[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

2–4

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

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;
 }

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

test/CodeGen/AArch64/dwarf-cfi.ll

+; RUN: llc -mtriple aarch64-windows-gnu \
+; RUN:     -filetype=asm -o - %s \
+; RUN:   | FileCheck %s
+
+;-------------------------------------------------------------------------------
+; Test 1
+;-------------------------------------------------------------------------------
+; This is the LLVM assembly generated from following C++ code:
+;
+;   extern void print(int, int, int, int, int);
+;   extern void print(double, double, double, double, double);
+;
+;   void test(int a, int b, int c, int d, int e,
+;             double m, double n, double p, double q, double r) {
+;     try {
+;       print(a, b, c, d, e);
+;     } catch (...) {
+;       print(m, n, p, q, r);
+;     }
+;   }
+
+declare void @_Z5printiiiii(i32, i32, i32, i32, i32)
+
+declare void @_Z5printddddd(double, double, double, double, double)
+
+define void @_Z4testiiiiiddddd(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e,
+                               double %m, double %n, double %p,
+                               double %q, double %r) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+entry:
+  invoke void @_Z5printiiiii(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e)
+          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)
+  invoke void @_Z5printddddd(double %m, double %n, double %p,
+                             double %q, double %r)
+          to label %invoke.cont2 unwind label %lpad1
+
+invoke.cont2:
+  tail call void @__cxa_end_catch()
+  br label %try.cont
+
+try.cont:
+  ret void
+
+lpad1:
+  %3 = landingpad { i8*, i32 }
+          cleanup
+  invoke void @__cxa_end_catch()
+          to label %eh.resume unwind label %terminate.lpad
+
+eh.resume:
+  resume { i8*, i32 } %3
+
+terminate.lpad:
+  %4 = landingpad { i8*, i32 }
+          catch i8* null
+  %5 = extractvalue { i8*, i32 } %4, 0
+  tail call void @__clang_call_terminate(i8* %5)
+  unreachable
+}
+
+declare void @__clang_call_terminate(i8*)
+
+declare i32 @__gxx_personality_v0(...)
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @__cxa_end_catch()
+
+declare void @_ZSt9terminatev()
+
+; CHECK-LABEL: _Z4testiiiiiddddd:
+; CHECK:    .cfi_startproc
+; CHECK:    .cfi_personality 0, __gxx_personality_v0
+; CHECK:    .cfi_lsda 0, .Lexception0
+; CHECK:    str d12, [sp, #-64]!
+; CHECK:    stp d11, d10, [sp, #16]
+; CHECK:    stp d9, d8, [sp, #32]
+; CHECK:    stp x19, x30, [sp, #48]
+; CHECK:    .cfi_def_cfa_offset 64
+; CHECK:    .cfi_offset w30, -8
+; CHECK:    .cfi_offset w19, -16
+; CHECK:    .cfi_offset b8, -24
+; CHECK:    .cfi_offset b9, -32
+; CHECK:    .cfi_offset b10, -40
+; CHECK:    .cfi_offset b11, -48
+; CHECK:    .cfi_offset b12, -64
+; CHECK:    ldp x19, x30, [sp, #48]
+; CHECK:    ldp d9, d8, [sp, #32]
+; CHECK:    ldp d11, d10, [sp, #16]
+; CHECK:    ldr d12, [sp], #64
+; CHECK:    .cfi_endproc
+
+;-------------------------------------------------------------------------------
+; Test 2
+;-------------------------------------------------------------------------------
+
+declare void @throw_exception_2()
+
+define void @test2() {
+entry:
+  call void @throw_exception_2()
+  ret void
+}
+
+; CHECK-LABEL: test2:
+; CHECK:    .cfi_startproc
+; CHECK:    str x30, [sp, #-16]!
+; CHECK:    .cfi_def_cfa_offset 16
+; CHECK:    .cfi_offset w30, -16
+; CHECK:    ldr x30, [sp], #16
+; CHECK:    .cfi_endproc
+
+
+;-------------------------------------------------------------------------------
+; Test 3
+;-------------------------------------------------------------------------------
+
+declare void @throw_exception_3(i32)
+
+define i32 @test3(i32 %a, i32 %b, i32 %c, i32 %d,
+                  i32 %e, i32 %f, i32 %g, i32 %h) {
+entry:
+  %add = add nsw i32 %b, %a
+  %add1 = add nsw i32 %add, %c
+  %add2 = add nsw i32 %add1, %d
+  tail call void @throw_exception_3(i32 %add2)
+  %add3 = add nsw i32 %f, %e
+  %add4 = add nsw i32 %add3, %g
+  %add5 = add nsw i32 %add4, %h
+  tail call void @throw_exception_3(i32 %add5)
+  %add6 = add nsw i32 %add5, %add2
+  ret i32 %add6
+}
+
+; CHECK-LABEL: test3:
+; CHECK:    .cfi_startproc
+; CHECK:    stp x23, x22, [sp, #-48]!
+; CHECK:    stp x21, x20, [sp, #16]
+; CHECK:    stp x19, x30, [sp, #32]
+; CHECK:    .cfi_def_cfa_offset 48
+; CHECK:    .cfi_offset w30, -8
+; CHECK:    .cfi_offset w19, -16
+; CHECK:    .cfi_offset w20, -24
+; CHECK:    .cfi_offset w21, -32
+; CHECK:    .cfi_offset w22, -40
+; CHECK:    .cfi_offset w23, -48
+; CHECK:    .cfi_endproc
+
+
+;-------------------------------------------------------------------------------
+; Test 4
+;-------------------------------------------------------------------------------
+
+define void @test4() nounwind {
+entry:
+  ret void
+}
+
+; CHECK-LABEL: test4:
+; CHECK-NOT: .cfi_startproc
+; CHECK:     ret
+; CHECK-NOT: .cfi_endproc