[DebugInfo] Generate DWARF debug information for labels.

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.

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

Patch by Hsiangkai Wang.

llvm-svn: 337799

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp b/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
index 82e14dc13cb..580f682b9a6 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
@@ -190,8 +190,9 @@ void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
 
   // Calculate history for local variables.
   assert(DbgValues.empty() && "DbgValues map wasn't cleaned!");
-  calculateDbgValueHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
-                           DbgValues);
+  assert(DbgLabels.empty() && "DbgLabels map wasn't cleaned!");
+  calculateDbgEntityHistory(MF, Asm->MF->getSubtarget().getRegisterInfo(),
+                            DbgValues, DbgLabels);
   LLVM_DEBUG(DbgValues.dump());
 
   // Request labels for the full history.
@@ -229,6 +230,12 @@ void DebugHandlerBase::beginFunction(const MachineFunction *MF) {
     }
   }
 
+  // Ensure there is a symbol before DBG_LABEL.
+  for (const auto &I : DbgLabels) {
+    const MachineInstr *MI = I.second;
+    requestLabelBeforeInsn(MI);
+  }
+
   PrevInstLoc = DebugLoc();
   PrevLabel = Asm->getFunctionBegin();
   beginFunctionImpl(MF);
@@ -296,6 +303,7 @@ void DebugHandlerBase::endFunction(const MachineFunction *MF) {
   if (hasDebugInfo(MMI, MF))
     endFunctionImpl(MF);
   DbgValues.clear();
+  DbgLabels.clear();
   LabelsBeforeInsn.clear();
   LabelsAfterInsn.clear();
 }