[AsmPrinter] Collapse .loc 0 0 directives

Currently we do not always collapse subsequent .loc 0 0 directives. The
reason is that we were checking for a PrevInstLoc which is not set when
we emit a line-0 record. We should only check the LastAsmLine, which
seems to be created exactly for this purpose.

  // When we emit a line-0 record, we don't update PrevInstLoc; so look at
  // the last line number actually emitted, to see if it was line 0.
  unsigned LastAsmLine =
    Asm->OutStreamer->getContext().getCurrentDwarfLoc().getLine();

Differential revision: https://reviews.llvm.org/D56767

llvm-svn: 351395

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 1de2ffb6cfa..2dc94614803 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1489,7 +1489,7 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
   // We have an explicit location, different from the previous location.
   // Don't repeat a line-0 record, but otherwise emit the new location.
   // (The new location might be an explicit line 0, which we do emit.)
-  if (PrevInstLoc && DL.getLine() == 0 && LastAsmLine == 0)
+  if (DL.getLine() == 0 && LastAsmLine == 0)
     return;
   unsigned Flags = 0;
   if (DL == PrologEndLoc) {