Fix a crash in DwarfDebug::validThroughout.

The instruction it falls over on is an IMPLICT_DEF that also happens
to be the only instruction in its lexical scope. That LexicalScope has
never been created because its range is empty. This patch skips over
all meta-instructions instead of just DBG_VALUEs.

Thanks to David Blaikie for providing a testcase!

llvm-svn: 305853

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index d392e372863..f1b4d9f20ca 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1000,12 +1000,14 @@ static bool validThroughout(LexicalScopes &LScopes,
     if (Pred->getFlag(MachineInstr::FrameSetup))
       break;
     auto PredDL = Pred->getDebugLoc();
-    if (!PredDL || Pred->isDebugValue())
+    if (!PredDL || Pred->isMetaInstruction())
       continue;
     // Check whether the instruction preceding the DBG_VALUE is in the same
     // (sub)scope as the DBG_VALUE.
-    if (DL->getScope() == PredDL->getScope() ||
-        LScope->dominates(LScopes.findLexicalScope(PredDL)))
+    if (DL->getScope() == PredDL->getScope())
+      return false;
+    auto *PredScope = LScopes.findLexicalScope(PredDL);
+    if (!PredScope || LScope->dominates(PredScope))
       return false;
   }