[DebugInfo] Generate DWARF debug information for labels. (Fix leak problems)

There are two forms for label debug information in DWARF format.

1. Labels in a non-inlined function:

DW_TAG_label
  DW_AT_name
  DW_AT_decl_file
  DW_AT_decl_line
  DW_AT_low_pc

2. Labels in an inlined function:

DW_TAG_label
  DW_AT_abstract_origin
  DW_AT_low_pc

We will collect label information from DBG_LABEL. Before every DBG_LABEL,
we will generate a temporary symbol to denote the location of the label.
The symbol could be used to get DW_AT_low_pc afterwards. So, we create a
mapping between 'inlined label' and DBG_LABEL MachineInstr in DebugHandlerBase.
The DBG_LABEL in the mapping is used to query the symbol before it.

The AbstractLabels in DwarfCompileUnit is used to process labels in inlined
functions.

We also keep a mapping between scope and labels in DwarfFile to help to
generate correct tree structure of DIEs.

It also generates label debug information under global isel.

Differential Revision: https://reviews.llvm.org/D45556

llvm-svn: 340039
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 74f51cc..81bebdf 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -769,6 +769,17 @@
                                      DI.getVariable(), DI.getExpression());
     return true;
   }
+  case Intrinsic::dbg_label: {
+    const DbgLabelInst &DI = cast<DbgLabelInst>(CI);
+    assert(DI.getLabel() && "Missing label");
+
+    assert(DI.getLabel()->isValidLocationForIntrinsic(
+               MIRBuilder.getDebugLoc()) &&
+           "Expected inlined-at fields to agree");
+
+    MIRBuilder.buildDbgLabel(DI.getLabel());
+    return true;
+  }
   case Intrinsic::vaend:
     // No target I know of cares about va_end. Certainly no in-tree target
     // does. Simplest intrinsic ever!