[compiler-rt] r212704 - [msan] Switch chained origins hash to murmur2.

[Evgeniy Stepanov]

Author: eugenis
Date: Thu Jul 10 06:02:33 2014
New Revision: 212704

URL: http://llvm.org/viewvc/llvm-project?rev=212704&view=rev
Log:
[msan] Switch chained origins hash to murmur2.

Modified:
    compiler-rt/trunk/lib/msan/msan_chained_origin_depot.cc

Modified: compiler-rt/trunk/lib/msan/msan_chained_origin_depot.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/msan/msan_chained_origin_depot.cc?rev=212704&r1=212703&r2=212704&view=diff
==============================================================================
--- compiler-rt/trunk/lib/msan/msan_chained_origin_depot.cc (original)
+++ compiler-rt/trunk/lib/msan/msan_chained_origin_depot.cc Thu Jul 10 06:02:33 2014
@@ -19,7 +19,30 @@ namespace __msan {
 struct ChainedOriginDepotDesc {
   u32 here_id;
   u32 prev_id;
-  u32 hash() const { return (here_id * 0x1f1f1f1f) ^ prev_id; }
+  u32 hash() const {
+    const u32 m = 0x5bd1e995;
+    const u32 seed = 0x9747b28c;
+    const u32 r = 24;
+    u32 h = seed;
+    u32 k = here_id;
+    k *= m;
+    k ^= k >> r;
+    k *= m;
+    h *= m;
+    h ^= k;
+
+    k = prev_id;
+    k *= m;
+    k ^= k >> r;
+    k *= m;
+    h *= m;
+    h ^= k;
+
+    h ^= h >> 13;
+    h *= m;
+    h ^= h >> 15;
+    return h;
+  }
   bool is_valid() { return true; }
 };