On Mon, Jun 13, 2022 at 3:11 AM Richard Biener
<richard.guent...@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
> >
--
H.J.
