[ExecutionEngine] Use libunwind logic if __APPLE__

[hvdijk]

Summary

One of the bots has a test failure that appears to suggest that Apple may have libunwind's register_frame without unw_add_dynamic_fde, so the check I did in D106129 fails. Until this can be looked into deeper, restore the previous behaviour if APPLE is defined, but keep the new behaviour otherwise.

[lhames]

LGTM, but Azhar just committed the same fix in d898693f72fc so there's nothing to do here. :)

llvm/lib/ExecutionEngine/Orc/TargetProcess/RegisterEHFrames.cpp

static Error deregisterFrameWrapper(const void *P) {
   }
 
   return make_error<StringError>("could not deregister eh-frame: "
                                  "__deregister_frame function not found",
                                  inconvertibleErrorCode());
 }
 #endif
 
-#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
+#if defined(HAVE_UNW_ADD_DYNAMIC_FDE) || defined(__APPLE__)
 
 template <typename HandleFDEFn>
 Error walkLibunwindEHFrameSection(const char *const SectionStart,
                                   size_t SectionSize, HandleFDEFn HandleFDE) {
   const char *CurCFIRecord = SectionStart;
   const char *End = SectionStart + SectionSize;
   uint64_t Size = *reinterpret_cast<const uint32_t *>(CurCFIRecord);
 
while (CurCFIRecord != End && Size != 0) {
     CurCFIRecord += Size;
 
     Size = *reinterpret_cast<const uint32_t *>(CurCFIRecord);
   }
 
   return Error::success();
 }
 
-#endif // HAVE_UNW_ADD_DYNAMIC_FDE
+#endif // defined(HAVE_UNW_ADD_DYNAMIC_FDE) || defined(__APPLE__)
 
 Error registerEHFrameSection(const void *EHFrameSectionAddr,
                              size_t EHFrameSectionSize) {
   /* libgcc and libunwind __register_frame behave differently. We use the
    * presence of __unw_add_dynamic_fde to detect libunwind. */
-#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
+#if defined(HAVE_UNW_ADD_DYNAMIC_FDE) || defined(__APPLE__)
   // With libunwind, __register_frame has to be called for each FDE entry.
   return walkLibunwindEHFrameSection(
       static_cast<const char *>(EHFrameSectionAddr), EHFrameSectionSize,
       registerFrameWrapper);
 #else
   // With libgcc, __register_frame takes a single argument:
   // a pointer to the start of the .eh_frame section.
 
   // How can it find the end? Because crtendS.o is linked
   // in and it has an .eh_frame section with four zero chars.
   return registerFrameWrapper(EHFrameSectionAddr);
 #endif
 }
 
 Error deregisterEHFrameSection(const void *EHFrameSectionAddr,
                                size_t EHFrameSectionSize) {
-#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
+#if defined(HAVE_UNW_ADD_DYNAMIC_FDE) || defined(__APPLE__)
   return walkLibunwindEHFrameSection(
       static_cast<const char *>(EHFrameSectionAddr), EHFrameSectionSize,
       deregisterFrameWrapper);
 #else
   return deregisterFrameWrapper(EHFrameSectionAddr);
 #endif
 }
 

llvm/lib/ExecutionEngine/RuntimeDyld/RTDyldMemoryManager.cpp

static void __deregister_frame(void *p) {
   }
   if (df)
     df(p);
 }
 #endif
 
 /* libgcc and libunwind __register_frame behave differently. We use the presence
  * of __unw_add_dynamic_fde to detect libunwind. */
-#ifdef HAVE_UNW_ADD_DYNAMIC_FDE
+#if defined(HAVE_UNW_ADD_DYNAMIC_FDE) || defined(__APPLE__)
 
 static const char *processFDE(const char *Entry, bool isDeregister) {
   const char *P = Entry;
   uint32_t Length = *((const uint32_t *)P);
   P += 4;
   uint32_t Offset = *((const uint32_t *)P);
   if (Offset != 0) {
     if (isDeregister)