DwarfDebug: Check for null DebugLocs

`DL` might be null, so check for that before using accessors.  A WIP
patch to make `DIDescriptors` more strict fails otherwise.

As a bonus, I think the logic is easier to follow now (despite the extra
nesting depth).

llvm-svn: 232836

1 files changed, 15 insertions, 13 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index df5dd2e8333..e8e6c74e1ee 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -970,23 +970,25 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
   // Check if source location changes, but ignore DBG_VALUE locations.
   if (!MI->isDebugValue()) {
     DebugLoc DL = MI->getDebugLoc();
-    if (DL != PrevInstLoc && (!DL.isUnknown() || UnknownLocations)) {
-      unsigned Flags = 0;
-      PrevInstLoc = DL;
-      if (DL == PrologEndLoc) {
-        Flags |= DWARF2_FLAG_PROLOGUE_END;
-        PrologEndLoc = DebugLoc();
-        Flags |= DWARF2_FLAG_IS_STMT;
-      }
-      if (DL.getLine() !=
-          Asm->OutStreamer.getContext().getCurrentDwarfLoc().getLine())
-        Flags |= DWARF2_FLAG_IS_STMT;
-
+    if (DL != PrevInstLoc) {
       if (!DL.isUnknown()) {
+        unsigned Flags = 0;
+        PrevInstLoc = DL;
+        if (DL == PrologEndLoc) {
+          Flags |= DWARF2_FLAG_PROLOGUE_END;
+          PrologEndLoc = DebugLoc();
+          Flags |= DWARF2_FLAG_IS_STMT;
+        }
+        if (DL.getLine() !=
+            Asm->OutStreamer.getContext().getCurrentDwarfLoc().getLine())
+          Flags |= DWARF2_FLAG_IS_STMT;
+
         const MDNode *Scope = DL.getScope(Asm->MF->getFunction()->getContext());
         recordSourceLine(DL.getLine(), DL.getCol(), Scope, Flags);
-      } else
+      } else if (UnknownLocations) {
+        PrevInstLoc = DL;
         recordSourceLine(0, 0, nullptr, 0);
+      }
     }
   }