Re: [rfa] ENUM BITFIELD, here it comes again

[Michael Elizabeth Chastain <mec@shout.net>]

Okay.  Andrew, how is this?

Michael C

2003-08-21  Micahel Chastain  <mec@shout.net>

	* symtab.h: Add comments about space usage.  Identify
	the space-critical structures.

Index: symtab.h
===================================================================
RCS file: /cvs/src/src/gdb/symtab.h,v
retrieving revision 1.78
diff -c -3 -p -r1.78 symtab.h
*** symtab.h	20 Aug 2003 17:39:18 -0000	1.78
--- symtab.h	21 Aug 2003 17:40:00 -0000
*************** struct blockvector;
*** 35,47 ****
  struct axs_value;
  struct agent_expr;
  
  /* Define a structure for the information that is common to all symbol types,
     including minimal symbols, partial symbols, and full symbols.  In a
     multilanguage environment, some language specific information may need to
!    be recorded along with each symbol.
  
!    These fields are ordered to encourage good packing, since we frequently
!    have tens or hundreds of thousands of these.  */
  
  struct general_symbol_info
  {
--- 35,70 ----
  struct axs_value;
  struct agent_expr;
  
+ /* Some of the structures in this file are space critical.
+    The space-critical structures are:
+ 
+      struct general_symbol_info
+      struct symbol
+      struct partial_symbol
+ 
+    These structures are layed out to encourage good packing.
+    They use ENUM_BITFIELD and short int fields, and they order the
+    structure members so that fields less than a word are next
+    to each other so they can be packed together. */
+ 
+ /* Rearranged: used ENUM_BITFIELD and rearranged field order in
+    all the space critical structures (plus struct minimal_symbol).
+    Memory usage dropped from 99360768 bytes to 90001408 bytes.
+    I measured this with before-and-after tests of
+    "HEAD-old-gdb -readnow HEAD-old-gdb" and
+    "HEAD-new-gdb -readnow HEAD-old-gdb" on native i686-pc-linux-gnu,
+    red hat linux 8, with LD_LIBRARY_PATH=/usr/lib/debug,
+    typing "maint space 1" at the first command prompt.
+    --chastain 2003-08-21  */
+ 
+ 
+ 
  /* Define a structure for the information that is common to all symbol types,
     including minimal symbols, partial symbols, and full symbols.  In a
     multilanguage environment, some language specific information may need to
!    be recorded along with each symbol. */
  
! /* This structure is space critical.  See space comments at the top. */
  
  struct general_symbol_info
  {
*************** struct alias_list
*** 557,562 ****
--- 580,587 ----
    struct alias_list *next;
  };
  
+ /* This structure is space critical.  See space comments at the top. */
+ 
  struct symbol
  {
  
*************** struct symbol
*** 637,642 ****
--- 662,669 ----
     Each partial_symbol sits in a partial_symtab, all of which are chained
     on a  partial symtab list and which points to the corresponding 
     normal symtab once the partial_symtab has been referenced.  */
+ 
+ /* This structure is space critical.  See space comments at the top. */
  
  struct partial_symbol
  {