Ensures that GDB prints stacktraces correctly for x64 builds when debugging t...

src/gdb-jit.h

Index: src/gdb-jit.h
===================================================================
--- src/gdb-jit.h	(revision 6445)
+++ src/gdb-jit.h	(working copy)
@@ -128,9 +128,107 @@
 
 #define GDBJIT(action) GDBJITInterface::action
 
+#ifdef V8_TARGET_ARCH_X64
+
+// This is currently only available (needed?) for AMD64.
+class UnwindInfoInterface {
+ public:
+
+  // An architecture dependent enum containing the various _states_ the program
+  // is in at various instructions. This information is used to generate the
+  // instructions for the CFI table. If UnwindInfoInterface is extended to other
+  // architectures, this will need to be selectively defined using #if ...
+  // #endif blocks.
+  enum UnwindInfoState {
+    UNWIND_STATE_AFTER_RBP_PUSH,
+    UNWIND_STATE_AFTER_RBP_SET,
+    UNWIND_STATE_AFTER_RBP_POP,
+    UNWIND_STATE_AFTER_RETURN,
+    UNWIND_STATE_MAX
+  };
+
+  struct UnwindInformation {
+    uintptr_t state_offsets_[UNWIND_STATE_MAX];
+    uintptr_t begin_;
+  };
+
+  UnwindInfoInterface();
+  ~UnwindInfoInterface();
+
+  static void SetStatePosition(uintptr_t pc, UnwindInfoState state);
+  static void SetStartAddress(uintptr_t pc);
+
+  // Unwind information emitted for the JS entry and exit stubs are accurate
+  // only at the call-sites. This is done since the more granular approach
+  // (which is used for regular compiled functions) will probably require
+  // considerable change to the internals. Since people are unlikely to step
+  // through the generated stubs, this is unlikely to be a problem.
+  // It is because of this reason, only the start and the end addresses for
+  // code stubs are required. This function does all the work - there is no
+  // need to create a dummy instance of this class for the mechanism to work
+  // correctly.
+  static void SetCodeStub(uintptr_t begin, uintptr_t length);
+
+ private:
+
+  struct UnwindInformationList {
+    UnwindInformation data_;
+    UnwindInformationList *next_;
+  };
+
+  static UnwindInformationList *info_;
+};
+
+
+#define SET_UNWIND_INFO(stage, pc) \
+  UnwindInfoInterface::SetStatePosition(pc, UnwindInfoInterface::stage)
+
+#define SET_UNWIND_INFO_START_ADDRESS(pc) \
+  UnwindInfoInterface::SetStartAddress(pc)
+
+#define SET_UNWIND_INFO_STUB(begin, len) \
+  UnwindInfoInterface::SetCodeStub(begin, len)
+
+
+inline void UnwindInfoInterface::SetStatePosition(
+    uintptr_t pc, UnwindInfoInterface::UnwindInfoState state) {
+  ASSERT(info_);
+  info_->data_.state_offsets_[state] = pc;
+  if (state)
+    ASSERT(info_->data_.state_offsets_[state-1] < pc);
+}
+
+
+inline void UnwindInfoInterface::SetStartAddress(uintptr_t pc) {
+  ASSERT(info_);
+  info_->data_.begin_ = pc;
+}
+
+
+inline UnwindInfoInterface::UnwindInfoInterface() {
+  UnwindInformationList *ulist = new UnwindInformationList();
+  ulist->next_ = info_;
+  info_ = ulist;
+}
+
+
+#else  // V8_TARGET_ARCH_X64
+
+
+#define SET_UNWIND_INFO(stage, pc) ((void) 0)
+#define SET_UNWIND_INFO_START_ADDRESS(pc) ((void) 0)
+#define SET_UNWIND_INFO_STUB(begin, len) ((void) 0)
+
+
+#endif  // V8_TARGET_ARCH_X64
+
+
 } }   // namespace v8::internal
 #else
 #define GDBJIT(action) ((void) 0)
+#define SET_UNWIND_INFO(stage, pc) ((void) 0)
+#define SET_UNWIND_INFO_START_ADDRESS(pc) ((void) 0)
+#define SET_UNWIND_INFO_STUB(begin, len)
 #endif
 
 #endif