[PATCH] D30085: [LLD][ELF] Alloc local symbols to be added to the SymTab after global symbols

[Peter Smith via Phabricator via llvm-commits]

peter.smith created this revision.

This change moves the SymbolBodies with isLocal() == true before the global symbols then calculating NumLocals rather than assuming all locals are added before globals and the first NumLocals have isLocal() == true.

This permits the thunk creation code, that generates local symbols, to be moved after the pass that adds global symbols from synthetics to the symbol table.


https://reviews.llvm.org/D30085

Files:
  ELF/SyntheticSections.cpp
  ELF/Writer.cpp


Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -1112,13 +1112,7 @@
   if (In<ELFT>::Iplt && !In<ELFT>::Iplt->empty())
     In<ELFT>::Iplt->addSymbols();
 
-  // Some architectures use small displacements for jump instructions.
-  // It is linker's responsibility to create thunks containing long
-  // jump instructions if jump targets are too far. Create thunks.
-  if (Target->NeedsThunks)
-    createThunks<ELFT>(OutputSections);
-
-  // Now that we have defined all possible symbols including linker-
+  // Now that we have defined all possible global symbols including linker-
   // synthesized ones. Visit all symbols to give the finishing touches.
   for (Symbol *S : Symtab<ELFT>::X->getSymbols()) {
     SymbolBody *Body = S->body();
@@ -1168,6 +1162,12 @@
     fixHeaders();
   }
 
+  // Some architectures use small displacements for jump instructions.
+  // It is linker's responsibility to create thunks containing long
+  // jump instructions if jump targets are too far. Create thunks.
+  if (Target->NeedsThunks)
+    createThunks<ELFT>(OutputSections);
+
   // Fill other section headers. The dynamic table is finalized
   // at the end because some tags like RELSZ depend on result
   // of finalizing other sections.
Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -1085,9 +1085,17 @@
 
 template <class ELFT> void SymbolTableSection<ELFT>::finalize() {
   this->OutSec->Link = this->Link = StrTabSec.OutSec->SectionIndex;
-  this->OutSec->Info = this->Info = NumLocals + 1;
   this->OutSec->Entsize = this->Entsize;
 
+  if (!StrTabSec.isDynamic()) {
+    // All explictly added STB_LOCAL symbols without a Symbol are first
+    auto It = std::stable_partition(
+        Symbols.begin(), Symbols.end(),
+        [](const SymbolTableEntry &S) { return S.Symbol->isLocal(); });
+    NumLocals = It - Symbols.begin();
+  }
+  this->OutSec->Info = this->Info = 1 + NumLocals;
+
   if (Config->Relocatable)
     return;
 
@@ -1122,7 +1130,6 @@
 
 template <class ELFT> void SymbolTableSection<ELFT>::addLocal(SymbolBody *B) {
   assert(!StrTabSec.isDynamic());
-  ++NumLocals;
   Symbols.push_back({B, StrTabSec.addString(B->getName())});
 }
 


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