From e62b3a9375d8694efe5bf3d1409bec9be0d288e9 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Mon, 26 Sep 2022 13:26:36 +0100
Subject: [PATCH] Unwind-tables: move back to original logic outline for kind.

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. So this reverts the basic structure of the logic back to the
original, while leaving the hook in the new style.
---
 clang/lib/Driver/ToolChains/Clang.cpp | 39 ++++++++++++++++-------------------
 clang/test/Driver/clang-translation.c | 11 ++++++++++
 2 files changed, 29 insertions(+), 21 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index c93a727..5ea9e80 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5470,27 +5470,24 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // -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;
-
-
-  if (UnwindTables == ToolChain::UnwindTableLevel::Synchronous)
-    CmdArgs.push_back("-funwind-tables=1");
-  else if (UnwindTables == ToolChain::UnwindTableLevel::Asynchronous)
+
+  bool IsAsyncUnwindTablesDefault =
+      TC.getDefaultUnwindTableLevel(Args) == ToolChain::UnwindTableLevel::Asynchronous;
+  bool IsSyncUnwindTablesDefault =
+      TC.getDefaultUnwindTableLevel(Args) == ToolChain::UnwindTableLevel::Synchronous;
+
+  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.
@@ -7316,7 +7313,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     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");
 
diff --git a/clang/test/Driver/clang-translation.c b/clang/test/Driver/clang-translation.c
index 715b0b3..ca98ca5 100644
--- a/clang/test/Driver/clang-translation.c
+++ b/clang/test/Driver/clang-translation.c
@@ -99,6 +99,17 @@
 //
 // 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
-- 
2.7.4