Reapply r112091 and r111922, support for metadata linking, with a

fix: add a flag to MapValue and friends which indicates whether
any module-level mappings are being made. In the common case of
inlining, no module-level mappings are needed, so MapValue doesn't
need to examine non-function-local metadata, which can be very
expensive in the case of a large module with really deep metadata
(e.g. a large C++ program compiled with -g).

This flag is a little awkward; perhaps eventually it can be moved
into the ClonedCodeInfo class.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112190 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Linker/LinkModules.cpp

@@ -460,7 +460,8 @@ static void LinkNamedMDNodes(Module *Dest, Module *Src,
     // Add Src elements into Dest node.
     for (unsigned i = 0, e = SrcNMD->getNumOperands(); i != e; ++i) 
       DestNMD->addOperand(cast<MDNode>(MapValue(SrcNMD->getOperand(i),
-                                                ValueMap)));
+                                                ValueMap,
+                                                true)));
   }
 }
 
@@ -823,7 +824,7 @@ static bool LinkGlobalInits(Module *Dest, const Module *Src,
     if (SGV->hasInitializer()) {      // Only process initialized GV's
       // Figure out what the initializer looks like in the dest module...
       Constant *SInit =
-        cast<Constant>(MapValue(SGV->getInitializer(), ValueMap));
+        cast<Constant>(MapValue(SGV->getInitializer(), ValueMap, true));
       // Grab destination global variable or alias.
       GlobalValue *DGV = cast<GlobalValue>(ValueMap[SGV]->stripPointerCasts());
 
@@ -1005,12 +1006,30 @@ static bool LinkFunctionBody(Function *Dest, Function *Src,
   // the Source function as operands.  Loop through all of the operands of the
   // functions and patch them up to point to the local versions...
   //
+  // This is the same as RemapInstruction, except that it avoids remapping
+  // instruction and basic block operands.
+  //
   for (Function::iterator BB = Dest->begin(), BE = Dest->end(); BB != BE; ++BB)
-    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
+    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+      // Remap operands.
       for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
            OI != OE; ++OI)
         if (!isa<Instruction>(*OI) && !isa<BasicBlock>(*OI))
-          *OI = MapValue(*OI, ValueMap);
+          *OI = MapValue(*OI, ValueMap, true);
+
+      // Remap attached metadata.
+      SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
+      I->getAllMetadata(MDs);
+      for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
+           MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
+        Value *Old = MI->second;
+        if (!isa<Instruction>(Old) && !isa<BasicBlock>(Old)) {
+          Value *New = MapValue(Old, ValueMap, true);
+          if (New != Old) 
+            I->setMetadata(MI->first, cast<MDNode>(New));
+        }
+      }
+    }
 
   // There is no need to map the arguments anymore.
   for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end();