1. Add a pass to fold debug label instructions so a debug info client can detect

empty ranges.

2. Reorg how MachineDebugInfo maintains changes to debug labels.

3. Have dwarf writer use debug label info to simplify scopes and source line
coorespondence.

4. Revert the merging of compile units until I can get the bugs ironed out.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31507 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LLVMTargetMachine.cpp

@@ -66,6 +66,9 @@ bool LLVMTargetMachine::addPassesToEmitFile(FunctionPassManager &PM,
   // Branch folding must be run after regalloc and prolog/epilog insertion.
   if (!Fast)
     PM.add(createBranchFoldingPass());
+    
+  // Fold redundant debug labels.
+  PM.add(createDebugLabelFoldingPass());
   
   if (PrintMachineCode)  // Print the register-allocated code
     PM.add(createMachineFunctionPrinterPass(&std::cerr));