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
>
