Allow epilogue_begin to be emitted when generating DWARF

We identify epilogue code by looking for instructions tagged
with FrameDestroy.

A function may have more than one epilogue, e.g., because of early
returns or code duplicated during optimization. We need only track
the current block, and emit epilogie_begin at most once per block.

We reduce the number of entries in the line table by combining
epilogue_begin with other flags instead of emitting a separate
entry just for epilogue_begin.

Reviewed By: dblaikie, aprantl

Differential Revision: https://reviews.llvm.org/D133376

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp b/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
index 1ad2362..2038952 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp
@@ -417,6 +417,7 @@ void DebugHandlerBase::endFunction(const MachineFunction *MF) {
 }
 
 void DebugHandlerBase::beginBasicBlockSection(const MachineBasicBlock &MBB) {
+  EpilogBeginBlock = nullptr;
   if (!MBB.isEntryBlock())
     PrevLabel = MBB.getSymbol();
 }