[PATCH] D35413: [LLD][ELF] Add DefinedInThunk to SymbolBody to remove need for hash lookup

[Peter Smith via Phabricator via llvm-commits]

peter.smith created this revision.
Herald added a subscriber: emaste.

When doing thunk creation, if a relocation target is defined in a thunk we need to find a way of getting to the Thunk object. This change removes the
DenseMap in ThunkCreator that stored the mapping in preference for storing a pointer to the Thunk in SymbolBody. This saves a hash lookup at the expense of adding a pointer to SymbolBody.

This was suggested in https://reviews.llvm.org/D34692


https://reviews.llvm.org/D35413

Files:
  ELF/Relocations.cpp
  ELF/Relocations.h
  ELF/Symbols.h


Index: ELF/Symbols.h
===================================================================
--- ELF/Symbols.h
+++ ELF/Symbols.h
@@ -33,6 +33,8 @@
 class OutputSection;
 template <class ELFT> class SharedFile;
 
+class Thunk;
+
 struct Symbol;
 
 // The base class for real symbol classes.
@@ -90,7 +92,8 @@
 
   // The file from which this symbol was created.
   InputFile *File = nullptr;
-
+  // The Thunk that this symbol is defined in, nullptr if not defined in Thunk
+  Thunk *DefinedInThunk = nullptr;
   uint32_t DynsymIndex = 0;
   uint32_t GotIndex = -1;
   uint32_t GotPltIndex = -1;
Index: ELF/Relocations.h
===================================================================
--- ELF/Relocations.h
+++ ELF/Relocations.h
@@ -151,10 +151,6 @@
   // Record all the available Thunks for a Symbol
   llvm::DenseMap<SymbolBody *, std::vector<Thunk *>> ThunkedSymbols;
 
-  // Find a Thunk from the Thunks symbol definition, we can use this to find
-  // the Thunk from a relocation to the Thunks symbol definition.
-  llvm::DenseMap<SymbolBody *, Thunk *> Thunks;
-
   // Track InputSections that have an inline ThunkSection placed in front
   // an inline ThunkSection may have control fall through to the section below
   // so we need to make sure that there is only one of them.
Index: ELF/Relocations.cpp
===================================================================
--- ELF/Relocations.cpp
+++ ELF/Relocations.cpp
@@ -1235,7 +1235,7 @@
 // was originally to a Thunk, but is no longer in range we revert the
 // relocation back to its original non-Thunk target.
 bool ThunkCreator::normalizeExistingThunk(Relocation &Rel, uint64_t Src) {
-  if (Thunk *ET = Thunks.lookup(Rel.Sym)) {
+  if (Thunk *ET = Rel.Sym->DefinedInThunk) {
     if (Target->inBranchRange(Rel.Type, Src, Rel.Sym->getVA()))
       return true;
     Rel.Sym = &ET->Destination;
@@ -1313,7 +1313,7 @@
               else
                 TS = getISRThunkSec(OS, IS, ISR, Rel.Type, Src);
               TS->addThunk(T);
-              Thunks[T->ThunkSym] = T;
+              T->ThunkSym->DefinedInThunk = T;
             }
             // Redirect relocation to Thunk, we never go via the PLT to a Thunk
             Rel.Sym = T->ThunkSym;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D35413.106635.patch
Type: text/x-patch
Size: 2220 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170714/3ff7278d/attachment.bin>