Dwarf tools interpret line number table pc's as start boundries instead of end boundries.

runtime/vm/dwarf.cc

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/dwarf.h"
 
 #include "vm/code_descriptors.h"
 #include "vm/object_store.h"
 
 namespace dart {
@@ skipping 569 matching lines @@
 
           // 2. Update LNP line.
           TokenPosition pos = token_positions.Last();
           intptr_t line = pos.value();
           if (line != previous_line) {
             u1(DW_LNS_advance_line);
             sleb128(line - previous_line);
             previous_line = line;
           }
 
-          // 3. Update LNP pc.
+          // 3. Emit LNP row.
+          u1(DW_LNS_copy);
+
+          // 4. Update LNP pc.
           if (previous_code_index == -1) {
             // This variant is relocatable.
             u1(0);                  // This is an extended opcode
             u1(1 + sizeof(void*));  // that is 5 or 9 bytes long
             u1(DW_LNE_set_address);
             Print(FORM_ADDR " .Lcode%" Pd " + %" Pd "\n", i, current_pc_offset);
           } else {
             u1(DW_LNS_advance_pc);
             Print(".uleb128 .Lcode%" Pd " - .Lcode%" Pd " + %" Pd "\n", i,
                   previous_code_index, current_pc_offset - previous_pc_offset);
           }
           previous_code_index = i;
           previous_pc_offset = current_pc_offset;
-
-          // 4. Emit LNP row.
-          u1(DW_LNS_copy);
-
           break;
         }
         case CodeSourceMapBuilder::kPushFunction: {
           int32_t func_index = stream.Read<int32_t>();
           const Function& child_func = Function::Handle(
               zone_, Function::RawCast(functions.At(func_index)));
           function_stack.Add(&child_func);
           token_positions.Add(CodeSourceMapBuilder::kInitialPosition);
           break;
         }
@@ skipping 22 matching lines @@
   u1(0);  // This is an extended opcode
   u1(1);  // that is 1 byte long
   u1(DW_LNE_end_sequence);
 
   Print(".Lline_end:\n");
 }
 
 #endif  // DART_PRECOMPILER
 
 }  // namespace dart