ldc-developers · kinke · Aug 11, 2020 · Aug 4, 2020
diff --git a/driver/cl_options.cpp b/driver/cl_options.cpp
@@ -183,6 +183,10 @@ static cl::opt<unsigned char, true> debugInfo(
         clEnumValN(3, "gline-tables-only", "Add line tables only")),
     cl::location(global.params.symdebug), cl::init(0));
 
+cl::opt<bool> emitDwarfDebugInfo(
+    "gdwarf", cl::ZeroOrMore,
+    cl::desc("Emit DWARF debuginfo (instead of CodeView) for MSVC targets"));
+
 cl::opt<bool> noAsm("noasm", cl::desc("Disallow use of inline assembler"),
                     cl::ZeroOrMore);
 

diff --git a/driver/cl_options.h b/driver/cl_options.h
@@ -45,6 +45,7 @@ extern cl::list<std::string> fileList;
 extern cl::list<std::string> runargs;
 extern cl::opt<bool> invokedByLDMD;
 extern cl::opt<bool> compileOnly;
+extern cl::opt<bool> emitDwarfDebugInfo;
 extern cl::opt<bool> noAsm;
 extern cl::opt<bool> dontWriteObj;
 extern cl::opt<std::string> objectFile;

diff --git a/driver/linker.cpp b/driver/linker.cpp
@@ -169,7 +169,17 @@ static std::vector<std::string> getDefaultLibNames() {
 
 //////////////////////////////////////////////////////////////////////////////
 
-bool useInternalLLDForLinking() { return linkInternally; }
+bool useInternalLLDForLinking() {
+  return linkInternally
+#if LDC_WITH_LLD
+         ||
+         // DWARF debuginfos for MSVC require LLD
+         (opts::emitDwarfDebugInfo && linkInternally.getNumOccurrences() == 0 &&
+          opts::linker.empty() && !opts::isUsingLTO() &&
+          global.params.targetTriple->isWindowsMSVCEnvironment())
+#endif
+      ;
+}
 
 cl::boolOrDefault linkFullyStatic() { return staticFlag; }
 

diff --git a/driver/main.cpp b/driver/main.cpp
@@ -1045,6 +1045,11 @@ int cppmain() {
       global.obj_ext = {3, "obj"};
   }
 
+  // -gdwarf implies -g if not specified explicitly
+  if (opts::emitDwarfDebugInfo && global.params.symdebug == 0) {
+    global.params.symdebug = 1;
+  }
+
   // allocate the target abi
   gABI = TargetABI::getTarget();
 

diff --git a/gen/dibuilder.cpp b/gen/dibuilder.cpp
@@ -101,12 +101,11 @@ bool DIBuilder::mustEmitLocationsDebugInfo() {
 
 DIBuilder::DIBuilder(IRState *const IR)
     : IR(IR), DBuilder(IR->module), CUNode(nullptr),
-      isTargetMSVC(global.params.targetTriple->isWindowsMSVCEnvironment()),
-      isTargetMSVCx64(isTargetMSVC &&
-                      global.params.targetTriple->isArch64Bit()),
+      emitCodeView(!opts::emitDwarfDebugInfo &&
+                   global.params.targetTriple->isWindowsMSVCEnvironment()),
       // like clang, don't emit any column infos for CodeView by default
       // (https://reviews.llvm.org/D23720)
-      emitColumnInfo(opts::getFlagOrDefault(::emitColumnInfo, !isTargetMSVC)) {}
+      emitColumnInfo(opts::getFlagOrDefault(::emitColumnInfo, !emitCodeView)) {}
 
 llvm::LLVMContext &DIBuilder::getContext() { return IR->context(); }
 
@@ -244,7 +243,7 @@ DIType DIBuilder::CreateBasicType(Type *type) {
     Encoding = DW_ATE_boolean;
     break;
   case Tchar:
-    if (isTargetMSVC) {
+    if (emitCodeView) {
       // VS debugger does not support DW_ATE_UTF for char
       Encoding = DW_ATE_unsigned_char;
       break;
@@ -255,7 +254,7 @@ DIType DIBuilder::CreateBasicType(Type *type) {
     Encoding = DW_ATE_UTF;
     break;
   case Tint8:
-    if (isTargetMSVC) {
+    if (emitCodeView) {
       // VS debugger does not support DW_ATE_signed for 8-bit
       Encoding = DW_ATE_signed_char;
       break;
@@ -268,7 +267,7 @@ DIType DIBuilder::CreateBasicType(Type *type) {
     Encoding = DW_ATE_signed;
     break;
   case Tuns8:
-    if (isTargetMSVC) {
+    if (emitCodeView) {
       // VS debugger does not support DW_ATE_unsigned for 8-bit
       Encoding = DW_ATE_unsigned_char;
       break;
@@ -288,7 +287,7 @@ DIType DIBuilder::CreateBasicType(Type *type) {
   case Timaginary32:
   case Timaginary64:
   case Timaginary80:
-    if (isTargetMSVC) {
+    if (emitCodeView) {
       // DW_ATE_imaginary_float not supported by the LLVM DWARF->CodeView
       // conversion
       Encoding = DW_ATE_float;
@@ -299,7 +298,7 @@ DIType DIBuilder::CreateBasicType(Type *type) {
   case Tcomplex32:
   case Tcomplex64:
   case Tcomplex80:
-    if (isTargetMSVC) {
+    if (emitCodeView) {
       // DW_ATE_complex_float not supported by the LLVM DWARF->CodeView
       // conversion
       return CreateComplexType(t);
@@ -890,11 +889,22 @@ void DIBuilder::EmitCompileUnit(Module *m) {
   auto producerName =
       std::string("LDC ") + ldc_version + " (LLVM " + llvm_version + ")";
 
-  if (isTargetMSVC)
+  if (emitCodeView) {
     IR->module.addModuleFlag(llvm::Module::Warning, "CodeView", 1);
-  else if (global.params.dwarfVersion > 0)
-    IR->module.addModuleFlag(llvm::Module::Warning, "Dwarf Version",
-                             global.params.dwarfVersion);
+  } else {
+    unsigned dwarfVersion = global.params.dwarfVersion;
+    if (dwarfVersion == 0 &&
+        global.params.targetTriple->isWindowsMSVCEnvironment()) {
+      // clang 10 defaults to v4
+      dwarfVersion = 4;
+    }
+
+    if (dwarfVersion > 0) {
+      IR->module.addModuleFlag(llvm::Module::Warning, "Dwarf Version",
+                               dwarfVersion);
+    }
+  }
+
   // Metadata without a correct version will be stripped by UpgradeDebugInfo.
   IR->module.addModuleFlag(llvm::Module::Warning, "Debug Info Version",
                            llvm::DEBUG_METADATA_VERSION);
@@ -974,7 +984,7 @@ DISubprogram DIBuilder::EmitSubProgram(FuncDeclaration *fd) {
   DIScope scope = nullptr;
   llvm::StringRef name;
   // FIXME: work around apparent LLVM CodeView bug wrt. nested functions
-  if (isTargetMSVC && fd->toParent2()->isFuncDeclaration()) {
+  if (emitCodeView && fd->toParent2()->isFuncDeclaration()) {
     // emit into module & use fully qualified name
     scope = GetCU();
     name = fd->toPrettyChars(true);
@@ -1241,7 +1251,8 @@ void DIBuilder::EmitLocalVariable(llvm::Value *ll, VarDeclaration *vd,
 
   // For MSVC x64, some by-value parameters need to be declared as DI locals to
   // work around garbage for both cdb and VS debuggers.
-  if (isParameter && !forceAsLocal && isTargetMSVCx64 && !isRefOrOut) {
+  if (emitCodeView && isParameter && !forceAsLocal && !isRefOrOut &&
+      global.params.targetTriple->isArch64Bit()) {
     // 1) params rewritten by IndirectByvalRewrite
     if (isaArgument(ll) && addr.empty()) {
       forceAsLocal = true;

diff --git a/gen/dibuilder.h b/gen/dibuilder.h
@@ -63,8 +63,7 @@ class DIBuilder {
 
   DICompileUnit CUNode;
 
-  const bool isTargetMSVC;
-  const bool isTargetMSVCx64;
+  const bool emitCodeView;
   const bool emitColumnInfo;
 
   llvm::DenseMap<Declaration*, llvm::TypedTrackingMDRef<llvm::MDNode>> StaticDataMemberCache;

diff --git a/tests/debuginfo/msvc_dwarf.d b/tests/debuginfo/msvc_dwarf.d
@@ -0,0 +1,16 @@
+// REQUIRES: Windows
+
+// RUN: %ldc -gdwarf -of=%t.exe %s 2> %t_stderr.log
+// RUN: FileCheck %s < %t_stderr.log
+// CHECK: lld-link: warning: section name .debug_info is longer than 8 characters and will use a non-standard string table
+
+int foo(int p)
+{
+    auto r = 2 * p;
+    return r;
+}
+
+void main()
+{
+    foo(123);
+}