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

[mstorsjo]

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.

[llvmbot]

@llvm/pr-subscribers-platform-windows

@llvm/pr-subscribers-lld

Author: Martin Storsjö (mstorsjo)

Changes

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.

---

Full diff: https://github.com/llvm/llvm-project/pull/75172.diff

4 Files Affected:

• (modified) lld/COFF/Config.h (+2-2)
• (modified) lld/COFF/Driver.cpp (+3-3)
• (modified) lld/COFF/InputFiles.cpp (+2-2)
• (modified) lld/COFF/Writer.cpp (+1-1)

diff --git a/lld/COFF/Config.h b/lld/COFF/Config.h
index 24126f635a06f2..48c48cefe91d8e 100644
--- a/lld/COFF/Config.h
+++ b/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;
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 99c1a60735adc5..2eab745ad3b23c 100644
--- a/lld/COFF/Driver.cpp
+++ b/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
@@ -2028,9 +2029,8 @@ 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(
@@ -2049,7 +2049,7 @@ 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)) {
diff --git a/lld/COFF/InputFiles.cpp b/lld/COFF/InputFiles.cpp
index dd2e1419bb10a6..cd744800cb0dec 100644
--- a/lld/COFF/InputFiles.cpp
+++ b/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)
diff --git a/lld/COFF/Writer.cpp b/lld/COFF/Writer.cpp
index 7b1ff8071e2e3d..ec5d10ed990325 100644
--- a/lld/COFF/Writer.cpp
+++ b/lld/COFF/Writer.cpp
@@ -1376,7 +1376,7 @@ 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);

[mstorsjo]

The overall direction of the larger patchset that this belongs to, was presented/discussed in #74820.