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| author | Jan Hubicka <jh@suse.cz> | 2020-05-22 12:31:34 +0200 |
|---|---|---|
| committer | Jan Hubicka <jh@suse.cz> | 2020-05-22 12:31:34 +0200 |
| commit | 1089a367c4b05b5e3f072adca8913904ed65928c (patch) | |
| tree | dc3005726895465873d326c1c26a4189f61e28da /gcc | |
| parent | 47273df0bcdd552385f25049dce71943aac8321e (diff) | |
| download | gcc-1089a367c4b05b5e3f072adca8913904ed65928c.zip gcc-1089a367c4b05b5e3f072adca8913904ed65928c.tar.gz gcc-1089a367c4b05b5e3f072adca8913904ed65928c.tar.bz2 | |
Fix hashing of prestreamed nodes
this patch seems to solve basically all collisions while building cc1.
From:
[WPA] read 3312246 unshared trees
[WPA] read 1144381 mergeable SCCs of average size 4.833785
[WPA] 8843938 tree bodies read in total
[WPA] tree SCC table: size 524287, 197767 elements, collision ratio: 0.506446
[WPA] tree SCC max chain length 43 (size 1)
[WPA] Compared 946614 SCCs, 775077 collisions (0.818789)
to
[WPA] read 3314520 unshared trees
[WPA] read 1144763 mergeable SCCs of average size 4.835021
[WPA] 8849473 tree bodies read in total
[WPA] tree SCC table: size 524287, 200574 elements, collision ratio: 0.486418
[WPA] tree SCC max chain length 2 (size 1)
[WPA] Compared 944189 SCCs, 179 collisions (0.000190)
The problem is that preloaded nodes all have hash code 0 because
cache->nodes.length is not updated while streaming out.
I also added an arbitrary constant to avoid clash with constant of 0 used to
hash NULL pointers and 1 used to hash pointers inside SCC.
* tree-streamer.c (record_common_node): Fix hash value of pre-streamed
nodes.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/tree-streamer.c | 9 |
2 files changed, 10 insertions, 4 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 820240f..d22e9aa 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,10 @@ 2020-05-22 Jan Hubicka <hubicka@ucw.cz> + * tree-streamer.c (record_common_node): Fix hash value of pre-streamed + nodes. + +2020-05-22 Jan Hubicka <hubicka@ucw.cz> + * lto-streamer-in.c (lto_read_tree): Do not stream end markers. (lto_input_scc): Optimize streaming of entry lengths. * lto-streamer-out.c (lto_write_tree): Do not stream end markers diff --git a/gcc/tree-streamer.c b/gcc/tree-streamer.c index f6181fa..b0afa1d 100644 --- a/gcc/tree-streamer.c +++ b/gcc/tree-streamer.c @@ -299,10 +299,11 @@ record_common_node (struct streamer_tree_cache_d *cache, tree node) if (!node) node = error_mark_node; - /* ??? FIXME, devise a better hash value. But the hash needs to be equal - for all frontend and lto1 invocations. So just use the position - in the cache as hash value. */ - streamer_tree_cache_append (cache, node, cache->nodes.length ()); + /* This hash needs to be equal for all frontend and lto1 invocations. So + just use the position in the cache as hash value. + Small integers are used by hash_tree to record positions within scc + hash. Values are not in same range. */ + streamer_tree_cache_append (cache, node, cache->next_idx + 0xc001); switch (TREE_CODE (node)) { |