> Am 24.08.2024 um 16:47 schrieb Alexander Monakov <amona...@ispras.ru>:
>
> Tie together the two functions that ensure tail padding with
> search_line_ssse3 via CPP_BUFFER_PADDING macro.
Ok
Richard
> libcpp/ChangeLog:
>
> * internal.h (CPP_BUFFER_PADDING): New macro; use it ...
> * charset.cc (_cpp_convert_input): ...here, and ...
> * files.cc (read_file_guts): ...here, and ...
> * lex.cc (search_line_ssse3): here.
> ---
> libcpp/charset.cc | 7 +------
> libcpp/files.cc | 6 +-----
> libcpp/internal.h | 7 +++++++
> libcpp/lex.cc | 4 ++--
> 4 files changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/libcpp/charset.cc b/libcpp/charset.cc
> index 79072877cb..fd57f61398 100644
> --- a/libcpp/charset.cc
> +++ b/libcpp/charset.cc
> @@ -3093,7 +3093,7 @@ _cpp_convert_input (cpp_reader *pfile, const char
> *input_charset,
> struct cset_converter input_cset;
> struct _cpp_strbuf to;
> unsigned char *buffer;
> - size_t pad;
> + size_t pad = CPP_BUFFER_PADDING;
>
> input_cset = init_iconv_desc (pfile, SOURCE_CHARSET, input_charset);
> if (input_cset.func == convert_no_conversion)
> @@ -3130,11 +3130,6 @@ _cpp_convert_input (cpp_reader *pfile, const char
> *input_charset,
> }
> }
>
> -#ifdef HAVE_SSSE3
> - pad = 64;
> -#else
> - pad = 16;
> -#endif
> /* Resize buffer if we allocated substantially too much, or if we
> don't have enough space for the following padding, which allows
> search_line_fast to use (possibly misaligned) vector loads. */
> diff --git a/libcpp/files.cc b/libcpp/files.cc
> index 3775091d25..fc66b9c3d7 100644
> --- a/libcpp/files.cc
> +++ b/libcpp/files.cc
> @@ -732,11 +732,7 @@ read_file_guts (cpp_reader *pfile, _cpp_file *file,
> location_t loc,
> the majority of C source files. */
> size = 8 * 1024;
>
> -#ifdef HAVE_SSSE3
> - pad = 64;
> -#else
> - pad = 16;
> -#endif
> + pad = CPP_BUFFER_PADDING;
> /* The '+ PAD' here is space for the final '\n' and PAD-1 bytes of padding,
> allowing search_line_fast to use (possibly misaligned) vector loads. */
> buf = XNEWVEC (uchar, size + pad);
> diff --git a/libcpp/internal.h b/libcpp/internal.h
> index a20215c570..ad0a5d5d4e 100644
> --- a/libcpp/internal.h
> +++ b/libcpp/internal.h
> @@ -322,6 +322,13 @@ struct _cpp_line_note
> unsigned int type;
> };
>
> +/* Tail padding required by search_line_fast alternatives. */
> +#ifdef HAVE_SSSE3
> +#define CPP_BUFFER_PADDING 64
> +#else
> +#define CPP_BUFFER_PADDING 16
> +#endif
> +
> /* Represents the contents of a file cpplib has read in. */
> struct cpp_buffer
> {
> diff --git a/libcpp/lex.cc b/libcpp/lex.cc
> index f2d47d112b..7f0f8d0773 100644
> --- a/libcpp/lex.cc
> +++ b/libcpp/lex.cc
> @@ -359,8 +359,8 @@ search_line_ssse3 (const uchar *s, const uchar *end
> ATTRIBUTE_UNUSED)
> "host character encoding is ASCII");
>
> v16qi d1, d2, t1, t2;
> - /* Unaligned loads. Reading beyond the final newline is safe,
> - since files.cc:read_file_guts pads the allocation. */
> + /* Unaligned loads, potentially using padding after the final newline. */
> + static_assert (CPP_BUFFER_PADDING >= 64, "");
> d1 = *(const v16qi_u *)s;
> d2 = *(const v16qi_u *)(s + 16);
> unsigned m1, m2, found;
> --
> 2.46.0
>
