testsuite/
>
>         PR tree-optimization/103798
>         * c-c++-common/pr103798-1.c: New test.
>         * c-c++-common/pr103798-2.c: Likewise.
>         * c-c++-common/pr103798-3.c: Likewise.
>         * c-c++-common/pr103798-4.c: Likewise.
>         * c-c++-common/pr103798-5.c: Likewise.
>         * c-c++-common/pr103798-6.c: Likewise.
>         * c-c++-common/pr103798-7.c: Likewise.
>         * c-c++-common/pr103798-8.c: Likewise.
> ---
>  gcc/testsuite/c-c++-common/pr103798-1.c | 28 +++++++++++
>  gcc/testsuite/c-c++-common/pr103798-2.c | 30 ++++++++++++
>  gcc/testsuite/c-c++-common/pr103798-3.c | 28 +++++++++++
>  gcc/testsuite/c-c++-common/pr103798-4.c | 28 +++++++++++
>  gcc/testsuite/c-c++-common/pr103798-5.c | 26 ++++++++++
>  gcc/testsuite/c-c++-common/pr103798-6.c | 27 +++++++++++
>  gcc/testsuite/c-c++-common/pr103798-7.c | 27 +++++++++++
>  gcc/testsuite/c-c++-common/pr103798-8.c | 27 +++++++++++
>  gcc/tree-ssa-forwprop.cc                | 64 +++++++++++++++++++++++++
>  gcc/tree-ssa-strlen.cc                  |  4 +-
>  gcc/tree-ssa-strlen.h                   |  2 +
>  11 files changed, 289 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-1.c
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-2.c
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-3.c
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-4.c
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-5.c
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-6.c
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-7.c
>  create mode 100644 gcc/testsuite/c-c++-common/pr103798-8.c
>
> diff --git a/gcc/testsuite/c-c++-common/pr103798-1.c b/gcc/testsuite/c-c++-common/pr103798-1.c
> new file mode 100644
> index 00000000000..cd3edf569fc
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-1.c
> @@ -0,0 +1,28 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int
> +f (char a)
> +{
> +   return  __builtin_memchr ("a", a, 1) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> +  return a != 'a';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i) != g (i))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-2.c b/gcc/testsuite/c-c++-common/pr103798-2.c
> new file mode 100644
> index 00000000000..e7e99c3679e
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-2.c
> @@ -0,0 +1,30 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +#include <string.h>
> +
> +__attribute__ ((weak))
> +int
> +f (int a)
> +{
> +   return memchr ("aE", a, 2) != NULL;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> +  return a == 'a' || a == 'E';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i + 256) != g (i + 256))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-3.c b/gcc/testsuite/c-c++-common/pr103798-3.c
> new file mode 100644
> index 00000000000..ddcedc7e238
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-3.c
> @@ -0,0 +1,28 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int
> +f (char a)
> +{
> +   return  __builtin_memchr ("aEgZ", a, 3) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> +  return a != 'a' && a != 'E' && a != 'g';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i) != g (i))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-4.c b/gcc/testsuite/c-c++-common/pr103798-4.c
> new file mode 100644
> index 00000000000..00e8302a833
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-4.c
> @@ -0,0 +1,28 @@
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int
> +f (char a)
> +{
> +   return  __builtin_memchr ("aEgi", a, 4) != 0;
> +}
> +
> +__attribute__ ((weak))
> +int
> +g (char a)
> +{
> +  return a == 'a' || a == 'E' || a == 'g' || a == 'i';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i) != g (i))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-5.c b/gcc/testsuite/c-c++-common/pr103798-5.c
> new file mode 100644
> index 00000000000..0d6487a13df
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-5.c
> @@ -0,0 +1,26 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(char a)
> +{
> +   return  __builtin_memchr ("aEgiH", a, 5) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> +  return a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H';
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i) != g (i))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-6.c b/gcc/testsuite/c-c++-common/pr103798-6.c
> new file mode 100644
> index 00000000000..5ccb5ee66e0
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-6.c
> @@ -0,0 +1,27 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(char a)
> +{
> +   return  __builtin_memchr ("aEgiHx", a, 6) != 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> +         || a == 'x');
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i) != g (i))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-7.c b/gcc/testsuite/c-c++-common/pr103798-7.c
> new file mode 100644
> index 00000000000..40fd38257d1
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-7.c
> @@ -0,0 +1,27 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(char a)
> +{
> +   return  __builtin_memchr ("aEgiHjZ", a, 7) == 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> +  return (a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H'
> +         && a != 'j' && a != 'Z');
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i) != g (i))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/testsuite/c-c++-common/pr103798-8.c b/gcc/testsuite/c-c++-common/pr103798-8.c
> new file mode 100644
> index 00000000000..0841b18cea4
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/pr103798-8.c
> @@ -0,0 +1,27 @@
> +/* { dg-do run { target int128 } } */
> +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> +
> +__attribute__ ((weak))
> +int f(int a)
> +{
> +   return  __builtin_memchr ("aEgiHx19ABC", a, 8) != 0;
> +}
> +
> +__attribute__ ((weak))
> +int g(char a)
> +{
> +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> +         || a == 'x' || a == '1' || a == '9');
> +}
> +
> +int
> +main ()
> +{
> + for (int i = 0; i < 255; i++)
> +   if (f (i + 256) != g (i + 256))
> +     __builtin_abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-assembler-not "memchr" } } */
> diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> index 69567ab3275..edd1277c23b 100644
> --- a/gcc/tree-ssa-forwprop.cc
> +++ b/gcc/tree-ssa-forwprop.cc
> @@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "tree-dfa.h"
>  #include "tree-ssa-propagate.h"
>  #include "tree-ssa-dom.h"
> +#include "tree-ssa-strlen.h"
>  #include "builtins.h"
>  #include "tree-cfgcleanup.h"
>  #include "cfganal.h"
> @@ -1177,6 +1178,15 @@ constant_pointer_difference (tree p1, tree p2)
>     memcpy (p, "abcd   ", 7);
>     call if the latter can be stored by pieces during expansion.
>
> +   Optimize
> +   memchr ("abcd", a, 4) == 0;
> +   or
> +   memchr ("abcd", a, 4) != 0;
> +   to
> +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
> +   or
> +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') != 0
> +
>     Also canonicalize __atomic_fetch_op (p, x, y) op x
>     to __atomic_op_fetch (p, x, y) or
>     __atomic_op_fetch (p, x, y) iop x
> @@ -1193,8 +1203,62 @@ simplify_builtin_call (gimple_stmt_iterator *gsi_p, tree callee2)
>      return false;
>    stmt1 = SSA_NAME_DEF_STMT (vuse);
>
> +  tree res;
> +
>    switch (DECL_FUNCTION_CODE (callee2))
>      {
> +    case BUILT_IN_MEMCHR:
> +      if (gimple_call_num_args (stmt2) == 3
> +         && (res = gimple_call_lhs (stmt2)) != nullptr
> +         && use_in_zero_equality (res) != nullptr
> +         && CHAR_BIT == 8
> +         && BITS_PER_UNIT == 8)
> +       {
> +         tree ptr = gimple_call_arg (stmt2, 0);
> +         if (TREE_CODE (ptr) != ADDR_EXPR
> +             || TREE_CODE (TREE_OPERAND (ptr, 0)) != STRING_CST)
> +           break;
> +         unsigned HOST_WIDE_INT slen
> +           = TREE_STRING_LENGTH (TREE_OPERAND (ptr, 0));
> +         /* It must be a non-empty string constant.  */
> +         if (slen < 2)
> +           break;
> +         tree size = gimple_call_arg (stmt2, 2);
> +         /* Size must be a constant which is <= UNITS_PER_WORD and
> +            <= the string length.  */
> +         if (TREE_CODE (size) != INTEGER_CST
> +             || integer_zerop (size)
> +             || wi::gtu_p (wi::to_wide (size), UNITS_PER_WORD)
> +             || wi::geu_p (wi::to_wide (size), slen))

it might be convenient to check tree_fits_uhwi_p (size) and
do unsigned HOST_WIDE_INT sz = tree_to_uhwi (size); instead
of playing with wide-int here.

> +           break;
> +         tree ch = gimple_call_arg (stmt2, 1);
> +         location_t loc = gimple_location (stmt2);
> +         if (!useless_type_conversion_p (char_type_node,
> +                                         TREE_TYPE (ch)))
> +           ch = fold_convert_loc (loc, char_type_node, ch);
> +         const char *p = TREE_STRING_POINTER (TREE_OPERAND (ptr, 0));
> +         unsigned int isize = TREE_INT_CST_LOW (size);
> +         tree *op = new tree[isize];
> +         for (unsigned int i = 0; i < isize; i++)
> +           {
> +             op[i] = build_int_cst (char_type_node, p[i]);
> +             op[i] = fold_build2_loc (loc, EQ_EXPR, boolean_type_node,
> +                                      op[i], ch);
> +           }
> +         for (unsigned int i = isize - 1; i >= 1; i--)
> +           op[i - 1] = fold_convert_loc (loc, boolean_type_node,
> +                                         fold_build2_loc (loc,
> +                                                          BIT_IOR_EXPR,
> +                                                          boolean_type_node,
> +                                                          op[i - 1],
> +                                                          op[i]));
> +         res = fold_convert_loc (loc, TREE_TYPE (res), op[0]);
> +         gimplify_and_update_call_from_tree (gsi_p, res);

my worry about -Os remains, can you please add a check
like optimize_bb_for_speed (gimple_bb (stmt2)) || sz <= 2
(so we allow inline expanding two comparisons when not optimizing
for speed)?  For UNITS_PER_WORD == 8 this is possibly a
lot of compares, don't we have some _BY_PIECEs limit we
can use here?  There's no COMPARE_RATIO it seems,
not sure what we use there.

Since we only inline expand memchr(..) != 0 we're leaving
'a' != x | 'b' != x | ... optimization to possibly
'ab...' != (x|x<<8|x<<12|...) for followup (I'm quite sure we don't
do anything like that).  The x "splat" needs log2 (sz) operations
(but they might be slow?), but in the end it might pay off
for power-of-two (sz) (one could even do this in chunks)?
Anyway, this might be for a followup.

Otherwise it looks OK.

Thanks,
Richard.

> +         delete[] op;
> +         return true;
> +       }
> +      break;
> +
>      case BUILT_IN_MEMSET:
>        if (gimple_call_num_args (stmt2) != 3
>           || gimple_call_lhs (stmt2)
> diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
> index 7b3e3899ea2..5afbae1b72e 100644
> --- a/gcc/tree-ssa-strlen.cc
> +++ b/gcc/tree-ssa-strlen.cc
> @@ -3913,8 +3913,8 @@ strlen_pass::handle_builtin_memset (bool *zero_write)
>     nonnull if and only RES is used in such expressions exclusively and
>     in none other.  */
>
> -static gimple *
> -use_in_zero_equality (tree res, bool exclusive = true)
> +gimple *
> +use_in_zero_equality (tree res, bool exclusive)
>  {
>    gimple *first_use = NULL;
>
> diff --git a/gcc/tree-ssa-strlen.h b/gcc/tree-ssa-strlen.h
> index 8d155450db8..fdb4d9d7783 100644
> --- a/gcc/tree-ssa-strlen.h
> +++ b/gcc/tree-ssa-strlen.h
> @@ -35,6 +35,8 @@ struct c_strlen_data;
>  extern void get_range_strlen_dynamic (tree, gimple *, c_strlen_data *,
>                                       pointer_query &);
>
> +extern gimple *use_in_zero_equality (tree, bool = true);
> +
>  /* APIs internal to strlen pass.  Defined in gimple-ssa-sprintf.cc.  */
>  extern bool handle_printf_call (gimple_stmt_iterator *, pointer_query &);
>
> --
> 2.36.1
>
  

On Fri, Jul 8, 2022 at 5:54 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Thu, Jul 7, 2022 at 6:45 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > When memchr is applied on a constant string of no more than the bytes of
> > a word, simplify memchr by checking each byte in the constant string.
> >
> > int f (int a)
> > {
> >    return  __builtin_memchr ("AE", a, 2) != 0;
> > }
> >
> > is simplified to
> >
> > int f (int a)
> > {
> >   return ((char) a == 'A' || (char) a == 'E') != 0;
> > }
> >
> > gcc/
> >
> >         PR tree-optimization/103798
> >         * tree-ssa-forwprop.cc: Include "tree-ssa-strlen.h".
> >         (simplify_builtin_call): Inline memchr with constant strings of
> >         no more than the bytes of a word.
> >         * tree-ssa-strlen.cc (use_in_zero_equality): Make it global.
> >         * tree-ssa-strlen.h (use_in_zero_equality): New.
> >
> > gcc/testsuite/
> >
> >         PR tree-optimization/103798
> >         * c-c++-common/pr103798-1.c: New test.
> >         * c-c++-common/pr103798-2.c: Likewise.
> >         * c-c++-common/pr103798-3.c: Likewise.
> >         * c-c++-common/pr103798-4.c: Likewise.
> >         * c-c++-common/pr103798-5.c: Likewise.
> >         * c-c++-common/pr103798-6.c: Likewise.
> >         * c-c++-common/pr103798-7.c: Likewise.
> >         * c-c++-common/pr103798-8.c: Likewise.
> > ---
> >  gcc/testsuite/c-c++-common/pr103798-1.c | 28 +++++++++++
> >  gcc/testsuite/c-c++-common/pr103798-2.c | 30 ++++++++++++
> >  gcc/testsuite/c-c++-common/pr103798-3.c | 28 +++++++++++
> >  gcc/testsuite/c-c++-common/pr103798-4.c | 28 +++++++++++
> >  gcc/testsuite/c-c++-common/pr103798-5.c | 26 ++++++++++
> >  gcc/testsuite/c-c++-common/pr103798-6.c | 27 +++++++++++
> >  gcc/testsuite/c-c++-common/pr103798-7.c | 27 +++++++++++
> >  gcc/testsuite/c-c++-common/pr103798-8.c | 27 +++++++++++
> >  gcc/tree-ssa-forwprop.cc                | 64 +++++++++++++++++++++++++
> >  gcc/tree-ssa-strlen.cc                  |  4 +-
> >  gcc/tree-ssa-strlen.h                   |  2 +
> >  11 files changed, 289 insertions(+), 2 deletions(-)
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-1.c
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-2.c
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-3.c
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-4.c
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-5.c
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-6.c
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-7.c
> >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-8.c
> >
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-1.c b/gcc/testsuite/c-c++-common/pr103798-1.c
> > new file mode 100644
> > index 00000000000..cd3edf569fc
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-1.c
> > @@ -0,0 +1,28 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +__attribute__ ((weak))
> > +int
> > +f (char a)
> > +{
> > +   return  __builtin_memchr ("a", a, 1) == 0;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int
> > +g (char a)
> > +{
> > +  return a != 'a';
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i) != g (i))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-2.c b/gcc/testsuite/c-c++-common/pr103798-2.c
> > new file mode 100644
> > index 00000000000..e7e99c3679e
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-2.c
> > @@ -0,0 +1,30 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +#include <string.h>
> > +
> > +__attribute__ ((weak))
> > +int
> > +f (int a)
> > +{
> > +   return memchr ("aE", a, 2) != NULL;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int
> > +g (char a)
> > +{
> > +  return a == 'a' || a == 'E';
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i + 256) != g (i + 256))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-3.c b/gcc/testsuite/c-c++-common/pr103798-3.c
> > new file mode 100644
> > index 00000000000..ddcedc7e238
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-3.c
> > @@ -0,0 +1,28 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +__attribute__ ((weak))
> > +int
> > +f (char a)
> > +{
> > +   return  __builtin_memchr ("aEgZ", a, 3) == 0;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int
> > +g (char a)
> > +{
> > +  return a != 'a' && a != 'E' && a != 'g';
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i) != g (i))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-4.c b/gcc/testsuite/c-c++-common/pr103798-4.c
> > new file mode 100644
> > index 00000000000..00e8302a833
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-4.c
> > @@ -0,0 +1,28 @@
> > +/* { dg-do run } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +__attribute__ ((weak))
> > +int
> > +f (char a)
> > +{
> > +   return  __builtin_memchr ("aEgi", a, 4) != 0;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int
> > +g (char a)
> > +{
> > +  return a == 'a' || a == 'E' || a == 'g' || a == 'i';
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i) != g (i))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-5.c b/gcc/testsuite/c-c++-common/pr103798-5.c
> > new file mode 100644
> > index 00000000000..0d6487a13df
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-5.c
> > @@ -0,0 +1,26 @@
> > +/* { dg-do run { target int128 } } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +__attribute__ ((weak))
> > +int f(char a)
> > +{
> > +   return  __builtin_memchr ("aEgiH", a, 5) == 0;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int g(char a)
> > +{
> > +  return a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H';
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i) != g (i))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-6.c b/gcc/testsuite/c-c++-common/pr103798-6.c
> > new file mode 100644
> > index 00000000000..5ccb5ee66e0
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-6.c
> > @@ -0,0 +1,27 @@
> > +/* { dg-do run { target int128 } } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +__attribute__ ((weak))
> > +int f(char a)
> > +{
> > +   return  __builtin_memchr ("aEgiHx", a, 6) != 0;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int g(char a)
> > +{
> > +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> > +         || a == 'x');
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i) != g (i))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-7.c b/gcc/testsuite/c-c++-common/pr103798-7.c
> > new file mode 100644
> > index 00000000000..40fd38257d1
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-7.c
> > @@ -0,0 +1,27 @@
> > +/* { dg-do run { target int128 } } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +__attribute__ ((weak))
> > +int f(char a)
> > +{
> > +   return  __builtin_memchr ("aEgiHjZ", a, 7) == 0;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int g(char a)
> > +{
> > +  return (a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H'
> > +         && a != 'j' && a != 'Z');
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i) != g (i))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/testsuite/c-c++-common/pr103798-8.c b/gcc/testsuite/c-c++-common/pr103798-8.c
> > new file mode 100644
> > index 00000000000..0841b18cea4
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/pr103798-8.c
> > @@ -0,0 +1,27 @@
> > +/* { dg-do run { target int128 } } */
> > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > +
> > +__attribute__ ((weak))
> > +int f(int a)
> > +{
> > +   return  __builtin_memchr ("aEgiHx19ABC", a, 8) != 0;
> > +}
> > +
> > +__attribute__ ((weak))
> > +int g(char a)
> > +{
> > +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> > +         || a == 'x' || a == '1' || a == '9');
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + for (int i = 0; i < 255; i++)
> > +   if (f (i + 256) != g (i + 256))
> > +     __builtin_abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-assembler-not "memchr" } } */
> > diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> > index 69567ab3275..edd1277c23b 100644
> > --- a/gcc/tree-ssa-forwprop.cc
> > +++ b/gcc/tree-ssa-forwprop.cc
> > @@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "tree-dfa.h"
> >  #include "tree-ssa-propagate.h"
> >  #include "tree-ssa-dom.h"
> > +#include "tree-ssa-strlen.h"
> >  #include "builtins.h"
> >  #include "tree-cfgcleanup.h"
> >  #include "cfganal.h"
> > @@ -1177,6 +1178,15 @@ constant_pointer_difference (tree p1, tree p2)
> >     memcpy (p, "abcd   ", 7);
> >     call if the latter can be stored by pieces during expansion.
> >
> > +   Optimize
> > +   memchr ("abcd", a, 4) == 0;
> > +   or
> > +   memchr ("abcd", a, 4) != 0;
> > +   to
> > +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
> > +   or
> > +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') != 0
> > +
> >     Also canonicalize __atomic_fetch_op (p, x, y) op x
> >     to __atomic_op_fetch (p, x, y) or
> >     __atomic_op_fetch (p, x, y) iop x
> > @@ -1193,8 +1203,62 @@ simplify_builtin_call (gimple_stmt_iterator *gsi_p, tree callee2)
> >      return false;
> >    stmt1 = SSA_NAME_DEF_STMT (vuse);
> >
> > +  tree res;
> > +
> >    switch (DECL_FUNCTION_CODE (callee2))
> >      {
> > +    case BUILT_IN_MEMCHR:
> > +      if (gimple_call_num_args (stmt2) == 3
> > +         && (res = gimple_call_lhs (stmt2)) != nullptr
> > +         && use_in_zero_equality (res) != nullptr
> > +         && CHAR_BIT == 8
> > +         && BITS_PER_UNIT == 8)
> > +       {
> > +         tree ptr = gimple_call_arg (stmt2, 0);
> > +         if (TREE_CODE (ptr) != ADDR_EXPR
> > +             || TREE_CODE (TREE_OPERAND (ptr, 0)) != STRING_CST)
> > +           break;
> > +         unsigned HOST_WIDE_INT slen
> > +           = TREE_STRING_LENGTH (TREE_OPERAND (ptr, 0));
> > +         /* It must be a non-empty string constant.  */
> > +         if (slen < 2)
> > +           break;
> > +         tree size = gimple_call_arg (stmt2, 2);
> > +         /* Size must be a constant which is <= UNITS_PER_WORD and
> > +            <= the string length.  */
> > +         if (TREE_CODE (size) != INTEGER_CST
> > +             || integer_zerop (size)
> > +             || wi::gtu_p (wi::to_wide (size), UNITS_PER_WORD)
> > +             || wi::geu_p (wi::to_wide (size), slen))
>
> it might be convenient to check tree_fits_uhwi_p (size) and
> do unsigned HOST_WIDE_INT sz = tree_to_uhwi (size); instead
> of playing with wide-int here.

Fixed.

> > +           break;
> > +         tree ch = gimple_call_arg (stmt2, 1);
> > +         location_t loc = gimple_location (stmt2);
> > +         if (!useless_type_conversion_p (char_type_node,
> > +                                         TREE_TYPE (ch)))
> > +           ch = fold_convert_loc (loc, char_type_node, ch);
> > +         const char *p = TREE_STRING_POINTER (TREE_OPERAND (ptr, 0));
> > +         unsigned int isize = TREE_INT_CST_LOW (size);
> > +         tree *op = new tree[isize];
> > +         for (unsigned int i = 0; i < isize; i++)
> > +           {
> > +             op[i] = build_int_cst (char_type_node, p[i]);
> > +             op[i] = fold_build2_loc (loc, EQ_EXPR, boolean_type_node,
> > +                                      op[i], ch);
> > +           }
> > +         for (unsigned int i = isize - 1; i >= 1; i--)
> > +           op[i - 1] = fold_convert_loc (loc, boolean_type_node,
> > +                                         fold_build2_loc (loc,
> > +                                                          BIT_IOR_EXPR,
> > +                                                          boolean_type_node,
> > +                                                          op[i - 1],
> > +                                                          op[i]));
> > +         res = fold_convert_loc (loc, TREE_TYPE (res), op[0]);
> > +         gimplify_and_update_call_from_tree (gsi_p, res);
>
> my worry about -Os remains, can you please add a check
> like optimize_bb_for_speed (gimple_bb (stmt2)) || sz <= 2

Fixed.

> (so we allow inline expanding two comparisons when not optimizing
> for speed)?  For UNITS_PER_WORD == 8 this is possibly a
> lot of compares, don't we have some _BY_PIECEs limit we

There are a few comparisons.  Should I limit it to 4 bytes?

> can use here?  There's no COMPARE_RATIO it seems,
> not sure what we use there.
>
> Since we only inline expand memchr(..) != 0 we're leaving
> 'a' != x | 'b' != x | ... optimization to possibly

memchr("abcd", a, 4) == 0 is optimized to

(a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0

by this patch.

> 'ab...' != (x|x<<8|x<<12|...) for followup (I'm quite sure we don't

It works only for memchr("aaaa", a, 4) == 0.  It is optimized to
x != 'a' by this patch.

Thanks.

> do anything like that).  The x "splat" needs log2 (sz) operations
> (but they might be slow?), but in the end it might pay off
> for power-of-two (sz) (one could even do this in chunks)?
> Anyway, this might be for a followup.
>
> Otherwise it looks OK.
>
> Thanks,
> Richard.
>
> > +         delete[] op;
> > +         return true;
> > +       }
> > +      break;
> > +
> >      case BUILT_IN_MEMSET:
> >        if (gimple_call_num_args (stmt2) != 3
> >           || gimple_call_lhs (stmt2)
> > diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
> > index 7b3e3899ea2..5afbae1b72e 100644
> > --- a/gcc/tree-ssa-strlen.cc
> > +++ b/gcc/tree-ssa-strlen.cc
> > @@ -3913,8 +3913,8 @@ strlen_pass::handle_builtin_memset (bool *zero_write)
> >     nonnull if and only RES is used in such expressions exclusively and
> >     in none other.  */
> >
> > -static gimple *
> > -use_in_zero_equality (tree res, bool exclusive = true)
> > +gimple *
> > +use_in_zero_equality (tree res, bool exclusive)
> >  {
> >    gimple *first_use = NULL;
> >
> > diff --git a/gcc/tree-ssa-strlen.h b/gcc/tree-ssa-strlen.h
> > index 8d155450db8..fdb4d9d7783 100644
> > --- a/gcc/tree-ssa-strlen.h
> > +++ b/gcc/tree-ssa-strlen.h
> > @@ -35,6 +35,8 @@ struct c_strlen_data;
> >  extern void get_range_strlen_dynamic (tree, gimple *, c_strlen_data *,
> >                                       pointer_query &);
> >
> > +extern gimple *use_in_zero_equality (tree, bool = true);
> > +
> >  /* APIs internal to strlen pass.  Defined in gimple-ssa-sprintf.cc.  */
> >  extern bool handle_printf_call (gimple_stmt_iterator *, pointer_query &);
> >
> > --
> > 2.36.1
> >
  

On Tue, Jul 12, 2022 at 6:59 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Fri, Jul 8, 2022 at 5:54 AM Richard Biener
> <richard.guenther@gmail.com> wrote:
> >
> > On Thu, Jul 7, 2022 at 6:45 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > >
> > > When memchr is applied on a constant string of no more than the bytes of
> > > a word, simplify memchr by checking each byte in the constant string.
> > >
> > > int f (int a)
> > > {
> > >    return  __builtin_memchr ("AE", a, 2) != 0;
> > > }
> > >
> > > is simplified to
> > >
> > > int f (int a)
> > > {
> > >   return ((char) a == 'A' || (char) a == 'E') != 0;
> > > }
> > >
> > > gcc/
> > >
> > >         PR tree-optimization/103798
> > >         * tree-ssa-forwprop.cc: Include "tree-ssa-strlen.h".
> > >         (simplify_builtin_call): Inline memchr with constant strings of
> > >         no more than the bytes of a word.
> > >         * tree-ssa-strlen.cc (use_in_zero_equality): Make it global.
> > >         * tree-ssa-strlen.h (use_in_zero_equality): New.
> > >
> > > gcc/testsuite/
> > >
> > >         PR tree-optimization/103798
> > >         * c-c++-common/pr103798-1.c: New test.
> > >         * c-c++-common/pr103798-2.c: Likewise.
> > >         * c-c++-common/pr103798-3.c: Likewise.
> > >         * c-c++-common/pr103798-4.c: Likewise.
> > >         * c-c++-common/pr103798-5.c: Likewise.
> > >         * c-c++-common/pr103798-6.c: Likewise.
> > >         * c-c++-common/pr103798-7.c: Likewise.
> > >         * c-c++-common/pr103798-8.c: Likewise.
> > > ---
> > >  gcc/testsuite/c-c++-common/pr103798-1.c | 28 +++++++++++
> > >  gcc/testsuite/c-c++-common/pr103798-2.c | 30 ++++++++++++
> > >  gcc/testsuite/c-c++-common/pr103798-3.c | 28 +++++++++++
> > >  gcc/testsuite/c-c++-common/pr103798-4.c | 28 +++++++++++
> > >  gcc/testsuite/c-c++-common/pr103798-5.c | 26 ++++++++++
> > >  gcc/testsuite/c-c++-common/pr103798-6.c | 27 +++++++++++
> > >  gcc/testsuite/c-c++-common/pr103798-7.c | 27 +++++++++++
> > >  gcc/testsuite/c-c++-common/pr103798-8.c | 27 +++++++++++
> > >  gcc/tree-ssa-forwprop.cc                | 64 +++++++++++++++++++++++++
> > >  gcc/tree-ssa-strlen.cc                  |  4 +-
> > >  gcc/tree-ssa-strlen.h                   |  2 +
> > >  11 files changed, 289 insertions(+), 2 deletions(-)
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-1.c
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-2.c
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-3.c
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-4.c
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-5.c
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-6.c
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-7.c
> > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-8.c
> > >
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-1.c b/gcc/testsuite/c-c++-common/pr103798-1.c
> > > new file mode 100644
> > > index 00000000000..cd3edf569fc
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-1.c
> > > @@ -0,0 +1,28 @@
> > > +/* { dg-do run } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +f (char a)
> > > +{
> > > +   return  __builtin_memchr ("a", a, 1) == 0;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +g (char a)
> > > +{
> > > +  return a != 'a';
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i) != g (i))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-2.c b/gcc/testsuite/c-c++-common/pr103798-2.c
> > > new file mode 100644
> > > index 00000000000..e7e99c3679e
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-2.c
> > > @@ -0,0 +1,30 @@
> > > +/* { dg-do run } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +#include <string.h>
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +f (int a)
> > > +{
> > > +   return memchr ("aE", a, 2) != NULL;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +g (char a)
> > > +{
> > > +  return a == 'a' || a == 'E';
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i + 256) != g (i + 256))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-3.c b/gcc/testsuite/c-c++-common/pr103798-3.c
> > > new file mode 100644
> > > index 00000000000..ddcedc7e238
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-3.c
> > > @@ -0,0 +1,28 @@
> > > +/* { dg-do run } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +f (char a)
> > > +{
> > > +   return  __builtin_memchr ("aEgZ", a, 3) == 0;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +g (char a)
> > > +{
> > > +  return a != 'a' && a != 'E' && a != 'g';
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i) != g (i))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-4.c b/gcc/testsuite/c-c++-common/pr103798-4.c
> > > new file mode 100644
> > > index 00000000000..00e8302a833
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-4.c
> > > @@ -0,0 +1,28 @@
> > > +/* { dg-do run } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +f (char a)
> > > +{
> > > +   return  __builtin_memchr ("aEgi", a, 4) != 0;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int
> > > +g (char a)
> > > +{
> > > +  return a == 'a' || a == 'E' || a == 'g' || a == 'i';
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i) != g (i))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-5.c b/gcc/testsuite/c-c++-common/pr103798-5.c
> > > new file mode 100644
> > > index 00000000000..0d6487a13df
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-5.c
> > > @@ -0,0 +1,26 @@
> > > +/* { dg-do run { target int128 } } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +__attribute__ ((weak))
> > > +int f(char a)
> > > +{
> > > +   return  __builtin_memchr ("aEgiH", a, 5) == 0;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int g(char a)
> > > +{
> > > +  return a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H';
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i) != g (i))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-6.c b/gcc/testsuite/c-c++-common/pr103798-6.c
> > > new file mode 100644
> > > index 00000000000..5ccb5ee66e0
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-6.c
> > > @@ -0,0 +1,27 @@
> > > +/* { dg-do run { target int128 } } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +__attribute__ ((weak))
> > > +int f(char a)
> > > +{
> > > +   return  __builtin_memchr ("aEgiHx", a, 6) != 0;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int g(char a)
> > > +{
> > > +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> > > +         || a == 'x');
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i) != g (i))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-7.c b/gcc/testsuite/c-c++-common/pr103798-7.c
> > > new file mode 100644
> > > index 00000000000..40fd38257d1
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-7.c
> > > @@ -0,0 +1,27 @@
> > > +/* { dg-do run { target int128 } } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +__attribute__ ((weak))
> > > +int f(char a)
> > > +{
> > > +   return  __builtin_memchr ("aEgiHjZ", a, 7) == 0;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int g(char a)
> > > +{
> > > +  return (a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H'
> > > +         && a != 'j' && a != 'Z');
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i) != g (i))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/testsuite/c-c++-common/pr103798-8.c b/gcc/testsuite/c-c++-common/pr103798-8.c
> > > new file mode 100644
> > > index 00000000000..0841b18cea4
> > > --- /dev/null
> > > +++ b/gcc/testsuite/c-c++-common/pr103798-8.c
> > > @@ -0,0 +1,27 @@
> > > +/* { dg-do run { target int128 } } */
> > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > +
> > > +__attribute__ ((weak))
> > > +int f(int a)
> > > +{
> > > +   return  __builtin_memchr ("aEgiHx19ABC", a, 8) != 0;
> > > +}
> > > +
> > > +__attribute__ ((weak))
> > > +int g(char a)
> > > +{
> > > +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> > > +         || a == 'x' || a == '1' || a == '9');
> > > +}
> > > +
> > > +int
> > > +main ()
> > > +{
> > > + for (int i = 0; i < 255; i++)
> > > +   if (f (i + 256) != g (i + 256))
> > > +     __builtin_abort ();
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> > > index 69567ab3275..edd1277c23b 100644
> > > --- a/gcc/tree-ssa-forwprop.cc
> > > +++ b/gcc/tree-ssa-forwprop.cc
> > > @@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
> > >  #include "tree-dfa.h"
> > >  #include "tree-ssa-propagate.h"
> > >  #include "tree-ssa-dom.h"
> > > +#include "tree-ssa-strlen.h"
> > >  #include "builtins.h"
> > >  #include "tree-cfgcleanup.h"
> > >  #include "cfganal.h"
> > > @@ -1177,6 +1178,15 @@ constant_pointer_difference (tree p1, tree p2)
> > >     memcpy (p, "abcd   ", 7);
> > >     call if the latter can be stored by pieces during expansion.
> > >
> > > +   Optimize
> > > +   memchr ("abcd", a, 4) == 0;
> > > +   or
> > > +   memchr ("abcd", a, 4) != 0;
> > > +   to
> > > +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
> > > +   or
> > > +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') != 0
> > > +
> > >     Also canonicalize __atomic_fetch_op (p, x, y) op x
> > >     to __atomic_op_fetch (p, x, y) or
> > >     __atomic_op_fetch (p, x, y) iop x
> > > @@ -1193,8 +1203,62 @@ simplify_builtin_call (gimple_stmt_iterator *gsi_p, tree callee2)
> > >      return false;
> > >    stmt1 = SSA_NAME_DEF_STMT (vuse);
> > >
> > > +  tree res;
> > > +
> > >    switch (DECL_FUNCTION_CODE (callee2))
> > >      {
> > > +    case BUILT_IN_MEMCHR:
> > > +      if (gimple_call_num_args (stmt2) == 3
> > > +         && (res = gimple_call_lhs (stmt2)) != nullptr
> > > +         && use_in_zero_equality (res) != nullptr
> > > +         && CHAR_BIT == 8
> > > +         && BITS_PER_UNIT == 8)
> > > +       {
> > > +         tree ptr = gimple_call_arg (stmt2, 0);
> > > +         if (TREE_CODE (ptr) != ADDR_EXPR
> > > +             || TREE_CODE (TREE_OPERAND (ptr, 0)) != STRING_CST)
> > > +           break;
> > > +         unsigned HOST_WIDE_INT slen
> > > +           = TREE_STRING_LENGTH (TREE_OPERAND (ptr, 0));
> > > +         /* It must be a non-empty string constant.  */
> > > +         if (slen < 2)
> > > +           break;
> > > +         tree size = gimple_call_arg (stmt2, 2);
> > > +         /* Size must be a constant which is <= UNITS_PER_WORD and
> > > +            <= the string length.  */
> > > +         if (TREE_CODE (size) != INTEGER_CST
> > > +             || integer_zerop (size)
> > > +             || wi::gtu_p (wi::to_wide (size), UNITS_PER_WORD)
> > > +             || wi::geu_p (wi::to_wide (size), slen))
> >
> > it might be convenient to check tree_fits_uhwi_p (size) and
> > do unsigned HOST_WIDE_INT sz = tree_to_uhwi (size); instead
> > of playing with wide-int here.
>
> Fixed.
>
> > > +           break;
> > > +         tree ch = gimple_call_arg (stmt2, 1);
> > > +         location_t loc = gimple_location (stmt2);
> > > +         if (!useless_type_conversion_p (char_type_node,
> > > +                                         TREE_TYPE (ch)))
> > > +           ch = fold_convert_loc (loc, char_type_node, ch);
> > > +         const char *p = TREE_STRING_POINTER (TREE_OPERAND (ptr, 0));
> > > +         unsigned int isize = TREE_INT_CST_LOW (size);
> > > +         tree *op = new tree[isize];
> > > +         for (unsigned int i = 0; i < isize; i++)
> > > +           {
> > > +             op[i] = build_int_cst (char_type_node, p[i]);
> > > +             op[i] = fold_build2_loc (loc, EQ_EXPR, boolean_type_node,
> > > +                                      op[i], ch);
> > > +           }
> > > +         for (unsigned int i = isize - 1; i >= 1; i--)
> > > +           op[i - 1] = fold_convert_loc (loc, boolean_type_node,
> > > +                                         fold_build2_loc (loc,
> > > +                                                          BIT_IOR_EXPR,
> > > +                                                          boolean_type_node,
> > > +                                                          op[i - 1],
> > > +                                                          op[i]));
> > > +         res = fold_convert_loc (loc, TREE_TYPE (res), op[0]);
> > > +         gimplify_and_update_call_from_tree (gsi_p, res);
> >
> > my worry about -Os remains, can you please add a check
> > like optimize_bb_for_speed (gimple_bb (stmt2)) || sz <= 2
>
> Fixed.
>
> > (so we allow inline expanding two comparisons when not optimizing
> > for speed)?  For UNITS_PER_WORD == 8 this is possibly a
> > lot of compares, don't we have some _BY_PIECEs limit we
>
> There are a few comparisons.  Should I limit it to 4 bytes?

Not sure, if we don't have any existing target configurable limit
then using UNITS_PER_WORD is fine for now I guess.

> > can use here?  There's no COMPARE_RATIO it seems,
> > not sure what we use there.
> >
> > Since we only inline expand memchr(..) != 0 we're leaving
> > 'a' != x | 'b' != x | ... optimization to possibly
>
> memchr("abcd", a, 4) == 0 is optimized to
>
> (a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
>
> by this patch.
>
> > 'ab...' != (x|x<<8|x<<12|...) for followup (I'm quite sure we don't
>
> It works only for memchr("aaaa", a, 4) == 0.  It is optimized to
> x != 'a' by this patch.

Hmm, true ;)

Btw, no updated patch in your mail?

Thanks,
Richard.

>
> Thanks.
>
> > do anything like that).  The x "splat" needs log2 (sz) operations
> > (but they might be slow?), but in the end it might pay off
> > for power-of-two (sz) (one could even do this in chunks)?
> > Anyway, this might be for a followup.
> >
> > Otherwise it looks OK.
> >
> > Thanks,
> > Richard.
> >
> > > +         delete[] op;
> > > +         return true;
> > > +       }
> > > +      break;
> > > +
> > >      case BUILT_IN_MEMSET:
> > >        if (gimple_call_num_args (stmt2) != 3
> > >           || gimple_call_lhs (stmt2)
> > > diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
> > > index 7b3e3899ea2..5afbae1b72e 100644
> > > --- a/gcc/tree-ssa-strlen.cc
> > > +++ b/gcc/tree-ssa-strlen.cc
> > > @@ -3913,8 +3913,8 @@ strlen_pass::handle_builtin_memset (bool *zero_write)
> > >     nonnull if and only RES is used in such expressions exclusively and
> > >     in none other.  */
> > >
> > > -static gimple *
> > > -use_in_zero_equality (tree res, bool exclusive = true)
> > > +gimple *
> > > +use_in_zero_equality (tree res, bool exclusive)
> > >  {
> > >    gimple *first_use = NULL;
> > >
> > > diff --git a/gcc/tree-ssa-strlen.h b/gcc/tree-ssa-strlen.h
> > > index 8d155450db8..fdb4d9d7783 100644
> > > --- a/gcc/tree-ssa-strlen.h
> > > +++ b/gcc/tree-ssa-strlen.h
> > > @@ -35,6 +35,8 @@ struct c_strlen_data;
> > >  extern void get_range_strlen_dynamic (tree, gimple *, c_strlen_data *,
> > >                                       pointer_query &);
> > >
> > > +extern gimple *use_in_zero_equality (tree, bool = true);
> > > +
> > >  /* APIs internal to strlen pass.  Defined in gimple-ssa-sprintf.cc.  */
> > >  extern bool handle_printf_call (gimple_stmt_iterator *, pointer_query &);
> > >
> > > --
> > > 2.36.1
> > >
>
>
>
> --
> H.J.
  

On Wed, Jul 13, 2022 at 5:35 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Tue, Jul 12, 2022 at 6:59 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Fri, Jul 8, 2022 at 5:54 AM Richard Biener
> > <richard.guenther@gmail.com> wrote:
> > >
> > > On Thu, Jul 7, 2022 at 6:45 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > > >
> > > > When memchr is applied on a constant string of no more than the bytes of
> > > > a word, simplify memchr by checking each byte in the constant string.
> > > >
> > > > int f (int a)
> > > > {
> > > >    return  __builtin_memchr ("AE", a, 2) != 0;
> > > > }
> > > >
> > > > is simplified to
> > > >
> > > > int f (int a)
> > > > {
> > > >   return ((char) a == 'A' || (char) a == 'E') != 0;
> > > > }
> > > >
> > > > gcc/
> > > >
> > > >         PR tree-optimization/103798
> > > >         * tree-ssa-forwprop.cc: Include "tree-ssa-strlen.h".
> > > >         (simplify_builtin_call): Inline memchr with constant strings of
> > > >         no more than the bytes of a word.
> > > >         * tree-ssa-strlen.cc (use_in_zero_equality): Make it global.
> > > >         * tree-ssa-strlen.h (use_in_zero_equality): New.
> > > >
> > > > gcc/testsuite/
> > > >
> > > >         PR tree-optimization/103798
> > > >         * c-c++-common/pr103798-1.c: New test.
> > > >         * c-c++-common/pr103798-2.c: Likewise.
> > > >         * c-c++-common/pr103798-3.c: Likewise.
> > > >         * c-c++-common/pr103798-4.c: Likewise.
> > > >         * c-c++-common/pr103798-5.c: Likewise.
> > > >         * c-c++-common/pr103798-6.c: Likewise.
> > > >         * c-c++-common/pr103798-7.c: Likewise.
> > > >         * c-c++-common/pr103798-8.c: Likewise.
> > > > ---
> > > >  gcc/testsuite/c-c++-common/pr103798-1.c | 28 +++++++++++
> > > >  gcc/testsuite/c-c++-common/pr103798-2.c | 30 ++++++++++++
> > > >  gcc/testsuite/c-c++-common/pr103798-3.c | 28 +++++++++++
> > > >  gcc/testsuite/c-c++-common/pr103798-4.c | 28 +++++++++++
> > > >  gcc/testsuite/c-c++-common/pr103798-5.c | 26 ++++++++++
> > > >  gcc/testsuite/c-c++-common/pr103798-6.c | 27 +++++++++++
> > > >  gcc/testsuite/c-c++-common/pr103798-7.c | 27 +++++++++++
> > > >  gcc/testsuite/c-c++-common/pr103798-8.c | 27 +++++++++++
> > > >  gcc/tree-ssa-forwprop.cc                | 64 +++++++++++++++++++++++++
> > > >  gcc/tree-ssa-strlen.cc                  |  4 +-
> > > >  gcc/tree-ssa-strlen.h                   |  2 +
> > > >  11 files changed, 289 insertions(+), 2 deletions(-)
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-1.c
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-2.c
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-3.c
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-4.c
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-5.c
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-6.c
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-7.c
> > > >  create mode 100644 gcc/testsuite/c-c++-common/pr103798-8.c
> > > >
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-1.c b/gcc/testsuite/c-c++-common/pr103798-1.c
> > > > new file mode 100644
> > > > index 00000000000..cd3edf569fc
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-1.c
> > > > @@ -0,0 +1,28 @@
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +f (char a)
> > > > +{
> > > > +   return  __builtin_memchr ("a", a, 1) == 0;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +g (char a)
> > > > +{
> > > > +  return a != 'a';
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i) != g (i))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-2.c b/gcc/testsuite/c-c++-common/pr103798-2.c
> > > > new file mode 100644
> > > > index 00000000000..e7e99c3679e
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-2.c
> > > > @@ -0,0 +1,30 @@
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +#include <string.h>
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +f (int a)
> > > > +{
> > > > +   return memchr ("aE", a, 2) != NULL;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +g (char a)
> > > > +{
> > > > +  return a == 'a' || a == 'E';
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i + 256) != g (i + 256))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-3.c b/gcc/testsuite/c-c++-common/pr103798-3.c
> > > > new file mode 100644
> > > > index 00000000000..ddcedc7e238
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-3.c
> > > > @@ -0,0 +1,28 @@
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +f (char a)
> > > > +{
> > > > +   return  __builtin_memchr ("aEgZ", a, 3) == 0;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +g (char a)
> > > > +{
> > > > +  return a != 'a' && a != 'E' && a != 'g';
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i) != g (i))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-4.c b/gcc/testsuite/c-c++-common/pr103798-4.c
> > > > new file mode 100644
> > > > index 00000000000..00e8302a833
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-4.c
> > > > @@ -0,0 +1,28 @@
> > > > +/* { dg-do run } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +f (char a)
> > > > +{
> > > > +   return  __builtin_memchr ("aEgi", a, 4) != 0;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int
> > > > +g (char a)
> > > > +{
> > > > +  return a == 'a' || a == 'E' || a == 'g' || a == 'i';
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i) != g (i))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-5.c b/gcc/testsuite/c-c++-common/pr103798-5.c
> > > > new file mode 100644
> > > > index 00000000000..0d6487a13df
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-5.c
> > > > @@ -0,0 +1,26 @@
> > > > +/* { dg-do run { target int128 } } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int f(char a)
> > > > +{
> > > > +   return  __builtin_memchr ("aEgiH", a, 5) == 0;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int g(char a)
> > > > +{
> > > > +  return a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H';
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i) != g (i))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-6.c b/gcc/testsuite/c-c++-common/pr103798-6.c
> > > > new file mode 100644
> > > > index 00000000000..5ccb5ee66e0
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-6.c
> > > > @@ -0,0 +1,27 @@
> > > > +/* { dg-do run { target int128 } } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int f(char a)
> > > > +{
> > > > +   return  __builtin_memchr ("aEgiHx", a, 6) != 0;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int g(char a)
> > > > +{
> > > > +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> > > > +         || a == 'x');
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i) != g (i))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-7.c b/gcc/testsuite/c-c++-common/pr103798-7.c
> > > > new file mode 100644
> > > > index 00000000000..40fd38257d1
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-7.c
> > > > @@ -0,0 +1,27 @@
> > > > +/* { dg-do run { target int128 } } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int f(char a)
> > > > +{
> > > > +   return  __builtin_memchr ("aEgiHjZ", a, 7) == 0;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int g(char a)
> > > > +{
> > > > +  return (a != 'a' && a != 'E' && a != 'g' && a != 'i' && a != 'H'
> > > > +         && a != 'j' && a != 'Z');
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i) != g (i))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/testsuite/c-c++-common/pr103798-8.c b/gcc/testsuite/c-c++-common/pr103798-8.c
> > > > new file mode 100644
> > > > index 00000000000..0841b18cea4
> > > > --- /dev/null
> > > > +++ b/gcc/testsuite/c-c++-common/pr103798-8.c
> > > > @@ -0,0 +1,27 @@
> > > > +/* { dg-do run { target int128 } } */
> > > > +/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int f(int a)
> > > > +{
> > > > +   return  __builtin_memchr ("aEgiHx19ABC", a, 8) != 0;
> > > > +}
> > > > +
> > > > +__attribute__ ((weak))
> > > > +int g(char a)
> > > > +{
> > > > +  return (a == 'a' || a == 'E' || a == 'g' || a == 'i' || a == 'H'
> > > > +         || a == 'x' || a == '1' || a == '9');
> > > > +}
> > > > +
> > > > +int
> > > > +main ()
> > > > +{
> > > > + for (int i = 0; i < 255; i++)
> > > > +   if (f (i + 256) != g (i + 256))
> > > > +     __builtin_abort ();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +/* { dg-final { scan-assembler-not "memchr" } } */
> > > > diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> > > > index 69567ab3275..edd1277c23b 100644
> > > > --- a/gcc/tree-ssa-forwprop.cc
> > > > +++ b/gcc/tree-ssa-forwprop.cc
> > > > @@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
> > > >  #include "tree-dfa.h"
> > > >  #include "tree-ssa-propagate.h"
> > > >  #include "tree-ssa-dom.h"
> > > > +#include "tree-ssa-strlen.h"
> > > >  #include "builtins.h"
> > > >  #include "tree-cfgcleanup.h"
> > > >  #include "cfganal.h"
> > > > @@ -1177,6 +1178,15 @@ constant_pointer_difference (tree p1, tree p2)
> > > >     memcpy (p, "abcd   ", 7);
> > > >     call if the latter can be stored by pieces during expansion.
> > > >
> > > > +   Optimize
> > > > +   memchr ("abcd", a, 4) == 0;
> > > > +   or
> > > > +   memchr ("abcd", a, 4) != 0;
> > > > +   to
> > > > +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
> > > > +   or
> > > > +   (a == 'a' || a == 'b' || a == 'c' || a == 'd') != 0
> > > > +
> > > >     Also canonicalize __atomic_fetch_op (p, x, y) op x
> > > >     to __atomic_op_fetch (p, x, y) or
> > > >     __atomic_op_fetch (p, x, y) iop x
> > > > @@ -1193,8 +1203,62 @@ simplify_builtin_call (gimple_stmt_iterator *gsi_p, tree callee2)
> > > >      return false;
> > > >    stmt1 = SSA_NAME_DEF_STMT (vuse);
> > > >
> > > > +  tree res;
> > > > +
> > > >    switch (DECL_FUNCTION_CODE (callee2))
> > > >      {
> > > > +    case BUILT_IN_MEMCHR:
> > > > +      if (gimple_call_num_args (stmt2) == 3
> > > > +         && (res = gimple_call_lhs (stmt2)) != nullptr
> > > > +         && use_in_zero_equality (res) != nullptr
> > > > +         && CHAR_BIT == 8
> > > > +         && BITS_PER_UNIT == 8)
> > > > +       {
> > > > +         tree ptr = gimple_call_arg (stmt2, 0);
> > > > +         if (TREE_CODE (ptr) != ADDR_EXPR
> > > > +             || TREE_CODE (TREE_OPERAND (ptr, 0)) != STRING_CST)
> > > > +           break;
> > > > +         unsigned HOST_WIDE_INT slen
> > > > +           = TREE_STRING_LENGTH (TREE_OPERAND (ptr, 0));
> > > > +         /* It must be a non-empty string constant.  */
> > > > +         if (slen < 2)
> > > > +           break;
> > > > +         tree size = gimple_call_arg (stmt2, 2);
> > > > +         /* Size must be a constant which is <= UNITS_PER_WORD and
> > > > +            <= the string length.  */
> > > > +         if (TREE_CODE (size) != INTEGER_CST
> > > > +             || integer_zerop (size)
> > > > +             || wi::gtu_p (wi::to_wide (size), UNITS_PER_WORD)
> > > > +             || wi::geu_p (wi::to_wide (size), slen))
> > >
> > > it might be convenient to check tree_fits_uhwi_p (size) and
> > > do unsigned HOST_WIDE_INT sz = tree_to_uhwi (size); instead
> > > of playing with wide-int here.
> >
> > Fixed.
> >
> > > > +           break;
> > > > +         tree ch = gimple_call_arg (stmt2, 1);
> > > > +         location_t loc = gimple_location (stmt2);
> > > > +         if (!useless_type_conversion_p (char_type_node,
> > > > +                                         TREE_TYPE (ch)))
> > > > +           ch = fold_convert_loc (loc, char_type_node, ch);
> > > > +         const char *p = TREE_STRING_POINTER (TREE_OPERAND (ptr, 0));
> > > > +         unsigned int isize = TREE_INT_CST_LOW (size);
> > > > +         tree *op = new tree[isize];
> > > > +         for (unsigned int i = 0; i < isize; i++)
> > > > +           {
> > > > +             op[i] = build_int_cst (char_type_node, p[i]);
> > > > +             op[i] = fold_build2_loc (loc, EQ_EXPR, boolean_type_node,
> > > > +                                      op[i], ch);
> > > > +           }
> > > > +         for (unsigned int i = isize - 1; i >= 1; i--)
> > > > +           op[i - 1] = fold_convert_loc (loc, boolean_type_node,
> > > > +                                         fold_build2_loc (loc,
> > > > +                                                          BIT_IOR_EXPR,
> > > > +                                                          boolean_type_node,
> > > > +                                                          op[i - 1],
> > > > +                                                          op[i]));
> > > > +         res = fold_convert_loc (loc, TREE_TYPE (res), op[0]);
> > > > +         gimplify_and_update_call_from_tree (gsi_p, res);
> > >
> > > my worry about -Os remains, can you please add a check
> > > like optimize_bb_for_speed (gimple_bb (stmt2)) || sz <= 2
> >
> > Fixed.
> >
> > > (so we allow inline expanding two comparisons when not optimizing
> > > for speed)?  For UNITS_PER_WORD == 8 this is possibly a
> > > lot of compares, don't we have some _BY_PIECEs limit we
> >
> > There are a few comparisons.  Should I limit it to 4 bytes?
>
> Not sure, if we don't have any existing target configurable limit
> then using UNITS_PER_WORD is fine for now I guess.
>
> > > can use here?  There's no COMPARE_RATIO it seems,
> > > not sure what we use there.
> > >
> > > Since we only inline expand memchr(..) != 0 we're leaving
> > > 'a' != x | 'b' != x | ... optimization to possibly
> >
> > memchr("abcd", a, 4) == 0 is optimized to
> >
> > (a == 'a' || a == 'b' || a == 'c' || a == 'd') == 0
> >
> > by this patch.
> >
> > > 'ab...' != (x|x<<8|x<<12|...) for followup (I'm quite sure we don't
> >
> > It works only for memchr("aaaa", a, 4) == 0.  It is optimized to
> > x != 'a' by this patch.
>
> Hmm, true ;)
>
> Btw, no updated patch in your mail?

Here is the v3 patch:

https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598362.html

Thanks.

> Thanks
> Richard.
>
> >
> > Thanks.
> >
> > > do anything like that).  The x "splat" needs log2 (sz) operations
> > > (but they might be slow?), but in the end it might pay off
> > > for power-of-two (sz) (one could even do this in chunks)?
> > > Anyway, this might be for a followup.
> > >
> > > Otherwise it looks OK.
> > >
> > > Thanks,
> > > Richard.
> > >
> > > > +         delete[] op;
> > > > +         return true;
> > > > +       }
> > > > +      break;
> > > > +
> > > >      case BUILT_IN_MEMSET:
> > > >        if (gimple_call_num_args (stmt2) != 3
> > > >           || gimple_call_lhs (stmt2)
> > > > diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
> > > > index 7b3e3899ea2..5afbae1b72e 100644
> > > > --- a/gcc/tree-ssa-strlen.cc
> > > > +++ b/gcc/tree-ssa-strlen.cc
> > > > @@ -3913,8 +3913,8 @@ strlen_pass::handle_builtin_memset (bool *zero_write)
> > > >     nonnull if and only RES is used in such expressions exclusively and
> > > >     in none other.  */
> > > >
> > > > -static gimple *
> > > > -use_in_zero_equality (tree res, bool exclusive = true)
> > > > +gimple *
> > > > +use_in_zero_equality (tree res, bool exclusive)
> > > >  {
> > > >    gimple *first_use = NULL;
> > > >
> > > > diff --git a/gcc/tree-ssa-strlen.h b/gcc/tree-ssa-strlen.h
> > > > index 8d155450db8..fdb4d9d7783 100644
> > > > --- a/gcc/tree-ssa-strlen.h
> > > > +++ b/gcc/tree-ssa-strlen.h
> > > > @@ -35,6 +35,8 @@ struct c_strlen_data;
> > > >  extern void get_range_strlen_dynamic (tree, gimple *, c_strlen_data *,
> > > >                                       pointer_query &);
> > > >
> > > > +extern gimple *use_in_zero_equality (tree, bool = true);
> > > > +
> > > >  /* APIs internal to strlen pass.  Defined in gimple-ssa-sprintf.cc.  */
> > > >  extern bool handle_printf_call (gimple_stmt_iterator *, pointer_query &);
> > > >
> > > > --
> > > > 2.36.1
> > > >
> >
> >
> >
> > --
> > H.J.