Make the DWARF version emitted by the Swift compiler configurable.

Previously it was hardcoded to version 4 on all platforms.
This patch introduces a driver and frontend option -dwarf-version to configure it if needed.

Author: adrian-prantl

include/swift/AST/IRGenOptions.h

@@ -237,7 +237,7 @@ class IRGenOptions {
   std::string DebugCompilationDir;
 
   /// The DWARF version of debug info.
-  unsigned DWARFVersion;
+  uint8_t DWARFVersion = 4;
 
   /// The command line string that is to be stored in the debug info.
   std::string DebugFlags;
@@ -512,8 +512,7 @@ class IRGenOptions {
   bool EmitCASIDFile;
 
   IRGenOptions()
-      : DWARFVersion(2),
-        OutputKind(IRGenOutputKind::LLVMAssemblyAfterOptimization),
+      : OutputKind(IRGenOutputKind::LLVMAssemblyAfterOptimization),
         Verify(true), OptMode(OptimizationMode::NotSet),
         Sanitizers(OptionSet<SanitizerKind>()),
         SanitizersWithRecoveryInstrumentation(OptionSet<SanitizerKind>()),

include/swift/Driver/Driver.h

@@ -125,6 +125,9 @@ class OutputInfo {
   /// What kind of debug info to generate.
   IRGenDebugInfoFormat DebugInfoFormat = IRGenDebugInfoFormat::None;
 
+  /// DWARF output format version number.
+  std::optional<uint8_t> DWARFVersion;
+
   /// Whether or not the driver should generate a module.
   bool ShouldGenerateModule = false;
 

include/swift/Option/Options.td

@@ -991,8 +991,8 @@ def gdwarf_types : Flag<["-"], "gdwarf-types">,
   Group<g_Group>, Flags<[FrontendOption]>,
   HelpText<"Emit full DWARF type info.">;
 def debug_prefix_map : Separate<["-"], "debug-prefix-map">,
-    Flags<[FrontendOption]>,
-    HelpText<"Remap source paths in debug info">, MetaVarName<"<prefix=replacement>">;
+  Flags<[FrontendOption]>,
+  HelpText<"Remap source paths in debug info">, MetaVarName<"<prefix=replacement>">;
 def coverage_prefix_map : Separate<["-"], "coverage-prefix-map">,
   Flags<[FrontendOption]>,
   HelpText<"Remap source paths in coverage info">, MetaVarName<"<prefix=replacement>">;
@@ -1007,6 +1007,10 @@ def file_compilation_dir : Separate<["-"], "file-compilation-dir">,
 def debug_info_format : Joined<["-"], "debug-info-format=">,
   Flags<[FrontendOption]>,
   HelpText<"Specify the debug info format type to either 'dwarf' or 'codeview'">;
+def dwarf_version : Joined<["-"], "dwarf-version=">,
+  Flags<[FrontendOption]>,
+  HelpText<"DWARF debug info version to produce if requested">,
+  MetaVarName<"<version>">;
 
 def prefix_serialized_debugging_options : Flag<["-"], "prefix-serialized-debugging-options">,
   Flags<[FrontendOption]>,

lib/Driver/DarwinToolChains.cpp

@@ -625,6 +625,28 @@ toolchains::Darwin::addDeploymentTargetArgs(ArgStringList &Arguments,
   }
 }
 
+static unsigned getDWARFVersionForTriple(const llvm::Triple &triple) {
+  llvm::VersionTuple osVersion;
+  const DarwinPlatformKind kind = getDarwinPlatformKind(triple);
+  switch (kind) {
+  case DarwinPlatformKind::MacOS:
+    triple.getMacOSXVersion(osVersion);
+    if (osVersion < llvm::VersionTuple(10, 11))
+      return 2;
+    return 4;
+  case DarwinPlatformKind::IPhoneOSSimulator:
+  case DarwinPlatformKind::IPhoneOS:
+  case DarwinPlatformKind::TvOS:
+  case DarwinPlatformKind::TvOSSimulator:
+    osVersion = triple.getiOSVersion();
+    if (osVersion < llvm::VersionTuple(9))
+      return 2;
+    return 4;
+  default:
+    return 4;
+  }
+}
+
 void toolchains::Darwin::addCommonFrontendArgs(
     const OutputInfo &OI, const CommandOutput &output,
     const llvm::opt::ArgList &inputArgs,
@@ -643,6 +665,16 @@ void toolchains::Darwin::addCommonFrontendArgs(
           inputArgs.MakeArgString(variantSDKVersion->getAsString()));
     }
   }
+  std::string dwarfVersion;
+  {
+    llvm::raw_string_ostream os(dwarfVersion);
+    os << "-dwarf-version=";
+    if (OI.DWARFVersion)
+      os << *OI.DWARFVersion;
+    else
+      os << getDWARFVersionForTriple(getTriple());
+  }
+  arguments.push_back(inputArgs.MakeArgString(dwarfVersion));
 }
 
 /// Add the frontend arguments needed to find external plugins in standard

lib/Driver/Driver.cpp

@@ -1685,6 +1685,16 @@ void Driver::buildOutputInfo(const ToolChain &TC, const DerivedArgList &Args,
                      : "-gdwarf_types");
   }
 
+  if (const Arg *A = Args.getLastArg(options::OPT_dwarf_version)) {
+    unsigned vers;
+    if (!StringRef(A->getValue()).getAsInteger(10, vers) && vers >= 2 &&
+        vers <= 5)
+      OI.DWARFVersion = vers;
+    else
+      Diags.diagnose(SourceLoc(), diag::error_invalid_arg_value,
+                     A->getAsString(Args), A->getValue());
+  }
+
   if (Args.hasArg(options::OPT_emit_module, options::OPT_emit_module_path)) {
     // The user has requested a module, so generate one and treat it as
     // top-level output.

lib/Driver/ToolChains.cpp

@@ -261,6 +261,7 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
   inputArgs.AddLastArg(arguments, options::OPT_enable_private_imports);
   inputArgs.AddLastArg(arguments, options::OPT_g_Group);
   inputArgs.AddLastArg(arguments, options::OPT_debug_info_format);
+  inputArgs.AddLastArg(arguments, options::OPT_dwarf_version);
   inputArgs.AddLastArg(arguments, options::OPT_import_underlying_module);
   inputArgs.AddLastArg(arguments, options::OPT_module_cache_path);
   inputArgs.AddLastArg(arguments, options::OPT_module_link_name);

lib/Frontend/CompilerInvocation.cpp

@@ -2472,7 +2472,6 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
       Opts.DebugCompilationDir = std::string(cwd.str());
     }
   }
-
   if (const Arg *A = Args.getLastArg(options::OPT_debug_info_format)) {
     if (A->containsValue("dwarf"))
       Opts.DebugInfoFormat = IRGenDebugInfoFormat::DWARF;
@@ -2502,6 +2501,16 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
                      : "-gdwarf_types");
   }
 
+  if (auto A = Args.getLastArg(OPT_dwarf_version)) {
+    unsigned vers;
+    if (!StringRef(A->getValue()).getAsInteger(10, vers) && vers >= 2 &&
+        vers <= 5)
+      Opts.DWARFVersion = vers;
+    else
+      Diags.diagnose(SourceLoc(), diag::error_invalid_arg_value,
+                     A->getAsString(Args), A->getValue());
+  }
+
   for (auto A : Args.getAllArgValues(options::OPT_file_prefix_map)) {
     auto SplitMap = StringRef(A).split('=');
     Opts.FilePrefixMap.addMapping(SplitMap.first, SplitMap.second);

lib/FrontendTool/FrontendTool.cpp

@@ -2240,6 +2240,10 @@ int swift::performFrontend(ArrayRef<const char *> Args,
              trace.emplace(*buffer);
            });
 
+  // Setting DWARF Version based on frontend options.
+  IRGenOptions &IRGenOpts = Invocation.getIRGenOptions();
+  IRGenOpts.DWARFVersion = IRGenOpts.DWARFVersion;
+
   // The compiler invocation is now fully configured; notify our observer.
   if (observer) {
     observer->parsedArgs(Invocation);

test/Driver/options.swift

@@ -116,6 +116,14 @@
 // RUN: not %swiftc_driver -debug-info-format=codeview %s 2>&1 | %FileCheck -check-prefix MISSING_OPTION_G_ERROR %s
 // MISSING_OPTION_G_ERROR: error: option '-debug-info-format={{.*}}' is missing a required argument (-g)
 
+// RUN: %swift_driver -### -g -dwarf-version=3 %s 2>&1 | %FileCheck -check-prefix DWARF_VERSION_3 %s
+// DWARF_VERSION_3: -dwarf-version=3
+// RUN: not %swift_driver -dwarf-version=1 %s 2>&1 | %FileCheck -check-prefix INVALID_DWARF_VERSION %s
+// RUN: not %swift_driver -dwarf-version=6 %s 2>&1 | %FileCheck -check-prefix INVALID_DWARF_VERSION %s
+// RUN: not %swiftc_driver -dwarf-version=1 %s 2>&1 | %FileCheck -check-prefix INVALID_DWARF_VERSION %s
+// RUN: not %swiftc_driver -dwarf-version=6 %s 2>&1 | %FileCheck -check-prefix INVALID_DWARF_VERSION %s
+// INVALID_DWARF_VERSION: invalid value '{{1|6}}' in '-dwarf-version={{1|6}}'
+
 // RUN: not %swift_driver -gline-tables-only -debug-info-format=codeview %s 2>&1 | %FileCheck -check-prefix BAD_DEBUG_LEVEL_ERROR %s
 // RUN: not %swift_driver -gdwarf-types -debug-info-format=codeview %s 2>&1 | %FileCheck -check-prefix BAD_DEBUG_LEVEL_ERROR %s
 // RUN: not %swiftc_driver -gline-tables-only -debug-info-format=codeview %s 2>&1 | %FileCheck -check-prefix BAD_DEBUG_LEVEL_ERROR %s