[dsymutil] Accept DWARF4 line tables.

[JDevlieghere]

Summary

This patch removes the hard-coded check for DWARFv2 line tables. Now
dsymutil accepts line tables for DWARF versions 2 to 5 (inclusive).

[probinson]

tools/dsymutil/DwarfLinker.cpp

3235

This calculation is incorrect for v5, which has an extra 2 bytes of information before the header_length field. Your choice whether to fix the calculation or restrict dsymutil to no higher than v4.

[JDevlieghere]

tools/dsymutil/DwarfLinker.cpp

3235

Thanks Paul! I will update the calculation.

[JDevlieghere]

• Fix calculation and add test for DWARFv5

[aprantl]

tools/dsymutil/DwarfLinker.cpp

3247

Comment where the extra two bytes come from?

[probinson]

Awesome. LGTM.

test/tools/dsymutil/X86/dwarf4-linetable.test

+# RUN: llvm-dsymutil -f -oso-prepend-path=%p/../Inputs/ -y %s -o - | llvm-dwarfdump -debug-line - | FileCheck %s
+
+# Source:
+#   int main() {
+#     return 0;
+#   }
+# Compile with:
+#   clang -gdwarf-4 dwarf4.c -c -o dwarf4.o
+
+---
+triple:          'x86_64-apple-darwin'
+objects:
+  - filename:        dwarf4.o
+    timestamp:       1513021112
+    symbols:
+      - { sym: _main, objAddr: 0x0000000000000000, binAddr: 0x0000000100000FA0, size: 0x0000000F }
+...
+
+# CHECK: .debug_line contents:
+# CHECK: debug_line
+# CHECK: Line table prologue:
+# CHECK: total_length:
+# CHECK: version: 4

tools/dsymutil/DwarfLinker.cpp

for (auto &Row : LineTable.Rows) {
     Row.Address += CurrRange.value();
     Seq.emplace_back(Row);
 
     if (Row.EndSequence)
       insertLineSequence(Seq, NewRows);
   }
 
   // Finished extracting, now emit the line tables.
   uint32_t PrologueEnd = *StmtList + 10 + LineTable.Prologue.PrologueLength;
   // FIXME: LLVM hardcodes it's prologue values. We just copy the
   // prologue over and that works because we act as both producer and
   // consumer. It would be nicer to have a real configurable line
   // table emitter.
-  if (LineTable.Prologue.getVersion() != 2 ||
+  if (LineTable.Prologue.getVersion() < 2 ||
+      LineTable.Prologue.getVersion() > 5 ||
       LineTable.Prologue.DefaultIsStmt != DWARF2_LINE_DEFAULT_IS_STMT ||
       LineTable.Prologue.OpcodeBase > 13)
     reportWarning("line table parameters mismatch. Cannot emit.");
   else {
     StringRef LineData = OrigDwarf.getDWARFObj().getLineSection().Data;
     MCDwarfLineTableParams Params;
     Params.DWARF2LineOpcodeBase = LineTable.Prologue.OpcodeBase;
     Params.DWARF2LineBase = LineTable.Prologue.LineBase;
     Params.DWARF2LineRange = LineTable.Prologue.LineRange;
     Streamer->emitLineTableForUnit(Params,
                                    LineData.slice(*StmtList + 4, PrologueEnd),
                                    LineTable.Prologue.MinInstLength, NewRows,
                                    Unit.getOrigUnit().getAddressByteSize());
   }