Add -fextra-libc-function=memcmpeq for __memcmpeq

Add -fextra-libc-function=memcmpeq to map

extern int __memcmpeq (const void *, const void *, size_t);

which was added to GLIBC 2.35, to __builtin_memcmp_eq.

gcc/

	* builtins.cc: Include "opts.h".
	(expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
	available.
	* builtins.def (BUILT_IN___MEMCMPEQ): New.
	* common.opt: Add -fextra-libc-function=.
	* opts.cc (extra_libc_functions): New.
	(parse_extra_libc_function): New function.
	(common_handle_option): Handle -fextra-libc-function=.
	* opts.h (extra_libc_function_list): New.
	(extra_libc_functions): Likewise.
	* doc/invoke.texi: Document -fextra-libc-function=memcmpeq.

gcc/testsuite/

	* c-c++-common/memcmpeq-1.c: New test.
	* c-c++-common/memcmpeq-2.c: Likewise.
	* c-c++-common/memcmpeq-3.c: Likewise.
	* c-c++-common/memcmpeq-4.c: Likewise.
	* c-c++-common/memcmpeq-5.c: Likewise.
	* c-c++-common/memcmpeq-6.c: Likewise.
	* c-c++-common/memcmpeq-7.c: Likewise.
---
 gcc/builtins.cc                         |  5 ++++-
 gcc/builtins.def                        |  4 ++++
 gcc/common.opt                          |  4 ++++
 gcc/doc/invoke.texi                     |  6 ++++++
 gcc/opts.cc                             | 23 +++++++++++++++++++++++
 gcc/opts.h                              |  7 +++++++
 gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
 gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
 13 files changed, 125 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
 create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c

On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Add -fextra-libc-function=memcmpeq to map
>
> extern int __memcmpeq (const void *, const void *, size_t);
>
> which was added to GLIBC 2.35, to __builtin_memcmp_eq.

Humm.  Can't we instead use the presence of a declaration
of __memcmpeq with a GNU standard dialect as this instead of
adding a weird -fextra-libc-function= option?  Maybe that's even
reasonable with a non-GNU dialect standard in effect since
__ prefixed names are in the implementation namespace?

Richard.

> gcc/
>
>         * builtins.cc: Include "opts.h".
>         (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
>         available.
>         * builtins.def (BUILT_IN___MEMCMPEQ): New.
>         * common.opt: Add -fextra-libc-function=.
>         * opts.cc (extra_libc_functions): New.
>         (parse_extra_libc_function): New function.
>         (common_handle_option): Handle -fextra-libc-function=.
>         * opts.h (extra_libc_function_list): New.
>         (extra_libc_functions): Likewise.
>         * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
>
> gcc/testsuite/
>
>         * c-c++-common/memcmpeq-1.c: New test.
>         * c-c++-common/memcmpeq-2.c: Likewise.
>         * c-c++-common/memcmpeq-3.c: Likewise.
>         * c-c++-common/memcmpeq-4.c: Likewise.
>         * c-c++-common/memcmpeq-5.c: Likewise.
>         * c-c++-common/memcmpeq-6.c: Likewise.
>         * c-c++-common/memcmpeq-7.c: Likewise.
> ---
>  gcc/builtins.cc                         |  5 ++++-
>  gcc/builtins.def                        |  4 ++++
>  gcc/common.opt                          |  4 ++++
>  gcc/doc/invoke.texi                     |  6 ++++++
>  gcc/opts.cc                             | 23 +++++++++++++++++++++++
>  gcc/opts.h                              |  7 +++++++
>  gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
>  13 files changed, 125 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
>  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
>
> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> index b9d89b409b8..22269318e8c 100644
> --- a/gcc/builtins.cc
> +++ b/gcc/builtins.cc
> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "demangle.h"
>  #include "gimple-range.h"
>  #include "pointer-query.h"
> +#include "opts.h"
>
>  struct target_builtins default_target_builtins;
>  #if SWITCHABLE_TARGET
> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
>         return target;
>        if (fcode == BUILT_IN_MEMCMP_EQ)
>         {
> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> +         tree newdecl = builtin_decl_explicit
> +           (extra_libc_functions.has_memcmpeq
> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
>           TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
>         }
>        break;
> diff --git a/gcc/builtins.def b/gcc/builtins.def
> index 005976f34e9..eb8d33b16e9 100644
> --- a/gcc/builtins.def
> +++ b/gcc/builtins.def
> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
>     equality with zero.  */
>  DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
>
> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> +   -fextra-libc-function=memcmpeq.  */
> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> +
>  /* An internal version of strcmp/strncmp, used when the result is only
>     tested for equality with zero.  */
>  DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 7ca0cceed82..7a7631682b0 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
>  EnumValue
>  Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
>
> +fextra-libc-function=
> +Common Driver Joined
> +Specify the extra function in the C library.
> +
>  ; Whether we permit the extended set of values for FLT_EVAL_METHOD
>  ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
>  fpermitted-flt-eval-methods=
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 8cd5bdddc5d..fe1e3709953 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
>  -ffixed-@var{reg}  -fexceptions @gol
>  -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
>  -fasynchronous-unwind-tables @gol
> +-fextra-libc-function=memcmpeq @gol
>  -fno-gnu-unique @gol
>  -finhibit-size-directive  -fcommon  -fno-ident @gol
>  -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
>  table is exact at each instruction boundary, so it can be used for stack
>  unwinding from asynchronous events (such as debugger or garbage collector).
>
> +@item -fextra-libc-function=memcmpeq
> +@opindex fextra-libc-function
> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> +@code{__builtin_memcmp_eq}.
> +
>  @item -fno-gnu-unique
>  @opindex fno-gnu-unique
>  @opindex fgnu-unique
> diff --git a/gcc/opts.cc b/gcc/opts.cc
> index bf06a55456a..e77f0922acc 100644
> --- a/gcc/opts.cc
> +++ b/gcc/opts.cc
> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
>  /* In this file all option sets are explicit.  */
>  #undef OPTION_SET_P
>
> +/* The list of extra functions in the C library.  */
> +extra_libc_function_list extra_libc_functions;
> +
>  static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
>
>  /* Names of fundamental debug info formats indexed by enum
> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
>    return flags;
>  }
>
> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> +
> +static void
> +parse_extra_libc_function (const char *arg)
> +{
> +  /* Check to see if the string matches a sub-option name.  */
> +  if (strcmp (arg, "memcmpeq") == 0)
> +    {
> +      extra_libc_functions.has_memcmpeq = 1;
> +      return;
> +    }
> +
> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> +        arg);
> +}
> +
>  /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
>
>  unsigned int
> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
>        SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
>        break;
>
> +    case OPT_fextra_libc_function_:
> +      parse_extra_libc_function (arg);
> +      break;
> +
>      case OPT_fprofile_generate_:
>        opts->x_profile_data_prefix = xstrdup (arg);
>        value = true;
> diff --git a/gcc/opts.h b/gcc/opts.h
> index a43ce66cffe..e8d8835ba23 100644
> --- a/gcc/opts.h
> +++ b/gcc/opts.h
> @@ -345,6 +345,13 @@ struct cl_option_handlers
>  extern const char *opt_fstack_limit_symbol_arg;
>  extern int opt_fstack_limit_register_no;
>
> +/* The list of extra functions in the C library.  */
> +struct extra_libc_function_list
> +{
> +  unsigned int has_memcmpeq : 1;
> +};
> +extern extra_libc_function_list extra_libc_functions;
> +
>  /* Input file names.  */
>
>  extern const char **in_fnames;
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> new file mode 100644
> index 00000000000..487f6cd98db
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp (s1, s2, len) != 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> new file mode 100644
> index 00000000000..1773dc2bee1
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include <string.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return memcmp (s1, s2, len) == 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> new file mode 100644
> index 00000000000..69c9537d572
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <string.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return memcmp (s1, s2, len);
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> new file mode 100644
> index 00000000000..a448312ea96
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp (s1, s2, len) != 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> new file mode 100644
> index 00000000000..4ef33a1c238
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <string.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return memcmp (s1, s2, len) == 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> new file mode 100644
> index 00000000000..52304df7079
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> new file mode 100644
> index 00000000000..d59765894e7
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> +}
> --
> 2.36.1
>

On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Add -fextra-libc-function=memcmpeq to map
> >
> > extern int __memcmpeq (const void *, const void *, size_t);
> >
> > which was added to GLIBC 2.35, to __builtin_memcmp_eq.
>
> Humm.  Can't we instead use the presence of a declaration
> of __memcmpeq with a GNU standard dialect as this instead of
> adding a weird -fextra-libc-function= option?  Maybe that's even
> reasonable with a non-GNU dialect standard in effect since
> __ prefixed names are in the implementation namespace?

But not all source codes include <string.h> and GCC may generate
memcmp directly.  How should we handle these cases?

> Richard.
>
> > gcc/
> >
> >         * builtins.cc: Include "opts.h".
> >         (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> >         available.
> >         * builtins.def (BUILT_IN___MEMCMPEQ): New.
> >         * common.opt: Add -fextra-libc-function=.
> >         * opts.cc (extra_libc_functions): New.
> >         (parse_extra_libc_function): New function.
> >         (common_handle_option): Handle -fextra-libc-function=.
> >         * opts.h (extra_libc_function_list): New.
> >         (extra_libc_functions): Likewise.
> >         * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> >
> > gcc/testsuite/
> >
> >         * c-c++-common/memcmpeq-1.c: New test.
> >         * c-c++-common/memcmpeq-2.c: Likewise.
> >         * c-c++-common/memcmpeq-3.c: Likewise.
> >         * c-c++-common/memcmpeq-4.c: Likewise.
> >         * c-c++-common/memcmpeq-5.c: Likewise.
> >         * c-c++-common/memcmpeq-6.c: Likewise.
> >         * c-c++-common/memcmpeq-7.c: Likewise.
> > ---
> >  gcc/builtins.cc                         |  5 ++++-
> >  gcc/builtins.def                        |  4 ++++
> >  gcc/common.opt                          |  4 ++++
> >  gcc/doc/invoke.texi                     |  6 ++++++
> >  gcc/opts.cc                             | 23 +++++++++++++++++++++++
> >  gcc/opts.h                              |  7 +++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> >  gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> >  13 files changed, 125 insertions(+), 1 deletion(-)
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> >  create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> >
> > diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> > index b9d89b409b8..22269318e8c 100644
> > --- a/gcc/builtins.cc
> > +++ b/gcc/builtins.cc
> > @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "demangle.h"
> >  #include "gimple-range.h"
> >  #include "pointer-query.h"
> > +#include "opts.h"
> >
> >  struct target_builtins default_target_builtins;
> >  #if SWITCHABLE_TARGET
> > @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> >         return target;
> >        if (fcode == BUILT_IN_MEMCMP_EQ)
> >         {
> > -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> > +         tree newdecl = builtin_decl_explicit
> > +           (extra_libc_functions.has_memcmpeq
> > +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> >           TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> >         }
> >        break;
> > diff --git a/gcc/builtins.def b/gcc/builtins.def
> > index 005976f34e9..eb8d33b16e9 100644
> > --- a/gcc/builtins.def
> > +++ b/gcc/builtins.def
> > @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> >     equality with zero.  */
> >  DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> >
> > +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> > +   -fextra-libc-function=memcmpeq.  */
> > +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> > +
> >  /* An internal version of strcmp/strncmp, used when the result is only
> >     tested for equality with zero.  */
> >  DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> > diff --git a/gcc/common.opt b/gcc/common.opt
> > index 7ca0cceed82..7a7631682b0 100644
> > --- a/gcc/common.opt
> > +++ b/gcc/common.opt
> > @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> >  EnumValue
> >  Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> >
> > +fextra-libc-function=
> > +Common Driver Joined
> > +Specify the extra function in the C library.
> > +
> >  ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> >  ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> >  fpermitted-flt-eval-methods=
> > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > index 8cd5bdddc5d..fe1e3709953 100644
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> >  -ffixed-@var{reg}  -fexceptions @gol
> >  -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> >  -fasynchronous-unwind-tables @gol
> > +-fextra-libc-function=memcmpeq @gol
> >  -fno-gnu-unique @gol
> >  -finhibit-size-directive  -fcommon  -fno-ident @gol
> >  -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> > @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> >  table is exact at each instruction boundary, so it can be used for stack
> >  unwinding from asynchronous events (such as debugger or garbage collector).
> >
> > +@item -fextra-libc-function=memcmpeq
> > +@opindex fextra-libc-function
> > +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> > +@code{__builtin_memcmp_eq}.
> > +
> >  @item -fno-gnu-unique
> >  @opindex fno-gnu-unique
> >  @opindex fgnu-unique
> > diff --git a/gcc/opts.cc b/gcc/opts.cc
> > index bf06a55456a..e77f0922acc 100644
> > --- a/gcc/opts.cc
> > +++ b/gcc/opts.cc
> > @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> >  /* In this file all option sets are explicit.  */
> >  #undef OPTION_SET_P
> >
> > +/* The list of extra functions in the C library.  */
> > +extra_libc_function_list extra_libc_functions;
> > +
> >  static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> >
> >  /* Names of fundamental debug info formats indexed by enum
> > @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> >    return flags;
> >  }
> >
> > +/* Parse -fextra-libc-function= suboptions from ARG.  */
> > +
> > +static void
> > +parse_extra_libc_function (const char *arg)
> > +{
> > +  /* Check to see if the string matches a sub-option name.  */
> > +  if (strcmp (arg, "memcmpeq") == 0)
> > +    {
> > +      extra_libc_functions.has_memcmpeq = 1;
> > +      return;
> > +    }
> > +
> > +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> > +        arg);
> > +}
> > +
> >  /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> >
> >  unsigned int
> > @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> >        SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> >        break;
> >
> > +    case OPT_fextra_libc_function_:
> > +      parse_extra_libc_function (arg);
> > +      break;
> > +
> >      case OPT_fprofile_generate_:
> >        opts->x_profile_data_prefix = xstrdup (arg);
> >        value = true;
> > diff --git a/gcc/opts.h b/gcc/opts.h
> > index a43ce66cffe..e8d8835ba23 100644
> > --- a/gcc/opts.h
> > +++ b/gcc/opts.h
> > @@ -345,6 +345,13 @@ struct cl_option_handlers
> >  extern const char *opt_fstack_limit_symbol_arg;
> >  extern int opt_fstack_limit_register_no;
> >
> > +/* The list of extra functions in the C library.  */
> > +struct extra_libc_function_list
> > +{
> > +  unsigned int has_memcmpeq : 1;
> > +};
> > +extern extra_libc_function_list extra_libc_functions;
> > +
> >  /* Input file names.  */
> >
> >  extern const char **in_fnames;
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > new file mode 100644
> > index 00000000000..487f6cd98db
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp (s1, s2, len) != 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > new file mode 100644
> > index 00000000000..1773dc2bee1
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > +
> > +#include <string.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return memcmp (s1, s2, len) == 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > new file mode 100644
> > index 00000000000..69c9537d572
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <string.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return memcmp (s1, s2, len);
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > new file mode 100644
> > index 00000000000..a448312ea96
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp (s1, s2, len) != 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > new file mode 100644
> > index 00000000000..4ef33a1c238
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <string.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return memcmp (s1, s2, len) == 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > new file mode 100644
> > index 00000000000..52304df7079
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > +}
> > diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > new file mode 100644
> > index 00000000000..d59765894e7
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > +
> > +#include <stddef.h>
> > +
> > +int
> > +foo (const char *s1, const char *s2, size_t len)
> > +{
> > +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > +}
> > --
> > 2.36.1
> >

> Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> 
> On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> <richard.guenther@gmail.com> wrote:
>> 
>>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
>>> <gcc-patches@gcc.gnu.org> wrote:
>>> 
>>> Add -fextra-libc-function=memcmpeq to map
>>> 
>>> extern int __memcmpeq (const void *, const void *, size_t);
>>> 
>>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
>> 
>> Humm.  Can't we instead use the presence of a declaration
>> of __memcmpeq with a GNU standard dialect as this instead of
>> adding a weird -fextra-libc-function= option?  Maybe that's even
>> reasonable with a non-GNU dialect standard in effect since
>> __ prefixed names are in the implementation namespace?
> 
> But not all source codes include <string.h> and GCC may generate
> memcmp directly.  How should we handle these cases?

Not.  Similar as to vectorized math functions.
I think it’s not worth optimizing for this case.

Richard.

> 
>> Richard.
>> 
>>> gcc/
>>> 
>>>        * builtins.cc: Include "opts.h".
>>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
>>>        available.
>>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
>>>        * common.opt: Add -fextra-libc-function=.
>>>        * opts.cc (extra_libc_functions): New.
>>>        (parse_extra_libc_function): New function.
>>>        (common_handle_option): Handle -fextra-libc-function=.
>>>        * opts.h (extra_libc_function_list): New.
>>>        (extra_libc_functions): Likewise.
>>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
>>> 
>>> gcc/testsuite/
>>> 
>>>        * c-c++-common/memcmpeq-1.c: New test.
>>>        * c-c++-common/memcmpeq-2.c: Likewise.
>>>        * c-c++-common/memcmpeq-3.c: Likewise.
>>>        * c-c++-common/memcmpeq-4.c: Likewise.
>>>        * c-c++-common/memcmpeq-5.c: Likewise.
>>>        * c-c++-common/memcmpeq-6.c: Likewise.
>>>        * c-c++-common/memcmpeq-7.c: Likewise.
>>> ---
>>> gcc/builtins.cc                         |  5 ++++-
>>> gcc/builtins.def                        |  4 ++++
>>> gcc/common.opt                          |  4 ++++
>>> gcc/doc/invoke.texi                     |  6 ++++++
>>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
>>> gcc/opts.h                              |  7 +++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
>>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
>>> 13 files changed, 125 insertions(+), 1 deletion(-)
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
>>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
>>> 
>>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
>>> index b9d89b409b8..22269318e8c 100644
>>> --- a/gcc/builtins.cc
>>> +++ b/gcc/builtins.cc
>>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
>>> #include "demangle.h"
>>> #include "gimple-range.h"
>>> #include "pointer-query.h"
>>> +#include "opts.h"
>>> 
>>> struct target_builtins default_target_builtins;
>>> #if SWITCHABLE_TARGET
>>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
>>>        return target;
>>>       if (fcode == BUILT_IN_MEMCMP_EQ)
>>>        {
>>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
>>> +         tree newdecl = builtin_decl_explicit
>>> +           (extra_libc_functions.has_memcmpeq
>>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
>>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
>>>        }
>>>       break;
>>> diff --git a/gcc/builtins.def b/gcc/builtins.def
>>> index 005976f34e9..eb8d33b16e9 100644
>>> --- a/gcc/builtins.def
>>> +++ b/gcc/builtins.def
>>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
>>>    equality with zero.  */
>>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
>>> 
>>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
>>> +   -fextra-libc-function=memcmpeq.  */
>>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
>>> +
>>> /* An internal version of strcmp/strncmp, used when the result is only
>>>    tested for equality with zero.  */
>>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
>>> diff --git a/gcc/common.opt b/gcc/common.opt
>>> index 7ca0cceed82..7a7631682b0 100644
>>> --- a/gcc/common.opt
>>> +++ b/gcc/common.opt
>>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
>>> EnumValue
>>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
>>> 
>>> +fextra-libc-function=
>>> +Common Driver Joined
>>> +Specify the extra function in the C library.
>>> +
>>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
>>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
>>> fpermitted-flt-eval-methods=
>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>> index 8cd5bdddc5d..fe1e3709953 100644
>>> --- a/gcc/doc/invoke.texi
>>> +++ b/gcc/doc/invoke.texi
>>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
>>> -ffixed-@var{reg}  -fexceptions @gol
>>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
>>> -fasynchronous-unwind-tables @gol
>>> +-fextra-libc-function=memcmpeq @gol
>>> -fno-gnu-unique @gol
>>> -finhibit-size-directive  -fcommon  -fno-ident @gol
>>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
>>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
>>> table is exact at each instruction boundary, so it can be used for stack
>>> unwinding from asynchronous events (such as debugger or garbage collector).
>>> 
>>> +@item -fextra-libc-function=memcmpeq
>>> +@opindex fextra-libc-function
>>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
>>> +@code{__builtin_memcmp_eq}.
>>> +
>>> @item -fno-gnu-unique
>>> @opindex fno-gnu-unique
>>> @opindex fgnu-unique
>>> diff --git a/gcc/opts.cc b/gcc/opts.cc
>>> index bf06a55456a..e77f0922acc 100644
>>> --- a/gcc/opts.cc
>>> +++ b/gcc/opts.cc
>>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
>>> /* In this file all option sets are explicit.  */
>>> #undef OPTION_SET_P
>>> 
>>> +/* The list of extra functions in the C library.  */
>>> +extra_libc_function_list extra_libc_functions;
>>> +
>>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
>>> 
>>> /* Names of fundamental debug info formats indexed by enum
>>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
>>>   return flags;
>>> }
>>> 
>>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
>>> +
>>> +static void
>>> +parse_extra_libc_function (const char *arg)
>>> +{
>>> +  /* Check to see if the string matches a sub-option name.  */
>>> +  if (strcmp (arg, "memcmpeq") == 0)
>>> +    {
>>> +      extra_libc_functions.has_memcmpeq = 1;
>>> +      return;
>>> +    }
>>> +
>>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
>>> +        arg);
>>> +}
>>> +
>>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
>>> 
>>> unsigned int
>>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
>>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
>>>       break;
>>> 
>>> +    case OPT_fextra_libc_function_:
>>> +      parse_extra_libc_function (arg);
>>> +      break;
>>> +
>>>     case OPT_fprofile_generate_:
>>>       opts->x_profile_data_prefix = xstrdup (arg);
>>>       value = true;
>>> diff --git a/gcc/opts.h b/gcc/opts.h
>>> index a43ce66cffe..e8d8835ba23 100644
>>> --- a/gcc/opts.h
>>> +++ b/gcc/opts.h
>>> @@ -345,6 +345,13 @@ struct cl_option_handlers
>>> extern const char *opt_fstack_limit_symbol_arg;
>>> extern int opt_fstack_limit_register_no;
>>> 
>>> +/* The list of extra functions in the C library.  */
>>> +struct extra_libc_function_list
>>> +{
>>> +  unsigned int has_memcmpeq : 1;
>>> +};
>>> +extern extra_libc_function_list extra_libc_functions;
>>> +
>>> /* Input file names.  */
>>> 
>>> extern const char **in_fnames;
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
>>> new file mode 100644
>>> index 00000000000..487f6cd98db
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp (s1, s2, len) != 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
>>> new file mode 100644
>>> index 00000000000..1773dc2bee1
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
>>> +
>>> +#include <string.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return memcmp (s1, s2, len) == 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
>>> new file mode 100644
>>> index 00000000000..69c9537d572
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <string.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return memcmp (s1, s2, len);
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
>>> new file mode 100644
>>> index 00000000000..a448312ea96
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp (s1, s2, len) != 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
>>> new file mode 100644
>>> index 00000000000..4ef33a1c238
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <string.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return memcmp (s1, s2, len) == 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
>>> new file mode 100644
>>> index 00000000000..52304df7079
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
>>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
>>> +}
>>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
>>> new file mode 100644
>>> index 00000000000..d59765894e7
>>> --- /dev/null
>>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2" } */
>>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
>>> +
>>> +#include <stddef.h>
>>> +
>>> +int
>>> +foo (const char *s1, const char *s2, size_t len)
>>> +{
>>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
>>> +}
>>> --
>>> 2.36.1
>>> 
> 
> 
> 
> -- 
> H.J.

On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
>
>
> > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> >
> > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > <richard.guenther@gmail.com> wrote:
> >>
> >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> >>> <gcc-patches@gcc.gnu.org> wrote:
> >>>
> >>> Add -fextra-libc-function=memcmpeq to map
> >>>
> >>> extern int __memcmpeq (const void *, const void *, size_t);
> >>>
> >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> >>
> >> Humm.  Can't we instead use the presence of a declaration
> >> of __memcmpeq with a GNU standard dialect as this instead of
> >> adding a weird -fextra-libc-function= option?  Maybe that's even
> >> reasonable with a non-GNU dialect standard in effect since
> >> __ prefixed names are in the implementation namespace?
> >
> > But not all source codes include <string.h> and GCC may generate
> > memcmp directly.  How should we handle these cases?
>
> Not.  Similar as to vectorized math functions.
> I think it’s not worth optimizing for this case.

Another question.  Should we consider any __memcmpeq prototype
or just the one in the system header file?

> Richard.
>
> >
> >> Richard.
> >>
> >>> gcc/
> >>>
> >>>        * builtins.cc: Include "opts.h".
> >>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> >>>        available.
> >>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
> >>>        * common.opt: Add -fextra-libc-function=.
> >>>        * opts.cc (extra_libc_functions): New.
> >>>        (parse_extra_libc_function): New function.
> >>>        (common_handle_option): Handle -fextra-libc-function=.
> >>>        * opts.h (extra_libc_function_list): New.
> >>>        (extra_libc_functions): Likewise.
> >>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> >>>
> >>> gcc/testsuite/
> >>>
> >>>        * c-c++-common/memcmpeq-1.c: New test.
> >>>        * c-c++-common/memcmpeq-2.c: Likewise.
> >>>        * c-c++-common/memcmpeq-3.c: Likewise.
> >>>        * c-c++-common/memcmpeq-4.c: Likewise.
> >>>        * c-c++-common/memcmpeq-5.c: Likewise.
> >>>        * c-c++-common/memcmpeq-6.c: Likewise.
> >>>        * c-c++-common/memcmpeq-7.c: Likewise.
> >>> ---
> >>> gcc/builtins.cc                         |  5 ++++-
> >>> gcc/builtins.def                        |  4 ++++
> >>> gcc/common.opt                          |  4 ++++
> >>> gcc/doc/invoke.texi                     |  6 ++++++
> >>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
> >>> gcc/opts.h                              |  7 +++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> >>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> >>> 13 files changed, 125 insertions(+), 1 deletion(-)
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> >>>
> >>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> >>> index b9d89b409b8..22269318e8c 100644
> >>> --- a/gcc/builtins.cc
> >>> +++ b/gcc/builtins.cc
> >>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> >>> #include "demangle.h"
> >>> #include "gimple-range.h"
> >>> #include "pointer-query.h"
> >>> +#include "opts.h"
> >>>
> >>> struct target_builtins default_target_builtins;
> >>> #if SWITCHABLE_TARGET
> >>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> >>>        return target;
> >>>       if (fcode == BUILT_IN_MEMCMP_EQ)
> >>>        {
> >>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> >>> +         tree newdecl = builtin_decl_explicit
> >>> +           (extra_libc_functions.has_memcmpeq
> >>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> >>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> >>>        }
> >>>       break;
> >>> diff --git a/gcc/builtins.def b/gcc/builtins.def
> >>> index 005976f34e9..eb8d33b16e9 100644
> >>> --- a/gcc/builtins.def
> >>> +++ b/gcc/builtins.def
> >>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> >>>    equality with zero.  */
> >>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> >>>
> >>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> >>> +   -fextra-libc-function=memcmpeq.  */
> >>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> >>> +
> >>> /* An internal version of strcmp/strncmp, used when the result is only
> >>>    tested for equality with zero.  */
> >>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> >>> diff --git a/gcc/common.opt b/gcc/common.opt
> >>> index 7ca0cceed82..7a7631682b0 100644
> >>> --- a/gcc/common.opt
> >>> +++ b/gcc/common.opt
> >>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> >>> EnumValue
> >>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> >>>
> >>> +fextra-libc-function=
> >>> +Common Driver Joined
> >>> +Specify the extra function in the C library.
> >>> +
> >>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> >>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> >>> fpermitted-flt-eval-methods=
> >>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> >>> index 8cd5bdddc5d..fe1e3709953 100644
> >>> --- a/gcc/doc/invoke.texi
> >>> +++ b/gcc/doc/invoke.texi
> >>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> >>> -ffixed-@var{reg}  -fexceptions @gol
> >>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> >>> -fasynchronous-unwind-tables @gol
> >>> +-fextra-libc-function=memcmpeq @gol
> >>> -fno-gnu-unique @gol
> >>> -finhibit-size-directive  -fcommon  -fno-ident @gol
> >>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> >>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> >>> table is exact at each instruction boundary, so it can be used for stack
> >>> unwinding from asynchronous events (such as debugger or garbage collector).
> >>>
> >>> +@item -fextra-libc-function=memcmpeq
> >>> +@opindex fextra-libc-function
> >>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> >>> +@code{__builtin_memcmp_eq}.
> >>> +
> >>> @item -fno-gnu-unique
> >>> @opindex fno-gnu-unique
> >>> @opindex fgnu-unique
> >>> diff --git a/gcc/opts.cc b/gcc/opts.cc
> >>> index bf06a55456a..e77f0922acc 100644
> >>> --- a/gcc/opts.cc
> >>> +++ b/gcc/opts.cc
> >>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> >>> /* In this file all option sets are explicit.  */
> >>> #undef OPTION_SET_P
> >>>
> >>> +/* The list of extra functions in the C library.  */
> >>> +extra_libc_function_list extra_libc_functions;
> >>> +
> >>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> >>>
> >>> /* Names of fundamental debug info formats indexed by enum
> >>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> >>>   return flags;
> >>> }
> >>>
> >>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> >>> +
> >>> +static void
> >>> +parse_extra_libc_function (const char *arg)
> >>> +{
> >>> +  /* Check to see if the string matches a sub-option name.  */
> >>> +  if (strcmp (arg, "memcmpeq") == 0)
> >>> +    {
> >>> +      extra_libc_functions.has_memcmpeq = 1;
> >>> +      return;
> >>> +    }
> >>> +
> >>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> >>> +        arg);
> >>> +}
> >>> +
> >>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> >>>
> >>> unsigned int
> >>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> >>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> >>>       break;
> >>>
> >>> +    case OPT_fextra_libc_function_:
> >>> +      parse_extra_libc_function (arg);
> >>> +      break;
> >>> +
> >>>     case OPT_fprofile_generate_:
> >>>       opts->x_profile_data_prefix = xstrdup (arg);
> >>>       value = true;
> >>> diff --git a/gcc/opts.h b/gcc/opts.h
> >>> index a43ce66cffe..e8d8835ba23 100644
> >>> --- a/gcc/opts.h
> >>> +++ b/gcc/opts.h
> >>> @@ -345,6 +345,13 @@ struct cl_option_handlers
> >>> extern const char *opt_fstack_limit_symbol_arg;
> >>> extern int opt_fstack_limit_register_no;
> >>>
> >>> +/* The list of extra functions in the C library.  */
> >>> +struct extra_libc_function_list
> >>> +{
> >>> +  unsigned int has_memcmpeq : 1;
> >>> +};
> >>> +extern extra_libc_function_list extra_libc_functions;
> >>> +
> >>> /* Input file names.  */
> >>>
> >>> extern const char **in_fnames;
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> >>> new file mode 100644
> >>> index 00000000000..487f6cd98db
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> >>> new file mode 100644
> >>> index 00000000000..1773dc2bee1
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> >>> +
> >>> +#include <string.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return memcmp (s1, s2, len) == 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> >>> new file mode 100644
> >>> index 00000000000..69c9537d572
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <string.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return memcmp (s1, s2, len);
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> >>> new file mode 100644
> >>> index 00000000000..a448312ea96
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> >>> new file mode 100644
> >>> index 00000000000..4ef33a1c238
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <string.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return memcmp (s1, s2, len) == 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> >>> new file mode 100644
> >>> index 00000000000..52304df7079
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> >>> +}
> >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> >>> new file mode 100644
> >>> index 00000000000..d59765894e7
> >>> --- /dev/null
> >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> >>> @@ -0,0 +1,11 @@
> >>> +/* { dg-do compile } */
> >>> +/* { dg-options "-O2" } */
> >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> >>> +
> >>> +#include <stddef.h>
> >>> +
> >>> +int
> >>> +foo (const char *s1, const char *s2, size_t len)
> >>> +{
> >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> >>> +}
> >>> --
> >>> 2.36.1
> >>>
> >
> >
> >
> > --
> > H.J.

On Wed, Jun 15, 2022 at 2:44 PM H.J. Lu via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
> <richard.guenther@gmail.com> wrote:
> >
> >
> >
> > > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> > >
> > > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > > <richard.guenther@gmail.com> wrote:
> > >>
> > >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> > >>> <gcc-patches@gcc.gnu.org> wrote:
> > >>>
> > >>> Add -fextra-libc-function=memcmpeq to map
> > >>>
> > >>> extern int __memcmpeq (const void *, const void *, size_t);
> > >>>
> > >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> > >>
> > >> Humm.  Can't we instead use the presence of a declaration
> > >> of __memcmpeq with a GNU standard dialect as this instead of
> > >> adding a weird -fextra-libc-function= option?  Maybe that's even
> > >> reasonable with a non-GNU dialect standard in effect since
> > >> __ prefixed names are in the implementation namespace?
> > >
> > > But not all source codes include <string.h> and GCC may generate
> > > memcmp directly.  How should we handle these cases?
> >
> > Not.  Similar as to vectorized math functions.
> > I think it’s not worth optimizing for this case.
>
> Another question.  Should we consider any __memcmpeq prototype
> or just the one in the system header file?

An idea from https://reviews.llvm.org/D56593#3586673: -fbuiltin-__memcmpeq

This requires making -fbuiltin-function available, see
https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
("There is no corresponding -fbuiltin-function option")

I prefer an option over a magic behavior about whether a declaration exists.

> > Richard.
> >
> > >
> > >> Richard.
> > >>
> > >>> gcc/
> > >>>
> > >>>        * builtins.cc: Include "opts.h".
> > >>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> > >>>        available.
> > >>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
> > >>>        * common.opt: Add -fextra-libc-function=.
> > >>>        * opts.cc (extra_libc_functions): New.
> > >>>        (parse_extra_libc_function): New function.
> > >>>        (common_handle_option): Handle -fextra-libc-function=.
> > >>>        * opts.h (extra_libc_function_list): New.
> > >>>        (extra_libc_functions): Likewise.
> > >>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> > >>>
> > >>> gcc/testsuite/
> > >>>
> > >>>        * c-c++-common/memcmpeq-1.c: New test.
> > >>>        * c-c++-common/memcmpeq-2.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-3.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-4.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-5.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-6.c: Likewise.
> > >>>        * c-c++-common/memcmpeq-7.c: Likewise.
> > >>> ---
> > >>> gcc/builtins.cc                         |  5 ++++-
> > >>> gcc/builtins.def                        |  4 ++++
> > >>> gcc/common.opt                          |  4 ++++
> > >>> gcc/doc/invoke.texi                     |  6 ++++++
> > >>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
> > >>> gcc/opts.h                              |  7 +++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> > >>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> > >>> 13 files changed, 125 insertions(+), 1 deletion(-)
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> > >>>
> > >>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> > >>> index b9d89b409b8..22269318e8c 100644
> > >>> --- a/gcc/builtins.cc
> > >>> +++ b/gcc/builtins.cc
> > >>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> > >>> #include "demangle.h"
> > >>> #include "gimple-range.h"
> > >>> #include "pointer-query.h"
> > >>> +#include "opts.h"
> > >>>
> > >>> struct target_builtins default_target_builtins;
> > >>> #if SWITCHABLE_TARGET
> > >>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> > >>>        return target;
> > >>>       if (fcode == BUILT_IN_MEMCMP_EQ)
> > >>>        {
> > >>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> > >>> +         tree newdecl = builtin_decl_explicit
> > >>> +           (extra_libc_functions.has_memcmpeq
> > >>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> > >>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> > >>>        }
> > >>>       break;
> > >>> diff --git a/gcc/builtins.def b/gcc/builtins.def
> > >>> index 005976f34e9..eb8d33b16e9 100644
> > >>> --- a/gcc/builtins.def
> > >>> +++ b/gcc/builtins.def
> > >>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> > >>>    equality with zero.  */
> > >>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> > >>>
> > >>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> > >>> +   -fextra-libc-function=memcmpeq.  */
> > >>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> > >>> +
> > >>> /* An internal version of strcmp/strncmp, used when the result is only
> > >>>    tested for equality with zero.  */
> > >>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> > >>> diff --git a/gcc/common.opt b/gcc/common.opt
> > >>> index 7ca0cceed82..7a7631682b0 100644
> > >>> --- a/gcc/common.opt
> > >>> +++ b/gcc/common.opt
> > >>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> > >>> EnumValue
> > >>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> > >>>
> > >>> +fextra-libc-function=
> > >>> +Common Driver Joined
> > >>> +Specify the extra function in the C library.
> > >>> +
> > >>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> > >>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> > >>> fpermitted-flt-eval-methods=
> > >>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > >>> index 8cd5bdddc5d..fe1e3709953 100644
> > >>> --- a/gcc/doc/invoke.texi
> > >>> +++ b/gcc/doc/invoke.texi
> > >>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> > >>> -ffixed-@var{reg}  -fexceptions @gol
> > >>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> > >>> -fasynchronous-unwind-tables @gol
> > >>> +-fextra-libc-function=memcmpeq @gol
> > >>> -fno-gnu-unique @gol
> > >>> -finhibit-size-directive  -fcommon  -fno-ident @gol
> > >>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> > >>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> > >>> table is exact at each instruction boundary, so it can be used for stack
> > >>> unwinding from asynchronous events (such as debugger or garbage collector).
> > >>>
> > >>> +@item -fextra-libc-function=memcmpeq
> > >>> +@opindex fextra-libc-function
> > >>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> > >>> +@code{__builtin_memcmp_eq}.
> > >>> +
> > >>> @item -fno-gnu-unique
> > >>> @opindex fno-gnu-unique
> > >>> @opindex fgnu-unique
> > >>> diff --git a/gcc/opts.cc b/gcc/opts.cc
> > >>> index bf06a55456a..e77f0922acc 100644
> > >>> --- a/gcc/opts.cc
> > >>> +++ b/gcc/opts.cc
> > >>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> > >>> /* In this file all option sets are explicit.  */
> > >>> #undef OPTION_SET_P
> > >>>
> > >>> +/* The list of extra functions in the C library.  */
> > >>> +extra_libc_function_list extra_libc_functions;
> > >>> +
> > >>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> > >>>
> > >>> /* Names of fundamental debug info formats indexed by enum
> > >>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> > >>>   return flags;
> > >>> }
> > >>>
> > >>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> > >>> +
> > >>> +static void
> > >>> +parse_extra_libc_function (const char *arg)
> > >>> +{
> > >>> +  /* Check to see if the string matches a sub-option name.  */
> > >>> +  if (strcmp (arg, "memcmpeq") == 0)
> > >>> +    {
> > >>> +      extra_libc_functions.has_memcmpeq = 1;
> > >>> +      return;
> > >>> +    }
> > >>> +
> > >>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> > >>> +        arg);
> > >>> +}
> > >>> +
> > >>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> > >>>
> > >>> unsigned int
> > >>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> > >>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> > >>>       break;
> > >>>
> > >>> +    case OPT_fextra_libc_function_:
> > >>> +      parse_extra_libc_function (arg);
> > >>> +      break;
> > >>> +
> > >>>     case OPT_fprofile_generate_:
> > >>>       opts->x_profile_data_prefix = xstrdup (arg);
> > >>>       value = true;
> > >>> diff --git a/gcc/opts.h b/gcc/opts.h
> > >>> index a43ce66cffe..e8d8835ba23 100644
> > >>> --- a/gcc/opts.h
> > >>> +++ b/gcc/opts.h
> > >>> @@ -345,6 +345,13 @@ struct cl_option_handlers
> > >>> extern const char *opt_fstack_limit_symbol_arg;
> > >>> extern int opt_fstack_limit_register_no;
> > >>>
> > >>> +/* The list of extra functions in the C library.  */
> > >>> +struct extra_libc_function_list
> > >>> +{
> > >>> +  unsigned int has_memcmpeq : 1;
> > >>> +};
> > >>> +extern extra_libc_function_list extra_libc_functions;
> > >>> +
> > >>> /* Input file names.  */
> > >>>
> > >>> extern const char **in_fnames;
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > >>> new file mode 100644
> > >>> index 00000000000..487f6cd98db
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > >>> new file mode 100644
> > >>> index 00000000000..1773dc2bee1
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > >>> +
> > >>> +#include <string.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return memcmp (s1, s2, len) == 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > >>> new file mode 100644
> > >>> index 00000000000..69c9537d572
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <string.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return memcmp (s1, s2, len);
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > >>> new file mode 100644
> > >>> index 00000000000..a448312ea96
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > >>> new file mode 100644
> > >>> index 00000000000..4ef33a1c238
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <string.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return memcmp (s1, s2, len) == 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > >>> new file mode 100644
> > >>> index 00000000000..52304df7079
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > >>> +}
> > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > >>> new file mode 100644
> > >>> index 00000000000..d59765894e7
> > >>> --- /dev/null
> > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > >>> @@ -0,0 +1,11 @@
> > >>> +/* { dg-do compile } */
> > >>> +/* { dg-options "-O2" } */
> > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > >>> +
> > >>> +#include <stddef.h>
> > >>> +
> > >>> +int
> > >>> +foo (const char *s1, const char *s2, size_t len)
> > >>> +{
> > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > >>> +}
> > >>> --
> > >>> 2.36.1
> > >>>
> > >
> > >
> > >
> > > --
> > > H.J.
>
>
>
> --
> H.J.

On Thu, Jun 16, 2022 at 1:38 AM Fangrui Song <maskray@google.com> wrote:
>
> On Wed, Jun 15, 2022 at 2:44 PM H.J. Lu via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
> > <richard.guenther@gmail.com> wrote:
> > >
> > >
> > >
> > > > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> > > >
> > > > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > > > <richard.guenther@gmail.com> wrote:
> > > >>
> > > >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> > > >>> <gcc-patches@gcc.gnu.org> wrote:
> > > >>>
> > > >>> Add -fextra-libc-function=memcmpeq to map
> > > >>>
> > > >>> extern int __memcmpeq (const void *, const void *, size_t);
> > > >>>
> > > >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> > > >>
> > > >> Humm.  Can't we instead use the presence of a declaration
> > > >> of __memcmpeq with a GNU standard dialect as this instead of
> > > >> adding a weird -fextra-libc-function= option?  Maybe that's even
> > > >> reasonable with a non-GNU dialect standard in effect since
> > > >> __ prefixed names are in the implementation namespace?
> > > >
> > > > But not all source codes include <string.h> and GCC may generate
> > > > memcmp directly.  How should we handle these cases?
> > >
> > > Not.  Similar as to vectorized math functions.
> > > I think it’s not worth optimizing for this case.
> >
> > Another question.  Should we consider any __memcmpeq prototype
> > or just the one in the system header file?

Any.

> An idea from https://reviews.llvm.org/D56593#3586673: -fbuiltin-__memcmpeq
>
> This requires making -fbuiltin-function available, see
> https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
> ("There is no corresponding -fbuiltin-function option")
>
> I prefer an option over a magic behavior about whether a declaration exists.

But we already have this behavior for multiple cases.  It's also the only
way that in practice __memcmpeq will be used - _nobody_ (but maybe
special crafted SPEC peak runs) will add explicit -fbuiltin-__memcmpeq.

Richard.

> > > Richard.
> > >
> > > >
> > > >> Richard.
> > > >>
> > > >>> gcc/
> > > >>>
> > > >>>        * builtins.cc: Include "opts.h".
> > > >>>        (expand_builtin): Generate BUILT_IN_MEMCMP_EQ if __memcmpeq is
> > > >>>        available.
> > > >>>        * builtins.def (BUILT_IN___MEMCMPEQ): New.
> > > >>>        * common.opt: Add -fextra-libc-function=.
> > > >>>        * opts.cc (extra_libc_functions): New.
> > > >>>        (parse_extra_libc_function): New function.
> > > >>>        (common_handle_option): Handle -fextra-libc-function=.
> > > >>>        * opts.h (extra_libc_function_list): New.
> > > >>>        (extra_libc_functions): Likewise.
> > > >>>        * doc/invoke.texi: Document -fextra-libc-function=memcmpeq.
> > > >>>
> > > >>> gcc/testsuite/
> > > >>>
> > > >>>        * c-c++-common/memcmpeq-1.c: New test.
> > > >>>        * c-c++-common/memcmpeq-2.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-3.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-4.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-5.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-6.c: Likewise.
> > > >>>        * c-c++-common/memcmpeq-7.c: Likewise.
> > > >>> ---
> > > >>> gcc/builtins.cc                         |  5 ++++-
> > > >>> gcc/builtins.def                        |  4 ++++
> > > >>> gcc/common.opt                          |  4 ++++
> > > >>> gcc/doc/invoke.texi                     |  6 ++++++
> > > >>> gcc/opts.cc                             | 23 +++++++++++++++++++++++
> > > >>> gcc/opts.h                              |  7 +++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-1.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-2.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-3.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-4.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-5.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-6.c | 11 +++++++++++
> > > >>> gcc/testsuite/c-c++-common/memcmpeq-7.c | 11 +++++++++++
> > > >>> 13 files changed, 125 insertions(+), 1 deletion(-)
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-1.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-2.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-3.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-4.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-5.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-6.c
> > > >>> create mode 100644 gcc/testsuite/c-c++-common/memcmpeq-7.c
> > > >>>
> > > >>> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> > > >>> index b9d89b409b8..22269318e8c 100644
> > > >>> --- a/gcc/builtins.cc
> > > >>> +++ b/gcc/builtins.cc
> > > >>> @@ -81,6 +81,7 @@ along with GCC; see the file COPYING3.  If not see
> > > >>> #include "demangle.h"
> > > >>> #include "gimple-range.h"
> > > >>> #include "pointer-query.h"
> > > >>> +#include "opts.h"
> > > >>>
> > > >>> struct target_builtins default_target_builtins;
> > > >>> #if SWITCHABLE_TARGET
> > > >>> @@ -7410,7 +7411,9 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
> > > >>>        return target;
> > > >>>       if (fcode == BUILT_IN_MEMCMP_EQ)
> > > >>>        {
> > > >>> -         tree newdecl = builtin_decl_explicit (BUILT_IN_MEMCMP);
> > > >>> +         tree newdecl = builtin_decl_explicit
> > > >>> +           (extra_libc_functions.has_memcmpeq
> > > >>> +            ? BUILT_IN___MEMCMPEQ : BUILT_IN_MEMCMP);
> > > >>>          TREE_OPERAND (exp, 1) = build_fold_addr_expr (newdecl);
> > > >>>        }
> > > >>>       break;
> > > >>> diff --git a/gcc/builtins.def b/gcc/builtins.def
> > > >>> index 005976f34e9..eb8d33b16e9 100644
> > > >>> --- a/gcc/builtins.def
> > > >>> +++ b/gcc/builtins.def
> > > >>> @@ -965,6 +965,10 @@ DEF_BUILTIN_STUB (BUILT_IN_ALLOCA_WITH_ALIGN_AND_MAX, "__builtin_alloca_with_ali
> > > >>>    equality with zero.  */
> > > >>> DEF_BUILTIN_STUB (BUILT_IN_MEMCMP_EQ, "__builtin_memcmp_eq")
> > > >>>
> > > >>> +/* Similar to BUILT_IN_MEMCMP_EQ, but is mapped to __memcmpeq only with
> > > >>> +   -fextra-libc-function=memcmpeq.  */
> > > >>> +DEF_EXT_LIB_BUILTIN (BUILT_IN___MEMCMPEQ, "__memcmpeq", BT_FN_INT_CONST_PTR_CONST_PTR_SIZE, ATTR_PURE_NOTHROW_NONNULL_LEAF)
> > > >>> +
> > > >>> /* An internal version of strcmp/strncmp, used when the result is only
> > > >>>    tested for equality with zero.  */
> > > >>> DEF_BUILTIN_STUB (BUILT_IN_STRCMP_EQ, "__builtin_strcmp_eq")
> > > >>> diff --git a/gcc/common.opt b/gcc/common.opt
> > > >>> index 7ca0cceed82..7a7631682b0 100644
> > > >>> --- a/gcc/common.opt
> > > >>> +++ b/gcc/common.opt
> > > >>> @@ -1587,6 +1587,10 @@ Enum(excess_precision) String(standard) Value(EXCESS_PRECISION_STANDARD)
> > > >>> EnumValue
> > > >>> Enum(excess_precision) String(16) Value(EXCESS_PRECISION_FLOAT16)
> > > >>>
> > > >>> +fextra-libc-function=
> > > >>> +Common Driver Joined
> > > >>> +Specify the extra function in the C library.
> > > >>> +
> > > >>> ; Whether we permit the extended set of values for FLT_EVAL_METHOD
> > > >>> ; introduced in ISO/IEC TS 18661-3, or limit ourselves to those in C99/C11.
> > > >>> fpermitted-flt-eval-methods=
> > > >>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > > >>> index 8cd5bdddc5d..fe1e3709953 100644
> > > >>> --- a/gcc/doc/invoke.texi
> > > >>> +++ b/gcc/doc/invoke.texi
> > > >>> @@ -676,6 +676,7 @@ Objective-C and Objective-C++ Dialects}.
> > > >>> -ffixed-@var{reg}  -fexceptions @gol
> > > >>> -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables @gol
> > > >>> -fasynchronous-unwind-tables @gol
> > > >>> +-fextra-libc-function=memcmpeq @gol
> > > >>> -fno-gnu-unique @gol
> > > >>> -finhibit-size-directive  -fcommon  -fno-ident @gol
> > > >>> -fpcc-struct-return  -fpic  -fPIC  -fpie  -fPIE  -fno-plt @gol
> > > >>> @@ -17250,6 +17251,11 @@ Generate unwind table in DWARF format, if supported by target machine.  The
> > > >>> table is exact at each instruction boundary, so it can be used for stack
> > > >>> unwinding from asynchronous events (such as debugger or garbage collector).
> > > >>>
> > > >>> +@item -fextra-libc-function=memcmpeq
> > > >>> +@opindex fextra-libc-function
> > > >>> +Generate @code{__memcmpeq}, which was added to GLIBC 2.35, for
> > > >>> +@code{__builtin_memcmp_eq}.
> > > >>> +
> > > >>> @item -fno-gnu-unique
> > > >>> @opindex fno-gnu-unique
> > > >>> @opindex fgnu-unique
> > > >>> diff --git a/gcc/opts.cc b/gcc/opts.cc
> > > >>> index bf06a55456a..e77f0922acc 100644
> > > >>> --- a/gcc/opts.cc
> > > >>> +++ b/gcc/opts.cc
> > > >>> @@ -38,6 +38,9 @@ along with GCC; see the file COPYING3.  If not see
> > > >>> /* In this file all option sets are explicit.  */
> > > >>> #undef OPTION_SET_P
> > > >>>
> > > >>> +/* The list of extra functions in the C library.  */
> > > >>> +extra_libc_function_list extra_libc_functions;
> > > >>> +
> > > >>> static void set_Wstrict_aliasing (struct gcc_options *opts, int onoff);
> > > >>>
> > > >>> /* Names of fundamental debug info formats indexed by enum
> > > >>> @@ -2269,6 +2272,22 @@ parse_no_sanitize_attribute (char *value)
> > > >>>   return flags;
> > > >>> }
> > > >>>
> > > >>> +/* Parse -fextra-libc-function= suboptions from ARG.  */
> > > >>> +
> > > >>> +static void
> > > >>> +parse_extra_libc_function (const char *arg)
> > > >>> +{
> > > >>> +  /* Check to see if the string matches a sub-option name.  */
> > > >>> +  if (strcmp (arg, "memcmpeq") == 0)
> > > >>> +    {
> > > >>> +      extra_libc_functions.has_memcmpeq = 1;
> > > >>> +      return;
> > > >>> +    }
> > > >>> +
> > > >>> +  error ("unrecognized argument to %<-fextra-libc-function=%>: %qs",
> > > >>> +        arg);
> > > >>> +}
> > > >>> +
> > > >>> /* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
> > > >>>
> > > >>> unsigned int
> > > >>> @@ -2940,6 +2959,10 @@ common_handle_option (struct gcc_options *opts,
> > > >>>       SET_OPTION_IF_UNSET (opts, opts_set, flag_profile_correction, value);
> > > >>>       break;
> > > >>>
> > > >>> +    case OPT_fextra_libc_function_:
> > > >>> +      parse_extra_libc_function (arg);
> > > >>> +      break;
> > > >>> +
> > > >>>     case OPT_fprofile_generate_:
> > > >>>       opts->x_profile_data_prefix = xstrdup (arg);
> > > >>>       value = true;
> > > >>> diff --git a/gcc/opts.h b/gcc/opts.h
> > > >>> index a43ce66cffe..e8d8835ba23 100644
> > > >>> --- a/gcc/opts.h
> > > >>> +++ b/gcc/opts.h
> > > >>> @@ -345,6 +345,13 @@ struct cl_option_handlers
> > > >>> extern const char *opt_fstack_limit_symbol_arg;
> > > >>> extern int opt_fstack_limit_register_no;
> > > >>>
> > > >>> +/* The list of extra functions in the C library.  */
> > > >>> +struct extra_libc_function_list
> > > >>> +{
> > > >>> +  unsigned int has_memcmpeq : 1;
> > > >>> +};
> > > >>> +extern extra_libc_function_list extra_libc_functions;
> > > >>> +
> > > >>> /* Input file names.  */
> > > >>>
> > > >>> extern const char **in_fnames;
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-1.c b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..487f6cd98db
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-2.c b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..1773dc2bee1
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <string.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return memcmp (s1, s2, len) == 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-3.c b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..69c9537d572
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <string.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return memcmp (s1, s2, len);
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-4.c b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..a448312ea96
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-4.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp (s1, s2, len) != 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-5.c b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..4ef33a1c238
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-5.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <string.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return memcmp (s1, s2, len) == 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-6.c b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..52304df7079
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2 -fextra-libc-function=memcmpeq" } */
> > > >>> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > > >>> +}
> > > >>> diff --git a/gcc/testsuite/c-c++-common/memcmpeq-7.c b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > > >>> new file mode 100644
> > > >>> index 00000000000..d59765894e7
> > > >>> --- /dev/null
> > > >>> +++ b/gcc/testsuite/c-c++-common/memcmpeq-7.c
> > > >>> @@ -0,0 +1,11 @@
> > > >>> +/* { dg-do compile } */
> > > >>> +/* { dg-options "-O2" } */
> > > >>> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> > > >>> +
> > > >>> +#include <stddef.h>
> > > >>> +
> > > >>> +int
> > > >>> +foo (const char *s1, const char *s2, size_t len)
> > > >>> +{
> > > >>> +  return __builtin_memcmp_eq (s1, s2, len) != 0;
> > > >>> +}
> > > >>> --
> > > >>> 2.36.1
> > > >>>
> > > >
> > > >
> > > >
> > > > --
> > > > H.J.
> >
> >
> >
> > --
> > H.J.
>
>
>
> --
> 宋方睿

On Mon, Jun 20, 2022 at 2:39 AM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Thu, Jun 16, 2022 at 1:38 AM Fangrui Song <maskray@google.com> wrote:
> >
> > On Wed, Jun 15, 2022 at 2:44 PM H.J. Lu via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > On Mon, Jun 13, 2022 at 9:01 AM Richard Biener
> > > <richard.guenther@gmail.com> wrote:
> > > >
> > > >
> > > >
> > > > > Am 13.06.2022 um 16:36 schrieb H.J. Lu <hjl.tools@gmail.com>:
> > > > >
> > > > > On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
> > > > > <richard.guenther@gmail.com> wrote:
> > > > >>
> > > > >>> On Tue, Jun 7, 2022 at 9:02 PM H.J. Lu via Gcc-patches
> > > > >>> <gcc-patches@gcc.gnu.org> wrote:
> > > > >>>
> > > > >>> Add -fextra-libc-function=memcmpeq to map
> > > > >>>
> > > > >>> extern int __memcmpeq (const void *, const void *, size_t);
> > > > >>>
> > > > >>> which was added to GLIBC 2.35, to __builtin_memcmp_eq.
> > > > >>
> > > > >> Humm.  Can't we instead use the presence of a declaration
> > > > >> of __memcmpeq with a GNU standard dialect as this instead of
> > > > >> adding a weird -fextra-libc-function= option?  Maybe that's even
> > > > >> reasonable with a non-GNU dialect standard in effect since
> > > > >> __ prefixed names are in the implementation namespace?
> > > > >
> > > > > But not all source codes include <string.h> and GCC may generate
> > > > > memcmp directly.  How should we handle these cases?
> > > >
> > > > Not.  Similar as to vectorized math functions.
> > > > I think it’s not worth optimizing for this case.
> > >
> > > Another question.  Should we consider any __memcmpeq prototype
> > > or just the one in the system header file?
>
> Any.

Here is the v2 patch:

https://gcc.gnu.org/pipermail/gcc-patches/2022-June/596881.html

> > An idea from https://reviews.llvm.org/D56593#3586673: -fbuiltin-__memcmpeq
> >
> > This requires making -fbuiltin-function available, see
> > https://gcc.gnu.org/onlinedocs/gcc/C-Dialect-Options.html
> > ("There is no corresponding -fbuiltin-function option")
> >
> > I prefer an option over a magic behavior about whether a declaration exists.
>
> But we already have this behavior for multiple cases.  It's also the only
> way that in practice __memcmpeq will be used - _nobody_ (but maybe
> special crafted SPEC peak runs) will add explicit -fbuiltin-__memcmpeq.
>
> Richard.

Thanks.