[AArch64] Use dwarf exception handling on MinGW

[mstorsjo]

Summary

This is the only change needed for enabling dwarf exceptions on MinGW, no further changes are needed in clang or in libunwind.

[compnerd]

What exactly is the test intending to test? If its that the CFI is generated, I think that the input is too complex. Something simpler like:

void f();
void g() { try { f(); } catch (...) { } }

should be sufficient.

[mstorsjo]

Simplified the test as suggested.

[mstorsjo]

The same goes here as for ARM as well - ideally we should probably use windows exception tables here as well, but on aarch64, there's even more things to do to get that working - while the dwarf version seems to work fine (at least when tested in wine) so far.

[compnerd]

test/CodeGen/AArch64/dwarf-cfi.ll

1–3 ↗

(On Diff #121368)

The split over multiple lines is not really helpful (especially when copy/pasting to debug).

llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp

AArch64MCAsmInfoELF::AArch64MCAsmInfoELF(const Triple &T) {
   HasIdentDirective = true;
 }
 
 AArch64MCAsmInfoCOFF::AArch64MCAsmInfoCOFF() {
   PrivateGlobalPrefix = ".L";
   PrivateLabelPrefix = ".L";
   AlignmentIsInBytes = false;
   SupportsDebugInformation = true;
-  ExceptionsType = ExceptionHandling::WinEH;
+  CodePointerSize = 8;
 }
 
 AArch64MCAsmInfoMicrosoftCOFF::AArch64MCAsmInfoMicrosoftCOFF() {
   CommentString = ";";
+  ExceptionsType = ExceptionHandling::WinEH;
 }
 
 AArch64MCAsmInfoGNUCOFF::AArch64MCAsmInfoGNUCOFF() {
   CommentString = "//";
+  ExceptionsType = ExceptionHandling::DwarfCFI;
 }

llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64WinCOFFStreamer.cpp

 class AArch64WinCOFFStreamer : public MCWinCOFFStreamer {
 public:
   friend class AArch64TargetWinCOFFStreamer;
 
   AArch64WinCOFFStreamer(MCContext &C, std::unique_ptr<MCAsmBackend> AB,
                          std::unique_ptr<MCCodeEmitter> CE,
                          raw_pwrite_stream &OS)
       : MCWinCOFFStreamer(C, std::move(AB), std::move(CE), OS) {}
+
+  void FinishImpl() override;
 };
+
+void AArch64WinCOFFStreamer::FinishImpl() {
+  EmitFrames(nullptr);
+
+  MCWinCOFFStreamer::FinishImpl();
+}
 } // end anonymous namespace
 
 namespace llvm {
 MCWinCOFFStreamer *createAArch64WinCOFFStreamer(
     MCContext &Context, std::unique_ptr<MCAsmBackend> MAB,
     raw_pwrite_stream &OS, std::unique_ptr<MCCodeEmitter> Emitter,
     bool RelaxAll, bool IncrementalLinkerCompatible) {
   auto *S = new AArch64WinCOFFStreamer(Context, std::move(MAB),
                                        std::move(Emitter), OS);
   S->getAssembler().setIncrementalLinkerCompatible(IncrementalLinkerCompatible);
   return S;
 }
 
 } // end llvm namespace

llvm/trunk/test/CodeGen/AArch64/dwarf-cfi.ll

+; RUN: llc -mtriple aarch64-windows-gnu -filetype=asm -o - %s | FileCheck %s
+
+define void @_Z1gv() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+entry:
+  invoke void @_Z1fv()
+          to label %try.cont unwind label %lpad
+
+lpad:
+  %0 = landingpad { i8*, i32 }
+          catch i8* null
+  %1 = extractvalue { i8*, i32 } %0, 0
+  %2 = tail call i8* @__cxa_begin_catch(i8* %1) #2
+  tail call void @__cxa_end_catch()
+  br label %try.cont
+
+try.cont:
+  ret void
+}
+
+declare void @_Z1fv()
+
+declare i32 @__gxx_personality_v0(...)
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @__cxa_end_catch()
+
+; CHECK-LABEL: _Z1gv:
+; CHECK:    .cfi_startproc
+; CHECK:    .cfi_personality 0, __gxx_personality_v0
+; CHECK:    .cfi_lsda 0, .Lexception0
+; CHECK:    str x30, [sp, #-16]!
+; CHECK:    .cfi_def_cfa_offset 16
+; CHECK:    .cfi_offset w30, -16
+; CHECK:    ldr x30, [sp], #16
+; CHECK:    .cfi_endproc