[PATCH v2] Enable __memcmpeq after seeing __memcmpeq prototype

Richard Biener richard.guenther@gmail.com
Fri Jul 1 07:51:46 GMT 2022


On Mon, Jun 20, 2022 at 5:44 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> extern int __memcmpeq (const void *, const void *, size_t);
>
> was was added to GLIBC 2.35.  Expand BUILT_IN_MEMCMP_EQ to __memcmpeq
> after seeing __memcmpeq prototype

Can you instead use builtin_decl_declared_p (), see how frontends
set that via set_builtin_decl_declared_p?

> gcc/
>
>         * builtins.cc (have_memcmpeq_prototype): New.
>         (expand_builtin): Issue an error for BUILT_IN___MEMCMPEQ if
>         there is no __memcmpeq prototype.  Expand BUILT_IN_MEMCMP_EQ
>         to BUILT_IN___MEMCMP_EQ if there is __memcmpeq prototype.
>         * builtins.def (BUILT_IN___MEMCMPEQ): New.
>         * builtins.h (have_memcmpeq_prototype): New.
>
> gcc/c/
>
>         * c-decl.cc (diagnose_mismatched_decls): Set
>         have_memcmpeq_prototype to true after seeing __memcmpeq prototype.
>
> gcc/cp/
>
>         *  decl.cc (duplicate_decls): Set have_memcmpeq_prototype to true
>         after seeing __memcmpeq prototype.
>
> 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.h: Likewise.
> ---
>  gcc/builtins.cc                         | 17 ++++++++++++++++-
>  gcc/builtins.def                        |  3 +++
>  gcc/builtins.h                          |  3 +++
>  gcc/c/c-decl.cc                         | 25 ++++++++++++++++++-------
>  gcc/cp/decl.cc                          |  5 +++++
>  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 | 10 ++++++++++
>  gcc/testsuite/c-c++-common/memcmpeq.h   | 11 +++++++++++
>  12 files changed, 121 insertions(+), 8 deletions(-)
>  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.h
>
> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> index 971b18c3745..96e283e5847 100644
> --- a/gcc/builtins.cc
> +++ b/gcc/builtins.cc
> @@ -104,6 +104,9 @@ builtin_info_type builtin_info[(int)END_BUILTINS];
>  /* Non-zero if __builtin_constant_p should be folded right away.  */
>  bool force_folding_builtin_constant_p;
>
> +/* True if there is a __memcmpeq prototype.  */
> +bool have_memcmpeq_prototype;
> +
>  static int target_char_cast (tree, char *);
>  static int apply_args_size (void);
>  static int apply_result_size (void);
> @@ -7392,6 +7395,15 @@ expand_builtin (tree exp, rtx target, rtx subtarget, machine_mode mode,
>         return target;
>        break;
>
> +    case BUILT_IN___MEMCMPEQ:
> +      if (!have_memcmpeq_prototype)
> +       {
> +         error ("use of %<__builtin___memcmpeq ()%> without "
> +                "%<__memcmpeq%> prototype");
> +         return const0_rtx;
> +       }
> +      break;
> +
>      /* Expand it as BUILT_IN_MEMCMP_EQ first. If not successful, change it
>         back to a BUILT_IN_STRCMP. Remember to delete the 3rd parameter
>         when changing it to a strcmp call.  */
> @@ -7445,7 +7457,10 @@ 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
> +           (have_memcmpeq_prototype
> +            ? 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..95642c6acdf 100644
> --- a/gcc/builtins.def
> +++ b/gcc/builtins.def
> @@ -965,6 +965,9 @@ 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.  */
> +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/builtins.h b/gcc/builtins.h
> index 5ad830c9fbf..e3e80b33f6d 100644
> --- a/gcc/builtins.h
> +++ b/gcc/builtins.h
> @@ -49,6 +49,9 @@ extern struct target_builtins *this_target_builtins;
>  /* Non-zero if __builtin_constant_p should be folded right away.  */
>  extern bool force_folding_builtin_constant_p;
>
> +/* True if there is a __memcmpeq prototype.  */
> +extern bool have_memcmpeq_prototype;
> +
>  extern bool called_as_built_in (tree);
>  extern bool get_object_alignment_1 (tree, unsigned int *,
>                                     unsigned HOST_WIDE_INT *);
> diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
> index ae8990c138f..cc66d254017 100644
> --- a/gcc/c/c-decl.cc
> +++ b/gcc/c/c-decl.cc
> @@ -2140,13 +2140,24 @@ diagnose_mismatched_decls (tree newdecl, tree olddecl,
>           return false;
>         }
>      }
> -  /* Warn about enum/integer type mismatches.  They are compatible types
> -     (C2X 6.7.2.2/5), but may pose portability problems.  */
> -  else if (enum_and_int_p && TREE_CODE (newdecl) != TYPE_DECL)
> -    warned = warning_at (DECL_SOURCE_LOCATION (newdecl),
> -                        OPT_Wenum_int_mismatch,
> -                        "conflicting types for %q+D due to enum/integer "
> -                        "mismatch; have %qT", newdecl, newtype);
> +  else
> +    {
> +      /* Enable __memcmpeq after seeing its prototype.  */
> +      if (TREE_CODE (olddecl) == FUNCTION_DECL
> +         && fndecl_built_in_p (olddecl, BUILT_IN_NORMAL)
> +         && !C_DECL_DECLARED_BUILTIN (olddecl)
> +         && DECL_FUNCTION_CODE (olddecl) == BUILT_IN___MEMCMPEQ)
> +       have_memcmpeq_prototype = true;
> +
> +      /* Warn about enum/integer type mismatches.  They are compatible
> +        types (C2X 6.7.2.2/5), but may pose portability problems.  */
> +      if (enum_and_int_p && TREE_CODE (newdecl) != TYPE_DECL)
> +       warned = warning_at (DECL_SOURCE_LOCATION (newdecl),
> +                            OPT_Wenum_int_mismatch,
> +                            "conflicting types for %q+D due to "
> +                            "enum/integer mismatch; have %qT",
> +                            newdecl, newtype);
> +    }
>
>    /* Redeclaration of a type is a constraint violation (6.7.2.3p1),
>       but silently ignore the redeclaration if either is in a system
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 29fc36534c2..051e83e3540 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -1719,6 +1719,11 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
>
>           type = cp_build_type_attribute_variant (type, attribs);
>           TREE_TYPE (newdecl) = TREE_TYPE (olddecl) = type;
> +
> +         /* Enable __memcmpeq after seeing its prototype.  */
> +         if (fndecl_built_in_p (olddecl, BUILT_IN_NORMAL)
> +             && DECL_FUNCTION_CODE (olddecl) == BUILT_IN___MEMCMPEQ)
> +           have_memcmpeq_prototype = true;
>         }
>
>        /* If a function is explicitly declared "throw ()", propagate that to
> 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..14622f0d765
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-1.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include "memcmpeq.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..f57f279f173
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-2.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler "__memcmpeq" } } */
> +
> +#include "memcmpeq.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..2ca2131c23a
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-3.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-not "__memcmpeq" } } */
> +
> +#include "memcmpeq.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..d59765894e7
> --- /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_eq (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..cb12358cd87
> --- /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 "__memcmpeq" } } */
> +
> +#include "memcmpeq.h"
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin___memcmpeq (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..8f983c05a44
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq-6.c
> @@ -0,0 +1,10 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +#include <stddef.h>
> +
> +int
> +foo (const char *s1, const char *s2, size_t len)
> +{
> +  return __builtin___memcmpeq (s1, s2, len) != 0; /* { dg-error "__builtin___memcmpeq" } */
> +}
> diff --git a/gcc/testsuite/c-c++-common/memcmpeq.h b/gcc/testsuite/c-c++-common/memcmpeq.h
> new file mode 100644
> index 00000000000..3f731a4806b
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/memcmpeq.h
> @@ -0,0 +1,11 @@
> +#include <string.h>
> +
> +#if __cplusplus
> +extern "C" {
> +#endif
> +
> +extern int __memcmpeq (const void *, const void *, size_t);
> +
> +#if __cplusplus
> +}
> +#endif
> --
> 2.36.1
>


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