[DebugInfo] Explicitly permit addr_size = 0x02 when parsing DWARF data

[atrosinenko]

Summary

Current LLVM implementation uses MCAsmInfo::CodePointerSize as addr_size when emitting the DWARF data. llvm-dwarfdump, on the other hand, handles addr_sizes of 4 and 8 properly and considers all other sizes as an error. This works for most of mainline targets except for MSP430 and AVR.

msp430-gcc v8.3.1 emits DWARF32 with addr_size = 4 (DWARF32 does not imply addr_size = 4, 32 refers to internal offset width of 4 bytes) that is handled by llvm-dwarfdump already. Still, emitting 2-byte target pointers on MSP430 seems correct as well (but not for MSP430X that is supported by msp430-gcc but not by LLVM and has 20-bit address space).

This patch make it possible for MSP430 debug info support to be tested with llvm-dwarfdump.

[atrosinenko]

Unit test: fix backslash on Windows

[probinson]

LGTM

In a .test file, you don't actually need the comment markers. They're not harmful either, so up to you whether to leave them in.
Some people prefer that commentary and action lines (REQUIRES, CHECK, etc) have different comment markings, just for readability.

[atrosinenko]

Thank you!

llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h

public:
   std::vector<DILocal>
   getLocalsForAddress(object::SectionedAddress Address) override;
 
   bool isLittleEndian() const { return DObj->isLittleEndian(); }
   static bool isSupportedVersion(unsigned version) {
     return version == 2 || version == 3 || version == 4 || version == 5;
   }
 
+  static bool isAddressSizeSupported(unsigned AddressSize) {
+    return AddressSize == 2 || AddressSize == 4 || AddressSize == 8;
+  }
+
   std::shared_ptr<DWARFContext> getDWOContext(StringRef AbsolutePath);
 
   const MCRegisterInfo *getRegisterInfo() const { return RegInfo.get(); }
 
   function_ref<void(Error)> getRecoverableErrorHandler() {
     return RecoverableErrorHandler;
   }
 

llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp

bool DWARFUnitHeader::extract(DWARFContext &Context,
   // the end of the current unit.
   bool TypeOffsetOK =
       !isTypeUnit()
           ? true
           : TypeOffset >= Size &&
                 TypeOffset < getLength() + getUnitLengthFieldByteSize();
   bool LengthOK = debug_info.isValidOffset(getNextUnitOffset() - 1);
   bool VersionOK = DWARFContext::isSupportedVersion(getVersion());
-  bool AddrSizeOK = getAddressByteSize() == 4 || getAddressByteSize() == 8;
+  bool AddrSizeOK = DWARFContext::isAddressSizeSupported(getAddressByteSize());
 
   if (!LengthOK || !VersionOK || !AddrSizeOK || !TypeOffsetOK)
     return false;
 
   // Keep track of the highest DWARF version we encounter across all units.
   Context.setMaxVersionIfGreater(getVersion());
   return true;
 }

llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp

if (Version >= 5) {
     AddrSize = DebugInfoData.getU8(Offset);
   }
 
   if (!DCtx.getDebugAbbrev()->getAbbreviationDeclarationSet(AbbrOffset))
     ValidAbbrevOffset = false;
 
   ValidLength = DebugInfoData.isValidOffset(OffsetStart + Length + 3);
   ValidVersion = DWARFContext::isSupportedVersion(Version);
-  ValidAddrSize = AddrSize == 4 || AddrSize == 8;
+  ValidAddrSize = DWARFContext::isAddressSizeSupported(AddrSize);
   if (!ValidLength || !ValidVersion || !ValidAddrSize || !ValidAbbrevOffset ||
       !ValidType) {
     Success = false;
     error() << format("Units[%d] - start offset: 0x%08" PRIx64 " \n", UnitIndex,
                       OffsetStart);
     if (!ValidLength)
       note() << "The length for this unit is too "
                 "large for the .debug_info provided.\n";

llvm/test/DebugInfo/dwarfdump-16bit-addr.test

+; Test that llvm-dwarfdump can handle DWARF32 v3 with addr_size = 0x02
+; Input object file was produced from source containing just "int x;" with
+;   clang -target avr -gdwarf-3 -c dwarfdump-16bit-addr.c
+
+; REQUIRES: avr-registered-target
+; RUN: llvm-dwarfdump --debug-info %S/Inputs/dwarfdump-16bit-addr.o | FileCheck %s
+; RUN: llvm-dwarfdump --verify %S/Inputs/dwarfdump-16bit-addr.o
+
+; CHECK: Inputs/dwarfdump-16bit-addr.o:  file format elf32-avr
+
+; CHECK: .debug_info contents:
+; CHECK: 0x00000000: Compile Unit: length = 0x00000032, format = DWARF32, version = 0x0003, abbr_offset = 0x0000, addr_size = 0x02 (next unit at 0x00000036)
+
+; CHECK: 0x0000000b: DW_TAG_compile_unit
+; CHECK:               DW_AT_producer    ("clang version 10.0.0-4ubuntu1 ")
+; CHECK:               DW_AT_language    (DW_LANG_C99)
+; CHECK:               DW_AT_name        ("dwarfdump-16bit-addr.c")
+; CHECK:               DW_AT_stmt_list   (0x00000000)
+; CHECK:               DW_AT_comp_dir    ("/tmp")
+
+; CHECK: 0x0000001e:   DW_TAG_variable
+; CHECK:                 DW_AT_name      ("x")
+; CHECK:                 DW_AT_type      (0x0000002e "int")
+; CHECK:                 DW_AT_external  (0x01)
+; CHECK:                 DW_AT_decl_file ("/tmp{{[/\\]}}dwarfdump-16bit-addr.c")
+; CHECK:                 DW_AT_decl_line (1)
+; CHECK:                 DW_AT_location  (DW_OP_addr 0x0)
+
+; CHECK: 0x0000002e:   DW_TAG_base_type
+; CHECK:                 DW_AT_name      ("int")
+; CHECK:                 DW_AT_encoding  (DW_ATE_signed)
+; CHECK:                 DW_AT_byte_size (0x02)
+
+; CHECK: 0x00000035:   NULL