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Show hash table stats when -fmem-report

Hello list,

I ported a patch from last year's GSOC to current trunk, removing deprecated hash tables and adding some new ones. I also backed out a change that reduced collisions by decreasing load factor because it had created controversy, so this patch should be easily applicable.

CC'd whoever is relevant with subsystems or had commented on this last year. Some notes:

* Is it OK that I included <assert.h> in libiberty's hashtab.c?
* Many hash tables are created with htab_create_ggc(), for example referenced_vars and default_defs in tree-ssa.c. I collect statistics in delete_tree_ssa() but maybe some are not deallocated in there but automatically garbage collected?
* Obviously hash table sizes are inflated where two entries might reference the same element (for example in symtab_hash) but I don't handle this.
* Maybe the best overall solution would be to add a string parameter to htab_create*() and store statistics in an internal hash table according to this string. Statistics would then be printed for all hash tables by iterating this internal table. Since it would cause a significant slowdown, -fmem-report would be better as a compile-time option than a run-time one. This is probably an overkill so I think I'll skip it.

Thanks, Dimitris

2012-05-21 Dimitrios Apostolou <>

	Print various statistics about hash tables when called with
	-fmem-report. If the tables are created once use
	htab_dump_statistics(), if they are created/destroyed multiple
	times then introduce global variables to track statistics.

	* cgraph.c, cgraph.h:
	(cgraph_dump_stats): New function to dump stats about hash tables.
	* gcc/symtab.c, cgraph.h:
	(symtab_dump_stats): New function to dump stats about hash tables.
	* cgraph.c: (call_site_hash_{num,expands,searches,collisions}):
	New globals to keep statistics about call_site_hash hash tables.
	(cgraph_remove_node_callees,cgraph_remove_node): if (mem_report)
	then keep statistics about hash tables.
	* cselib.c, cselib.h (cselib_dump_stats): New function to dump
	stats about cselib_hash_table.
	* cselib.c (cselib_htab_{num,expands,searches,collisions}): New
	globals to keep hash table statistics.
	(cselib_finish): if (mem_report) keep hash table statistics.
	* dwarf2out.c (dwarf2out_finish): Call htab_dump_statistics() if
	* emit-rtl.c, emit-rtl.h (mem_attrs_dump_stats): New function to
	dump statistics about mem_attrs_htab hash table.
	* tree.h, tree-ssa.c (tree_ssa_dump_stats): New function to print
	statistics about all referenced_vars and default_defs hash tables.
	* tree-ssa.c (default_defs_{num,expands,searches,collisions})
	(referenced_vars_{num,expands,searches,collisions}): new globals
	to keep statistics about hash tables.
	(delete_tree_ssa): Keep statistics for hash tables by
	increasing the new global variables.
	* tree.c (dump_tree_statistics): Call tree_ssa_dump_stats().
	(print_type_hash_statistics): Used the new htab_dump_statistics()
	* var-tracking.c (vars_htab_{num,expands,searches,collisions})
	(cv_htab_{num,expands,searches,collisions}): new globals to keep
	hash table statistics.
	(shared_hash_destroy, vt_finalize): Keep statistics by
	increasing values of new global variables if -fmem-report.
	* var-tracking.c, rtl.h (vt_dump_stats): New function to dump
	stats about vars->htab, dropped_variables and value_chains hash
	* toplev.c: Included cselib.h for cselib_dump_stats().
	(dump_memory_report): Call all the above functions to provide
	better statistics.

* hashtab.c, hashtab.h: Added "expands" variable to htab_t for
tracking total times the hash table was expanded.
* hashtab.c, hashtab.h (htab_dump_statistics, htab_collisions_num)
(htab_searches_num, htab_expands_num): New functions for statistics.
* hashtab.c: Included assert.h for checks in htab_dump_statistics.
* cgraph.h, varpool.c (varpool_dump_stats): New function to dump
stats about varpool_hash hash table.

	* libcpp/symtab.c, symtab.h: Added "expands" variable to
	hash_table type for tracking total times the hash table was
	* symtab.c (ht_dump_statistics): Beautified stats output.

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