ARMEB: Fix byte order of EH frame unwinding instructions

[cpirker]

Summary

Hi all,

This patch outputs the unwinding instructions in section "ARM.extab" in endian aware order.
Please review.

Thanks,
Christian

[jmolloy]

Hi Christian,

I have some style nitpicks, but I'm happy for you to commit once those are fixed.

Cheers,

James

lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

1216–1224

Style nitpicks: Spaces between operators and operands (x%4 -> x % 4, i+=4 -> i += 4), upper case I for loop induction variable.

[cpirker]

Hi James,

I updated the patch in respect to your comments.

Thanks,
Christian

[cpirker]

I committed this patch as rL208689.

lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

void ARMELFStreamer::emitFnEnd() {
   } else {
     // For the __aeabi_unwind_cpp_pr0, we have to emit the unwind opcodes in
     // the second word of exception index table entry.  The size of the unwind
     // opcodes should always be 4 bytes.
     assert(PersonalityIndex == ARM::EHABI::AEABI_UNWIND_CPP_PR0 &&
            "Compact model must use __aeabi_cpp_unwind_pr0 as personality");
     assert(Opcodes.size() == 4u &&
            "Unwind opcode size for __aeabi_cpp_unwind_pr0 must be equal to 4");
-    EmitBytes(StringRef(reinterpret_cast<const char*>(Opcodes.data()),
-                        Opcodes.size()));
+    uint64_t Intval = Opcodes[0] |
+                      Opcodes[1] << 8 |
+                      Opcodes[2] << 16 |
+                      Opcodes[3] << 24;
+    EmitIntValue(Intval, Opcodes.size());
   }
 
   // Switch to the section containing FnStart
   SwitchSection(&FnStart->getSection());
 
   // Clean exception handling frame information
   Reset();
 }
const MCSymbolRefExpr *PersonalityRef =
       MCSymbolRefExpr::Create(Personality,
                               MCSymbolRefExpr::VK_ARM_PREL31,
                               getContext());
 
     EmitValue(PersonalityRef, 4);
   }
 
   // Emit unwind opcodes
-  EmitBytes(StringRef(reinterpret_cast<const char *>(Opcodes.data()),
-                      Opcodes.size()));
+  assert((Opcodes.size() % 4) == 0 &&
+         "Unwind opcode size for __aeabi_cpp_unwind_pr0 must be multiple of 4");
+  for (unsigned I = 0; I != Opcodes.size(); I += 4) {
+    uint64_t Intval = Opcodes[I] |
+                      Opcodes[I + 1] << 8 |
+                      Opcodes[I + 2] << 16 |
+                      Opcodes[I + 3] << 24;
+    EmitIntValue(Intval, 4);
+  }
 
   // According to ARM EHABI section 9.2, if the __aeabi_unwind_cpp_pr1() or
   // __aeabi_unwind_cpp_pr2() is used, then the handler data must be emitted
   // after the unwind opcodes.  The handler data consists of several 32-bit
   // words, and should be terminated by zero.
   //
   // In case that the .handlerdata directive is not specified by the
   // programmer, we should emit zero to terminate the handler data.

test/CodeGen/ARM/big-endian-eh-unwind.ll

+; RUN: llc -march armeb -mattr v7 -filetype obj -o - %s | llvm-objdump -s - | FileCheck %s
+
+; ARM EHABI for big endian
+; This test case checks whether frame unwinding instructions are laid out in big endian format.
+; 
+; This is the LLVM assembly generated from following C++ code:
+;
+; extern void foo(int);
+; void test(int a, int b) {
+;   try {
+;   foo(a);
+; } catch (...) {
+;   foo(b);
+; }
+;}
+
+define void @_Z4testii(i32 %a, i32 %b) #0 {
+entry:
+  invoke void @_Z3fooi(i32 %a)
+          to label %try.cont unwind label %lpad
+
+lpad:                                             ; preds = %entry
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* null
+  %1 = extractvalue { i8*, i32 } %0, 0
+  %2 = tail call i8* @__cxa_begin_catch(i8* %1) #2
+  invoke void @_Z3fooi(i32 %b)
+          to label %invoke.cont2 unwind label %lpad1
+
+invoke.cont2:                                     ; preds = %lpad
+  tail call void @__cxa_end_catch()
+  br label %try.cont
+
+try.cont:                                         ; preds = %entry, %invoke.cont2
+  ret void
+
+lpad1:                                            ; preds = %lpad
+  %3 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  invoke void @__cxa_end_catch()
+          to label %eh.resume unwind label %terminate.lpad
+
+eh.resume:                                        ; preds = %lpad1
+  resume { i8*, i32 } %3
+
+terminate.lpad:                                   ; preds = %lpad1
+  %4 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* null
+  %5 = extractvalue { i8*, i32 } %4, 0
+  tail call void @__clang_call_terminate(i8* %5) #3
+  unreachable
+}
+
+declare void @_Z3fooi(i32) #0
+
+declare i32 @__gxx_personality_v0(...)
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @__cxa_end_catch()
+
+; Function Attrs: noinline noreturn nounwind
+define linkonce_odr hidden void @__clang_call_terminate(i8*) #1 {
+  %2 = tail call i8* @__cxa_begin_catch(i8* %0) #2
+  tail call void @_ZSt9terminatev() #3
+  unreachable
+}
+
+declare void @_ZSt9terminatev()
+
+; CHECK-LABEL: Contents of section .ARM.extab:
+; CHECK-NEXT: 0000 00000000 00b0b0b0
+