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      1 //===-- msan_chained_origin_depot.cc -----------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // A storage for chained origins.
     11 //===----------------------------------------------------------------------===//
     12 
     13 #include "msan_chained_origin_depot.h"
     14 
     15 #include "sanitizer_common/sanitizer_stackdepotbase.h"
     16 
     17 namespace __msan {
     18 
     19 struct ChainedOriginDepotDesc {
     20   u32 here_id;
     21   u32 prev_id;
     22 };
     23 
     24 struct ChainedOriginDepotNode {
     25   ChainedOriginDepotNode *link;
     26   u32 id;
     27   u32 here_id;
     28   u32 prev_id;
     29 
     30   typedef ChainedOriginDepotDesc args_type;
     31   bool eq(u32 hash, const args_type &args) const {
     32     return here_id == args.here_id && prev_id == args.prev_id;
     33   }
     34   static uptr storage_size(const args_type &args) {
     35     return sizeof(ChainedOriginDepotNode);
     36   }
     37   /* This is murmur2 hash for the 64->32 bit case.
     38      It does not behave all that well because the keys have a very biased
     39      distribution (I've seen 7-element buckets with the table only 14% full).
     40 
     41      here_id is built of
     42      * (1 bits) Reserved, zero.
     43      * (8 bits) Part id = bits 13..20 of the hash value of here_id's key.
     44      * (23 bits) Sequential number (each part has each own sequence).
     45 
     46      prev_id has either the same distribution as here_id (but with 3:8:21)
     47      split, or one of two reserved values (-1) or (-2). Either case can
     48      dominate depending on the workload.
     49   */
     50   static u32 hash(const args_type &args) {
     51     const u32 m = 0x5bd1e995;
     52     const u32 seed = 0x9747b28c;
     53     const u32 r = 24;
     54     u32 h = seed;
     55     u32 k = args.here_id;
     56     k *= m;
     57     k ^= k >> r;
     58     k *= m;
     59     h *= m;
     60     h ^= k;
     61 
     62     k = args.prev_id;
     63     k *= m;
     64     k ^= k >> r;
     65     k *= m;
     66     h *= m;
     67     h ^= k;
     68 
     69     h ^= h >> 13;
     70     h *= m;
     71     h ^= h >> 15;
     72     return h;
     73   }
     74   static bool is_valid(const args_type &args) { return true; }
     75   void store(const args_type &args, u32 other_hash) {
     76     here_id = args.here_id;
     77     prev_id = args.prev_id;
     78   }
     79   args_type load() const {
     80     args_type ret = {here_id, prev_id};
     81     return ret;
     82   }
     83   struct Handle {
     84     ChainedOriginDepotNode *node_;
     85     Handle() : node_(0) {}
     86     explicit Handle(ChainedOriginDepotNode *node) : node_(node) {}
     87     bool valid() { return node_; }
     88     u32 id() { return node_->id; }
     89     int here_id() { return node_->here_id; }
     90     int prev_id() { return node_->prev_id; }
     91   };
     92   Handle get_handle() { return Handle(this); }
     93 
     94   typedef Handle handle_type;
     95 };
     96 
     97 static StackDepotBase<ChainedOriginDepotNode, 4, 20> chainedOriginDepot;
     98 
     99 StackDepotStats *ChainedOriginDepotGetStats() {
    100   return chainedOriginDepot.GetStats();
    101 }
    102 
    103 bool ChainedOriginDepotPut(u32 here_id, u32 prev_id, u32 *new_id) {
    104   ChainedOriginDepotDesc desc = {here_id, prev_id};
    105   bool inserted;
    106   ChainedOriginDepotNode::Handle h = chainedOriginDepot.Put(desc, &inserted);
    107   *new_id = h.valid() ? h.id() : 0;
    108   return inserted;
    109 }
    110 
    111 // Retrieves a stored stack trace by the id.
    112 u32 ChainedOriginDepotGet(u32 id, u32 *other) {
    113   ChainedOriginDepotDesc desc = chainedOriginDepot.Get(id);
    114   *other = desc.prev_id;
    115   return desc.here_id;
    116 }
    117 
    118 void ChainedOriginDepotLockAll() {
    119   chainedOriginDepot.LockAll();
    120 }
    121 
    122 void ChainedOriginDepotUnlockAll() {
    123   chainedOriginDepot.UnlockAll();
    124 }
    125 
    126 }  // namespace __msan
    127