This decreases the integer-share-limit to make sure the TREE_VEC we allocate for the small cached integers has a reasonable size for our GC memory allocator. With the current value (256) and a reduced testcase from PR54146 we see
tree.c:1224 (build_int_cst_wide) 40: 0.0% 0: 0.0% 35443680: 8.7% 11635920:39.0% 9305 thus 39% overhead (oops, that TREE_VEC has size 2080). Reducing this to 251 yields tree.c:1224 (build_int_cst_wide) 40: 0.0% 0: 0.0% 11698864: 3.0% 33696: 0.2% 9154 which is much nicer (size 2048 for signed ints, 1020 bytes on 32bit hosts if I counted correctly). I'm queueing this for a bootstrap & regtest run. Richard. 2012-08-16 Richard Guenther <rguent...@suse.de> * params.def (integer-share-limit): Decrease from 256 to 251, add rationale. Index: gcc/params.def =================================================================== *** gcc/params.def (revision 190442) --- gcc/params.def (working copy) *************** DEFPARAM(PARAM_MAX_LAST_VALUE_RTL, *** 638,648 **** /* INTEGER_CST nodes are shared for values [{-1,0} .. N) for {signed,unsigned} integral types. This determines N. ! Experimentation shows 256 to be a good value. */ DEFPARAM (PARAM_INTEGER_SHARE_LIMIT, "integer-share-limit", "The upper bound for sharing integer constants", ! 256, 2, 2) DEFPARAM (PARAM_SSP_BUFFER_SIZE, "ssp-buffer-size", --- 638,649 ---- /* INTEGER_CST nodes are shared for values [{-1,0} .. N) for {signed,unsigned} integral types. This determines N. ! Experimentation shows 251 to be a good value that generates the ! least amount of garbage for allocating the TREE_VEC storage. */ DEFPARAM (PARAM_INTEGER_SHARE_LIMIT, "integer-share-limit", "The upper bound for sharing integer constants", ! 251, 2, 2) DEFPARAM (PARAM_SSP_BUFFER_SIZE, "ssp-buffer-size",