[DebugInfo] Introduce GNU macro extension entry encodings

[dstenb]

Summary

This is a preparatory patch for allowing the GNU .debug_macro extension,
which is a precursor to the DWARF 5 format, to be emitted by LLVM for
earlier DWARF versions.

The entries share the same encoding and behavior as in DWARF5; there are
just more entries in the DWARF 5 format. Therefore, we could have used
those existing DWARF 5 entries, but I think that explicitly referring to
the GNU macro variants makes the code more clear.

The defines that this patch introduces can be found in GCC in the dwarf2.h header:

https://gcc.gnu.org/git/?p=gcc.git;a=blob;
f=include/dwarf2.h;
h=0b6facfd4cf4c02320c7328114231b128ab42d5e;
hb=dccbf1e2a6e544f71b4a5795f0c79015db019fc3#l425

[dblaikie]

looks good - please include a link to the source of these values (literally the GCC source code, or some other reference) in the commit message and maybe in a comment near the "GNU .debug_macro extension." bit.

[SouraVX]

Do we really need this ?, Please have a look at https://sourceware.org/legacy-ml/gdb-patches/2017-02/msg00528.html
IMO, it would be unwise to commit it till the discussion thread in D82975 converges ?

[dstenb]

In D82972#2127215, @SouraVX wrote:

Do we really need this ?, Please have a look at https://sourceware.org/legacy-ml/gdb-patches/2017-02/msg00528.html
IMO, it would be unwise to commit it till the discussion thread in D82975 converges ?

As I write in the commit message this patch is not strictly needed, but I think it makes the code more clear.

I'll wait with this patch until we decide in D82975.

llvm/include/llvm/BinaryFormat/Dwarf.h

 /// DWARF v5 macro information entry type encodings.
 enum MacroEntryType {
 #define HANDLE_DW_MACRO(ID, NAME) DW_MACRO_##NAME = ID,
 #include "llvm/BinaryFormat/Dwarf.def"
   DW_MACRO_lo_user = 0xe0,
   DW_MACRO_hi_user = 0xff
 };
 
+/// GNU .debug_macro macro information entry type encodings.
+enum GnuMacroEntryType {
+#define HANDLE_DW_MACRO_GNU(ID, NAME) DW_MACRO_GNU_##NAME = ID,
+#include "llvm/BinaryFormat/Dwarf.def"
+  DW_MACRO_GNU_lo_user = 0xe0,
+  DW_MACRO_GNU_hi_user = 0xff
+};
+
 /// DWARF v5 range list entry encoding values.
 enum RnglistEntries {
 #define HANDLE_DW_RLE(ID, NAME) DW_RLE_##NAME = ID,
 #include "llvm/BinaryFormat/Dwarf.def"
 };
 
 /// DWARF v5 loc list entry encoding values.
 enum LoclistEntries {

llvm/include/llvm/BinaryFormat/Dwarf.def

 
 // TODO: Add other DW-based macros.
 #if !(                                                                         \
     defined HANDLE_DW_TAG || defined HANDLE_DW_AT || defined HANDLE_DW_FORM || \
     defined HANDLE_DW_OP || defined HANDLE_DW_LANG || defined HANDLE_DW_ATE || \
     defined HANDLE_DW_VIRTUALITY || defined HANDLE_DW_DEFAULTED ||             \
     defined HANDLE_DW_CC || defined HANDLE_DW_LNS || defined HANDLE_DW_LNE ||  \
     defined HANDLE_DW_LNCT || defined HANDLE_DW_MACRO ||                       \
-    defined HANDLE_MACRO_FLAG ||                                               \
+    defined HANDLE_DW_MACRO_GNU || defined HANDLE_MACRO_FLAG ||                \
     defined HANDLE_DW_RLE || defined HANDLE_DW_LLE ||                          \
     (defined HANDLE_DW_CFA && defined HANDLE_DW_CFA_PRED) ||                   \
     defined HANDLE_DW_APPLE_PROPERTY || defined HANDLE_DW_UT ||                \
     defined HANDLE_DWARF_SECTION || defined HANDLE_DW_IDX ||                   \
     defined HANDLE_DW_END || defined HANDLE_DW_SECT)
 #error "Missing macro definition of HANDLE_DW*"
 #endif
 

 #ifndef HANDLE_DW_LNCT
 #define HANDLE_DW_LNCT(ID, NAME)
 #endif
 
 #ifndef HANDLE_DW_MACRO
 #define HANDLE_DW_MACRO(ID, NAME)
 #endif
 
+#ifndef HANDLE_DW_MACRO_GNU
+#define HANDLE_DW_MACRO_GNU(ID, NAME)
+#endif
+
 #ifndef HANDLE_MACRO_FLAG
 #define HANDLE_MACRO_FLAG(ID, NAME)
 #endif
 
 #ifndef HANDLE_DW_RLE
 #define HANDLE_DW_RLE(ID, NAME)
 #endif
 

 HANDLE_DW_MACRO(0x06, undef_strp)
 HANDLE_DW_MACRO(0x07, import)
 HANDLE_DW_MACRO(0x08, define_sup)
 HANDLE_DW_MACRO(0x09, undef_sup)
 HANDLE_DW_MACRO(0x0a, import_sup)
 HANDLE_DW_MACRO(0x0b, define_strx)
 HANDLE_DW_MACRO(0x0c, undef_strx)
 
+// GNU .debug_macro extension.
+HANDLE_DW_MACRO_GNU(0x01, define)
+HANDLE_DW_MACRO_GNU(0x02, undef)
+HANDLE_DW_MACRO_GNU(0x03, start_file)
+HANDLE_DW_MACRO_GNU(0x04, end_file)
+HANDLE_DW_MACRO_GNU(0x05, define_indirect)
+HANDLE_DW_MACRO_GNU(0x06, undef_indirect)
+HANDLE_DW_MACRO_GNU(0x07, transparent_include)
+HANDLE_DW_MACRO_GNU(0x08, define_indirect_alt)
+HANDLE_DW_MACRO_GNU(0x09, undef_indirect_alt)
+HANDLE_DW_MACRO_GNU(0x0a, transparent_include_alt)
+
 // DWARF v5 Macro header flags.
 HANDLE_MACRO_FLAG(0x01, OFFSET_SIZE)
 HANDLE_MACRO_FLAG(0x02, DEBUG_LINE_OFFSET)
 HANDLE_MACRO_FLAG(0x04, OPCODE_OPERANDS_TABLE)
 
 // DWARF v5 Range List Entry encoding values.
 HANDLE_DW_RLE(0x00, end_of_list)
 HANDLE_DW_RLE(0x01, base_addressx)

 #undef HANDLE_DW_ATE
 #undef HANDLE_DW_VIRTUALITY
 #undef HANDLE_DW_DEFAULTED
 #undef HANDLE_DW_CC
 #undef HANDLE_DW_LNS
 #undef HANDLE_DW_LNE
 #undef HANDLE_DW_LNCT
 #undef HANDLE_DW_MACRO
+#undef HANDLE_DW_MACRO_GNU
 #undef HANDLE_MACRO_FLAG
 #undef HANDLE_DW_RLE
 #undef HANDLE_DW_LLE
 #undef HANDLE_DW_CFA
 #undef HANDLE_DW_CFA_PRED
 #undef HANDLE_DW_APPLE_PROPERTY
 #undef HANDLE_DW_UT
 #undef HANDLE_DWARF_SECTION
 #undef HANDLE_DW_IDX
 #undef HANDLE_DW_END
 #undef HANDLE_DW_SECT