Unwind-tables: move back to original logic outline for kind.

[t.p.northover]

Summary

There are lots of options interacting in complex ways here, and when moving to getDefaultUnwindTableLevel I had refactored this and changed behaviour in some cases (see tests added). So this reverts the basic structure of the logic back to the original (prior to 4388b56d52), while leaving the hook in the new style so targets remain simpler.

[abrachet]

Thanks! :)

[abrachet]

Ping :)

[t.p.northover]

Sorry about that, committed as e62b3a9375d8.

clang/lib/Driver/ToolChains/Clang.cpp

if (Freestanding)
     CmdArgs.push_back("-ffreestanding");
 
   Args.AddLastArg(CmdArgs, options::OPT_fno_knr_functions);
 
   // This is a coarse approximation of what llvm-gcc actually does, both
   // -fasynchronous-unwind-tables and -fnon-call-exceptions interact in more
   // complicated ways.
   auto SanitizeArgs = TC.getSanitizerArgs(Args);
-  auto UnwindTables = TC.getDefaultUnwindTableLevel(Args);
-
-  const bool HasSyncUnwindTables = Args.hasFlag(
-      options::OPT_funwind_tables, options::OPT_fno_unwind_tables, false);
-  if (Args.hasFlag(options::OPT_fasynchronous_unwind_tables,
-                   options::OPT_fno_asynchronous_unwind_tables,
-                   SanitizeArgs.needsUnwindTables()) &&
-      !Freestanding)
-    UnwindTables = ToolChain::UnwindTableLevel::Asynchronous;
-  else if (HasSyncUnwindTables)
-    UnwindTables = ToolChain::UnwindTableLevel::Synchronous;
-  else if (Args.hasFlag(options::OPT_fno_unwind_tables,
-                   options::OPT_fno_asynchronous_unwind_tables,
-                   options::OPT_funwind_tables, false) || Freestanding)
-    UnwindTables = ToolChain::UnwindTableLevel::None;
 
+  bool IsAsyncUnwindTablesDefault =
+      TC.getDefaultUnwindTableLevel(Args) == ToolChain::UnwindTableLevel::Asynchronous;
+  bool IsSyncUnwindTablesDefault =
+      TC.getDefaultUnwindTableLevel(Args) == ToolChain::UnwindTableLevel::Synchronous;
 
-  if (UnwindTables == ToolChain::UnwindTableLevel::Synchronous)
-    CmdArgs.push_back("-funwind-tables=1");
-  else if (UnwindTables == ToolChain::UnwindTableLevel::Asynchronous)
+  bool AsyncUnwindTables = Args.hasFlag(
+      options::OPT_fasynchronous_unwind_tables,
+      options::OPT_fno_asynchronous_unwind_tables,
+      (IsAsyncUnwindTablesDefault || SanitizeArgs.needsUnwindTables()) &&
+          !Freestanding);
+  bool UnwindTables =
+      Args.hasFlag(options::OPT_funwind_tables, options::OPT_fno_unwind_tables,
+                   IsSyncUnwindTablesDefault && !Freestanding);
+  if (AsyncUnwindTables)
     CmdArgs.push_back("-funwind-tables=2");
+  else if (UnwindTables)
+     CmdArgs.push_back("-funwind-tables=1");
 
   // Prepare `-aux-target-cpu` and `-aux-target-feature` unless
   // `--gpu-use-aux-triple-only` is specified.
   if (!Args.getLastArg(options::OPT_gpu_use_aux_triple_only) &&
       (IsCudaDevice || IsHIPDevice)) {
     const ArgList &HostArgs =
         C.getArgsForToolChain(nullptr, StringRef(), Action::OFK_None);
     std::string HostCPU =
if (Args.hasFlag(options::OPT_faddrsig, options::OPT_fno_addrsig,
                     TC.getTriple().isOSBinFormatCOFF()) &&
                        !TC.getTriple().isPS4() && !TC.getTriple().isVE() &&
                        !TC.getTriple().isOSNetBSD() &&
                        !Distro(D.getVFS(), TC.getTriple()).IsGentoo() &&
                        !TC.getTriple().isAndroid() && TC.useIntegratedAs()))
     CmdArgs.push_back("-faddrsig");
 
   if ((Triple.isOSBinFormatELF() || Triple.isOSBinFormatMachO()) &&
-      (EH || UnwindTables != ToolChain::UnwindTableLevel::None ||
+      (EH || UnwindTables || AsyncUnwindTables ||
        DebugInfoKind != codegenoptions::NoDebugInfo))
     CmdArgs.push_back("-D__GCC_HAVE_DWARF2_CFI_ASM=1");
 
   if (Arg *A = Args.getLastArg(options::OPT_fsymbol_partition_EQ)) {
     std::string Str = A->getAsString(Args);
     if (!TC.getTriple().isOSBinFormatELF())
       D.Diag(diag::err_drv_unsupported_opt_for_target)
           << Str << TC.getTripleString();

clang/test/Driver/clang-translation.c

 // RUN: %clang -target arm64-apple-ios10 -### -funwind-tables -S %s -arch arm64 2>&1 | \
 // RUN: FileCheck -check-prefix=ARM64-EXPLICIT-UWTABLE-APPLE %s
 //
 // RUN: %clang -target arm64-apple-ios10 -### -ffreestanding -funwind-tables -S %s -arch arm64 2>&1 | \
 // RUN: FileCheck -check-prefix=ARM64-EXPLICIT-UWTABLE-APPLE %s
 //
 // ARM64-EXPLICIT-UWTABLE-APPLE: -funwind-tables
 
+// RUN: %clang -target arm64-apple-macosx -### -ffreestanding -fasynchronous-unwind-tables %s 2>&1 | \
+// RUN: FileCheck --check-prefix=ASYNC-UNWIND-FREESTANDING %s
+//
+// ASYNC-UNWIND-FREESTANDING: -funwind-tables=2
+
+// Quite weird behaviour, but it's a long-standing default.
+// RUN: %clang -target x86_64-apple-macosx -### -fno-unwind-tables %s 2>&1 |\
+// RUN: FileCheck --check-prefix=NOUNWIND-IGNORED %s
+//
+// NOUNWIND-IGNORED: -funwind-tables=2
+
 // RUN: %clang -target arm64-apple-ios10 -fno-exceptions -### -S %s -arch arm64 2>&1 | \
 // RUN: FileCheck -check-prefix=ARM64-APPLE-EXCEP %s
 // ARM64-APPLE-EXCEP-NOT: -funwind-tables
 
 // RUN: %clang -target armv7k-apple-watchos4.0 -### -S %s -arch armv7k 2>&1 | \
 // RUN: FileCheck -check-prefix=ARMV7K-APPLE %s
 // ARMV7K-APPLE: -funwind-tables