[gcc(refs/users/marxin/heads/marxin-gcc-benchmark-branch)] c++: Reduce memory consumption for large static arrays.

[Martin Liska]

https://gcc.gnu.org/g:d2b9548f38c77edc29ab0e24e516f1fb341ecea7

commit d2b9548f38c77edc29ab0e24e516f1fb341ecea7
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jan 30 18:49:29 2020 -0500

    c++: Reduce memory consumption for large static arrays.
    
    PR14179 and the C counterpart PR12245 are about memory consumption of very
    large file-scope arrays.  Recently, location wrappers increased memory
    consumption significantly: in an array of integer constants, each one will
    have a location wrapper, which added up to over 500MB in the 14179
    testcase.  For this kind of testcase tracking these locations isn't worth
    the cost, so this patch turns the wrappers off after 256 elements; any array
    that size or larger isn't likely to be interested in the location of
    individual integer constants.
    
            PR c++/14179
            * parser.c (cp_parser_initializer_list): Suppress location wrappers
            after 256 elements.

Diff:
---
 gcc/cp/ChangeLog |  6 ++++++
 gcc/cp/parser.c  | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index f260d5d5d80..f8140885dab 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-01-31  Jason Merrill  <jason@redhat.com>
+
+	PR c++/14179
+	* parser.c (cp_parser_initializer_list): Suppress location wrappers
+	after 256 elements.
+
 2020-01-29  Jason Merrill  <jason@redhat.com>
 
 	PR c++/82521
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index bd8e524f078..e0f72302e5e 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -23311,6 +23311,9 @@ cp_parser_initializer_list (cp_parser* parser, bool* non_constant_p,
   /* Assume all of the expressions are constant.  */
   *non_constant_p = false;
 
+  unsigned nelts = 0;
+  int suppress = suppress_location_wrappers;
+
   /* Parse the rest of the list.  */
   while (true)
     {
@@ -23450,6 +23453,19 @@ cp_parser_initializer_list (cp_parser* parser, bool* non_constant_p,
       if (token->type == CPP_CLOSE_BRACE)
 	break;
 
+      /* Suppress location wrappers in a long initializer to save memory
+	 (14179).  The cutoff is chosen arbitrarily.  */
+      const unsigned loc_max = 256;
+      unsigned incr = 1;
+      if (TREE_CODE (initializer) == CONSTRUCTOR)
+	/* Look one level down because it's easy.  Looking deeper would require
+	   passing down a nelts pointer, and I don't think multi-level massive
+	   initializers are common enough to justify this.  */
+	incr = CONSTRUCTOR_NELTS (initializer);
+      nelts += incr;
+      if (nelts >= loc_max && (nelts - incr) < loc_max)
+	++suppress_location_wrappers;
+
       /* Consume the `,' token.  */
       cp_lexer_consume_token (parser->lexer);
     }
@@ -23479,6 +23495,8 @@ cp_parser_initializer_list (cp_parser* parser, bool* non_constant_p,
 	  IDENTIFIER_MARKED (designator) = 0;
     }
 
+  suppress_location_wrappers = suppress;
+
   *designated = first_designator != NULL_TREE;
   return v;
 }