[Bug libstdc++/80290] [6/7 Regression] g++ uses unreasonable amount of memory compiling nested string maps

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80290

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Reduced:

#include <utility>

typedef std::pair<unsigned, std::pair<const char *, std::pair<const char *,
std::pair<const char *, std::pair<const char *, const char *> > > > > FruMap;

#define INIT { 1, \
  { "/system/chassis/motherboard/cpu0", \
    { "xyz.openbmc_project.Inventory.Decorator.Asset", \
      { "PartNumber", \
        {"IPMIFruSection","Board"}, \
      }, \
    } \
  }, \
}

extern const FruMap frus[] = {
INIT,
INIT,
INIT,
INIT,
INIT,
};


GCC 5:

Execution times (seconds)
 phase setup             :   0.00 ( 0%) usr   0.00 ( 0%) sys   0.01 (17%) wall 
  1323 kB (15%) ggc
 phase parsing           :   0.04 (100%) usr   0.01 (100%) sys   0.05 (83%)
wall    7520 kB (84%) ggc
 |name lookup            :   0.01 (25%) usr   0.00 ( 0%) sys   0.03 (50%) wall 
   581 kB ( 7%) ggc
 |overload resolution    :   0.01 (25%) usr   0.00 ( 0%) sys   0.01 (17%) wall 
  1867 kB (21%) ggc
 parser (global)         :   0.02 (50%) usr   0.00 ( 0%) sys   0.02 (33%) wall 
  2692 kB (30%) ggc
 parser struct body      :   0.01 (25%) usr   0.00 ( 0%) sys   0.00 ( 0%) wall 
   911 kB (10%) ggc
 template instantiation  :   0.01 (25%) usr   0.01 (100%) sys   0.03 (50%) wall
   3239 kB (36%) ggc
 TOTAL                 :   0.04             0.01             0.06              
8941 kB


GCC 6:

Execution times (seconds)
 phase setup             :   0.00 ( 0%) usr   0.00 ( 0%) sys   0.01 ( 1%) wall 
  1397 kB ( 1%) ggc
 phase parsing           :   0.62 (98%) usr   0.19 (100%) sys   0.81 (96%) wall
 125355 kB (99%) ggc
 phase opt and generate  :   0.01 ( 2%) usr   0.00 ( 0%) sys   0.02 ( 2%) wall 
   231 kB ( 0%) ggc
 |name lookup            :   0.01 ( 2%) usr   0.01 ( 5%) sys   0.00 ( 0%) wall 
  1155 kB ( 1%) ggc
 |overload resolution    :   0.24 (38%) usr   0.04 (21%) sys   0.27 (32%) wall 
 68949 kB (54%) ggc
 callgraph construction  :   0.01 ( 2%) usr   0.00 ( 0%) sys   0.01 ( 1%) wall 
   231 kB ( 0%) ggc
 callgraph optimization  :   0.00 ( 0%) usr   0.00 ( 0%) sys   0.01 ( 1%) wall 
     0 kB ( 0%) ggc
 preprocessing           :   0.01 ( 2%) usr   0.00 ( 0%) sys   0.01 ( 1%) wall 
   187 kB ( 0%) ggc
 parser (global)         :   0.36 (57%) usr   0.10 (53%) sys   0.55 (65%) wall 
103307 kB (81%) ggc
 parser struct body      :   0.01 ( 2%) usr   0.00 ( 0%) sys   0.01 ( 1%) wall 
  1227 kB ( 1%) ggc
 parser inl. meth. body  :   0.01 ( 2%) usr   0.00 ( 0%) sys   0.00 ( 0%) wall 
    95 kB ( 0%) ggc
 template instantiation  :   0.21 (33%) usr   0.09 (47%) sys   0.24 (29%) wall 
 19154 kB (15%) ggc
 symout                  :   0.02 ( 3%) usr   0.00 ( 0%) sys   0.00 ( 0%) wall 
  1387 kB ( 1%) ggc
 TOTAL                 :   0.63             0.19             0.84            
127016 kB