[LLD] [COFF] Rewrite the config flags for dwarf debug info or symtab. NFC. (#75172)

This shouldn't have any user visible effect, but makes the logic within
the linker implementation more explicit.

Note how DWARF debug info sections were retained even if enabling a link
with PDB info only; that behaviour is preserved.

Author: mstorsjo

lld/COFF/Config.h

@@ -130,9 +130,9 @@ struct Configuration {
   bool forceMultipleRes = false;
   bool forceUnresolved = false;
   bool debug = false;
-  bool debugDwarf = false;
+  bool includeDwarfChunks = false;
   bool debugGHashes = false;
-  bool debugSymtab = false;
+  bool writeSymtab = false;
   bool driver = false;
   bool driverUponly = false;
   bool driverWdm = false;

lld/COFF/Driver.cpp

@@ -1653,6 +1653,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
       debug == DebugKind::GHash || debug == DebugKind::NoGHash) {
     config->debug = true;
     config->incremental = true;
+    config->includeDwarfChunks = true;
   }
 
   // Handle /demangle
@@ -2029,9 +2030,8 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
     parseSwaprun(arg->getValue());
   config->terminalServerAware =
       !config->dll && args.hasFlag(OPT_tsaware, OPT_tsaware_no, true);
-  config->debugDwarf = debug == DebugKind::Dwarf;
   config->debugGHashes = debug == DebugKind::GHash || debug == DebugKind::Full;
-  config->debugSymtab = debug == DebugKind::Symtab;
+  config->writeSymtab = debug == DebugKind::Dwarf || debug == DebugKind::Symtab;
   config->autoImport =
       args.hasFlag(OPT_auto_import, OPT_auto_import_no, config->mingw);
   config->pseudoRelocs = args.hasFlag(
@@ -2050,7 +2050,7 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
 
   // Don't warn about long section names, such as .debug_info, for mingw or
   // when -debug:dwarf is requested.
-  if (config->mingw || config->debugDwarf)
+  if (config->mingw || debug == DebugKind::Dwarf)
     config->warnLongSectionNames = false;
 
   if (config->incremental && args.hasArg(OPT_profile)) {

lld/COFF/InputFiles.cpp

@@ -236,8 +236,8 @@ SectionChunk *ObjFile::readSection(uint32_t sectionNumber,
   // CodeView needs linker support. We need to interpret debug info,
   // and then write it to a separate .pdb file.
 
-  // Ignore DWARF debug info unless /debug is given.
-  if (!ctx.config.debug && name.starts_with(".debug_"))
+  // Ignore DWARF debug info unless requested to be included.
+  if (!ctx.config.includeDwarfChunks && name.starts_with(".debug_"))
     return nullptr;
 
   if (sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)

lld/COFF/Writer.cpp

@@ -1379,7 +1379,7 @@ void Writer::createSymbolAndStringTable() {
     sec->setStringTableOff(addEntryToStringTable(sec->name));
   }
 
-  if (ctx.config.debugDwarf || ctx.config.debugSymtab) {
+  if (ctx.config.writeSymtab) {
     for (ObjFile *file : ctx.objFileInstances) {
       for (Symbol *b : file->getSymbols()) {
         auto *d = dyn_cast_or_null<Defined>(b);