Fix debug info in absense of DIFinder

[hiraditya]

Summary

w.r.t discussion, the correct fix for debug info in absense of DIFinder

http://lists.llvm.org/pipermail/llvm-dev/2017-June/114390.html

[JDevlieghere]

Can you add a test?

[aprantl]

lib/Transforms/Utils/CloneFunction.cpp

55

Can you add a comment explaining what this does?

[hiraditya]

My testcase got fixed just with https://reviews.llvm.org/D45926. I'm wondering if this patch is still a good idea.

[hiraditya]

Not required.

lib/Transforms/Utils/CloneFunction.cpp

BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap,
 
   bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
   Module *TheModule = F ? F->getParent() : nullptr;
 
   // Loop over all instructions, and copy them over.
   for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
        II != IE; ++II) {
 
+    if (!DIFinder && II->getDebugLoc())
+      VMap.MD()[II->getDebugLoc()].reset(II->getDebugLoc());
     if (DIFinder && TheModule) {
       if (auto *DDI = dyn_cast<DbgDeclareInst>(II))
         DIFinder->processDeclare(*TheModule, DDI);
       else if (auto *DVI = dyn_cast<DbgValueInst>(II))
         DIFinder->processValue(*TheModule, DVI);
 
       if (auto DbgLoc = II->getDebugLoc())
         DIFinder->processLocation(*TheModule, DbgLoc.get());