From da22f50517faeb3fc185521631e3b86b89bd60ec Mon Sep 17 00:00:00 2001 From: Jan Hubicka Date: Wed, 9 Jul 2014 21:09:50 +0200 Subject: [PATCH] * lto-streamer-out.c (hash_scc): Avoid quadratic hashing loop. From-SVN: r212404 --- gcc/ChangeLog | 4 ++++ gcc/lto-streamer-out.c | 34 ++++++++++------------------------ 2 files changed, 14 insertions(+), 24 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index d166c486036..96b437fbcf4 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,7 @@ +2014-07-08 Jan Hubicka + + * lto-streamer-out.c (hash_scc): Avoid quadratic hashing loop. + 2014-07-08 Jan Hubicka Revert: diff --git a/gcc/lto-streamer-out.c b/gcc/lto-streamer-out.c index 30645627d02..bd289090bae 100644 --- a/gcc/lto-streamer-out.c +++ b/gcc/lto-streamer-out.c @@ -1131,32 +1131,18 @@ hash_scc (struct streamer_tree_cache_d *cache, unsigned first, unsigned size) /* Sort the SCC of type, hash pairs so that when we mix in all members of the SCC the hash value becomes independent on - the order we visited the SCC. Disregard hashes equal to - the hash of the tree we mix into because we cannot guarantee - a stable sort for those across different TUs. */ + the order we visited the SCC. Produce hash of the whole SCC as + combination of hashes of individual elements. Then combine that hash into + hash of each element, so othewise identically looking elements from two + different SCCs are distinguished. */ qsort (&sccstack[first], size, sizeof (scc_entry), scc_entry_compare); - hashval_t *tem = XALLOCAVEC (hashval_t, size); + + hashval_t scc_hash = sccstack[first].hash; + for (unsigned i = 1; i < size; ++i) + scc_hash = iterative_hash_hashval_t (scc_hash, + sccstack[first+i].hash); for (unsigned i = 0; i < size; ++i) - { - hashval_t hash = sccstack[first+i].hash; - hashval_t orig_hash = hash; - unsigned j; - /* Skip same hashes. */ - for (j = i + 1; - j < size && sccstack[first+j].hash == orig_hash; ++j) - ; - for (; j < size; ++j) - hash = iterative_hash_hashval_t (sccstack[first+j].hash, hash); - for (j = 0; sccstack[first+j].hash != orig_hash; ++j) - hash = iterative_hash_hashval_t (sccstack[first+j].hash, hash); - tem[i] = hash; - } - hashval_t scc_hash = 0; - for (unsigned i = 0; i < size; ++i) - { - sccstack[first+i].hash = tem[i]; - scc_hash = iterative_hash_hashval_t (tem[i], scc_hash); - } + sccstack[first+i].hash = iterative_hash_hashval_t (sccstack[first+i].hash, scc_hash); return scc_hash; }