Make findModulesDefiningSymbols modify its symbols argument so we can \

eliminate symbols defined by the archive efficiently

llvm-svn: 17976

2 files changed, 20 insertions, 6 deletions

diff --git a/llvm/include/llvm/Bytecode/Archive.h b/llvm/include/llvm/Bytecode/Archive.h
index 67615b3bef2..943d979cac3 100644
--- a/llvm/include/llvm/Bytecode/Archive.h
+++ b/llvm/include/llvm/Bytecode/Archive.h
@@ -396,11 +396,14 @@ class Archive {
     /// more than one symbol at a time. If \p symbols contains a list of 
     /// undefined symbols in some module, then calling this method is like 
     /// making one complete pass through the archive to resolve symbols but is
-    /// more efficient than looking at the individual members.
+    /// more efficient than looking at the individual members. Note that on 
+    /// exit, the symbols resolved by this method will be removed from \p
+    /// symbols to ensure they are not re-searched on a subsequent call. If
+    /// you need to retain the list of symbols, make a copy.
     /// @brief Look up multiple symbols in the archive.
     void findModulesDefiningSymbols(
-      const std::set<std::string>& symbols, ///< Symbols to be sought
-      std::set<ModuleProvider*>& modules    ///< The modules matching \p symbols
+      std::set<std::string>& symbols,     ///< Symbols to be sought
+      std::set<ModuleProvider*>& modules  ///< The modules matching \p symbols
     );
 
   /// @}
diff --git a/llvm/lib/Bytecode/Archive/ArchiveReader.cpp b/llvm/lib/Bytecode/Archive/ArchiveReader.cpp
index 615df2bf5f2..6f5b9d36edf 100644
--- a/llvm/lib/Bytecode/Archive/ArchiveReader.cpp
+++ b/llvm/lib/Bytecode/Archive/ArchiveReader.cpp
@@ -407,7 +407,7 @@ Archive::findModuleDefiningSymbol(const std::string& symbol) {
 // Look up multiple symbols in the symbol table and return a set of 
 // ModuleProviders that define those symbols.
 void
-Archive::findModulesDefiningSymbols(const std::set<std::string>& symbols,
+Archive::findModulesDefiningSymbols(std::set<std::string>& symbols,
                                     std::set<ModuleProvider*>& result)
 {
   assert(mapfile && base && "Can't findModulesDefiningSymbols on new archive");
@@ -462,11 +462,22 @@ Archive::findModulesDefiningSymbols(const std::set<std::string>& symbols,
   // At this point we have a valid symbol table (one way or another) so we 
   // just use it to quickly find the symbols requested.
 
-  for (std::set<std::string>::const_iterator I=symbols.begin(), 
-       E=symbols.end(); I != E; ++I) {
+  for (std::set<std::string>::iterator I=symbols.begin(), 
+       E=symbols.end(); I != E;) {
+    // See if this symbol exists
     ModuleProvider* mp = findModuleDefiningSymbol(*I);
     if (mp) {
+      // The symbol exists, insert the ModuleProvider into our result,
+      // duplicates wil be ignored
       result.insert(mp);
+
+      // Remove the symbol now that its been resolved, being careful to 
+      // not invalidate our iterator.
+      std::set<std::string>::iterator save = I;
+      ++I;
+      symbols.erase(save);
+    } else {
+      ++I;
     }
   }
 }