[lld] r314090 - Compute string hashes early and cache them.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Sun Sep 24 18:42:57 2017
New Revision: 314090

URL: http://llvm.org/viewvc/llvm-project?rev=314090&view=rev
Log:
Compute string hashes early and cache them.

This change alone speeds up linking of Clang debug build with -gdb-index
by 1.2 seconds, from 12.5 seconds to 11.3 seconds. (Without -gdb-index,
lld takes 8.5 seconds to link the same input files.)

Modified:
    lld/trunk/ELF/SyntheticSections.cpp
    lld/trunk/ELF/SyntheticSections.h

Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=314090&r1=314089&r2=314090&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Sun Sep 24 18:42:57 2017
@@ -1756,9 +1756,12 @@ readPubNamesAndTypes(DWARFContext &Dwarf
   std::vector<GdbIndexChunk::NameTypeEntry> Ret;
   for (StringRef Sec : {Sec1, Sec2}) {
     DWARFDebugPubTable Table(Sec, Config->IsLE, true);
-    for (const DWARFDebugPubTable::Set &Set : Table.getData())
-      for (const DWARFDebugPubTable::Entry &Ent : Set.Entries)
-        Ret.push_back({Ent.Name, Ent.Descriptor.toBits()});
+    for (const DWARFDebugPubTable::Set &Set : Table.getData()) {
+      for (const DWARFDebugPubTable::Entry &Ent : Set.Entries) {
+        CachedHashStringRef S(Ent.Name, computeGdbHash(Ent.Name));
+        Ret.push_back({S, Ent.Descriptor.toBits()});
+      }
+    }
   }
   return Ret;
 }
@@ -1787,12 +1790,10 @@ std::vector<std::set<uint32_t>> GdbIndex
 
   for (GdbIndexChunk &Chunk : Chunks) {
     for (GdbIndexChunk::NameTypeEntry &Ent : Chunk.NamesAndTypes) {
-      uint32_t Hash = computeGdbHash(Ent.Name);
       size_t Offset = StringPool.add(Ent.Name);
-
       GdbSymbol *&Sym = SymbolMap[Offset];
       if (!Sym) {
-        Sym = make<GdbSymbol>(GdbSymbol{Hash, Offset, Ret.size()});
+        Sym = make<GdbSymbol>(GdbSymbol{Ent.Name.hash(), Offset, Ret.size()});
         Ret.resize(Ret.size() + 1);
       }
       Ret[Sym->CuVectorIndex].insert((Ent.Type << 24) | Idx);

Modified: lld/trunk/ELF/SyntheticSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.h?rev=314090&r1=314089&r2=314090&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.h (original)
+++ lld/trunk/ELF/SyntheticSections.h Sun Sep 24 18:42:57 2017
@@ -510,7 +510,7 @@ struct GdbIndexChunk {
   };
 
   struct NameTypeEntry {
-    StringRef Name;
+    llvm::CachedHashStringRef Name;
     uint8_t Type;
   };