Hi!
The following patch (again, on top of the #embed patchset, so
https://gcc.gnu.org/pipermail/gcc-patches/2024-June/655012.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-June/655013.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-July/657049.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-July/657053.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-July/658137.html
https://gcc.gnu.org/pipermail/gcc-patches/2024-August/659331.html
) attempts to optimize compilation of large {{{,un}signed ,}char,std::byte}
array initializers when not using #embed in the source.
Unlike the C patch which is done during the parsing of initializers this
is done when lexing tokens into an array, because C++ lexes all tokens
upfront and so by the time we parse the initializers we already have 16
bytes per token allocated (i.e. 32 extra compile time memory bytes per
one byte in the array).
The drawback is again that it can result in worse locations for diagnostics
(-Wnarrowing, -Wconversion) when initializing signed char arrays with values
128..255. Not really sure what to do about this though unlike the C case,
the locations would need to be preserved through reshape_init* and perhaps
till template instantiation.
For #embed, there is just a single location_t (could be range of the
directive), for diagnostics perhaps we could extend it to say byte xyz of
the file embedded here or something like that, but the optimization done by
this patch, either we'd need to bump the minimum limit at which to try it,
or say temporarily allocate a location_t array for each byte and then clear
it when we no longer need it or something.
I've been using the same testcases as for C, with #embed of 100'000'000
bytes:
time ./cc1plus -quiet -O2 -o test4a.s2 test4a.c
real 0m0.972s
user 0m0.578s
sys 0m0.195s
with xxd -i alternative of the same data without this patch it consumed
around 13.2GB of RAM and
time ./cc1plus -quiet -O2 -o test4b.s4 test4b.c
real 3m47.968s
user 3m41.907s
sys 0m5.015s
and the same with this patch it consumed around 3.7GB of RAM and
time ./cc1plus -quiet -O2 -o test4b.s3 test4b.c
real 0m24.772s
user 0m23.118s
sys 0m1.495s
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2024-08-03 Jakub Jelinek <ja...@redhat.com>
* parser.cc (cp_lexer_new_main): Attempt to optimize large sequences
of CPP_NUMBER with int type and values 0-255 separated by CPP_COMMA
into CPP_EMBED with RAW_DATA_CST u.value.
--- gcc/cp/parser.cc.jj 2024-08-02 11:34:20.343813689 +0200
+++ gcc/cp/parser.cc 2024-08-02 19:35:12.380611787 +0200
@@ -734,6 +734,12 @@ cp_lexer_new_main (void)
gcc_assert (!the_parser);
the_parser = cp_parser_new (lexer);
+ unsigned raw_data_tokens = 0;
+ char *raw_data_buf = NULL;
+ const unsigned int raw_data_max_len
+ = 131072 - offsetof (struct tree_string, str) - 1;
+ const unsigned int raw_data_min_len = 128;
+
/* Get the remaining tokens from the preprocessor. */
while (tok->type != CPP_EOF)
{
@@ -742,6 +748,72 @@ cp_lexer_new_main (void)
module_token_lang (tok->type, tok->keyword, tok->u.value,
tok->location, filter);
+ /* Attempt to optimize long lists of 0-255 integers
+ separated by commas into CPP_EMBED. */
+ recheck:
+ if (tok->type == CPP_NUMBER
+ && (raw_data_tokens & 1) == 0
+ && TREE_CODE (tok->u.value) == INTEGER_CST
+ && TREE_TYPE (tok->u.value) == integer_type_node
+ && !wi::neg_p (wi::to_wide (tok->u.value))
+ && wi::to_widest (tok->u.value) <= UCHAR_MAX
+ && raw_data_tokens < raw_data_max_len * 2)
+ {
+ raw_data_tokens++;
+ if (raw_data_tokens >= raw_data_min_len * 2 + 3)
+ {
+ unsigned int len = lexer->buffer->length ();
+ unsigned int new_len;
+ if (raw_data_tokens == raw_data_min_len * 2 + 3)
+ {
+ if (raw_data_buf == NULL)
+ raw_data_buf = XNEWVEC (char, raw_data_max_len);
+ for (unsigned i = len - raw_data_tokens, j = 0;
+ i < len; i += 2, ++j)
+ raw_data_buf[j]
+ = (char) tree_to_uhwi ((*lexer->buffer)[i].u.value);
+ new_len = len - raw_data_tokens + 5;
+ }
+ else
+ {
+ raw_data_buf[raw_data_tokens / 2]
+ = (char) tree_to_uhwi (tok->u.value);
+ new_len = len - 2;
+ }
+ (*lexer->buffer)[new_len - 2] = (*lexer->buffer)[len - 2];
+ (*lexer->buffer)[new_len - 1] = (*lexer->buffer)[len - 1];
+ lexer->buffer->truncate (new_len);
+ }
+ }
+ else if (tok->type == CPP_COMMA
+ && (raw_data_tokens & 1) == 1)
+ raw_data_tokens++;
+ else if (raw_data_tokens >= raw_data_min_len * 2 + 3)
+ {
+ unsigned last_number = (raw_data_tokens & 1);
+ unsigned int idx = lexer->buffer->length () - 4 - !last_number;
+ if (!last_number)
+ --raw_data_tokens;
+ raw_data_tokens = raw_data_tokens / 2 + 1;
+ tree raw = make_node (RAW_DATA_CST);
+ TREE_TYPE (raw) = integer_type_node;
+ RAW_DATA_LENGTH (raw) = raw_data_tokens - 2;
+ tree owner = build_string (raw_data_tokens, raw_data_buf);
+ TREE_TYPE (owner) = build_array_type_nelts (unsigned_char_type_node,
+ raw_data_tokens);
+ RAW_DATA_OWNER (raw) = owner;
+ RAW_DATA_POINTER (raw) = TREE_STRING_POINTER (owner) + 1;
+ (*lexer->buffer)[idx].type = CPP_EMBED;
+ (*lexer->buffer)[idx].u.value = raw;
+ raw_data_tokens = 0;
+ goto recheck;
+ }
+ else if (raw_data_tokens)
+ {
+ raw_data_tokens = 0;
+ goto recheck;
+ }
+
/* Check for early pragmas that need to be handled now. */
if (tok->type == CPP_PRAGMA_EOL)
cp_lexer_handle_early_pragma (lexer);
@@ -750,6 +822,8 @@ cp_lexer_new_main (void)
cp_lexer_get_preprocessor_token (C_LEX_STRING_NO_JOIN, tok);
}
+ XDELETEVEC (raw_data_buf);
+
lexer->next_token = lexer->buffer->address ();
lexer->last_token = lexer->next_token
+ lexer->buffer->length ()
Jakub
