[llvm] Skip over empty line table entries.

Summary:
This is similar to how addr2line handles consecutive entries with the
same address - pick the last one.

Reviewers: dblaikie, friss, JDevlieghere

Reviewed By: dblaikie

Subscribers: ormris, echristo, JDevlieghere, probinson, aprantl, hiraditya, rupprecht, jdoerfert, llvm-commits

Tags: #llvm, #debug-info

Differential Revision: https://reviews.llvm.org/D58952

llvm-svn: 355972

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
index a2c25248618..dee9428be29 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDebugLine.cpp
@@ -872,6 +872,13 @@ uint32_t DWARFDebugLine::LineTable::findRowInSeq(
   if (RowPos == LastRow) {
     return Seq.LastRowIndex - 1;
   }
+  // In some cases, e.g. first instruction in a function, the compiler generates
+  // two entries, both with the same address. We want the last one.
+  while (RowPos + 1 < LastRow &&
+         RowPos->Address.Address == (RowPos + 1)->Address.Address) {
+    ++RowPos;
+  }
+  assert(RowPos < LastRow);
   assert(Seq.SectionIndex == RowPos->Address.SectionIndex);
   uint32_t Index = Seq.FirstRowIndex + (RowPos - FirstRow);
   if (RowPos->Address.Address > Address.Address) {