[PATCH] D15781: [compiler-rt] Add support for ARM EHABI to gcc_personality_v0.

[Timon Van Overveldt via llvm-commits]

timonvo marked 3 inline comments as done.

================
Comment at: lib/builtins/gcc_personality_v0.c:148
@@ +147,3 @@
+     * unwinding a single stack frame before returning (ARM EHABI Sec. 6.1).
+     */
+    if (__gnu_unwind_frame(exceptionObject, context) != _URC_OK)
----------------
I did run it through clang-format now (although I used an IndentWidth of 4 rather than the 2 LLVM style prescribes, because the rest of this file is already formatted that way).

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Comment at: lib/builtins/gcc_personality_v0.c:185
@@ +184,3 @@
+#if USING_ARM_EHABI
+    if ((state & _US_ACTION_MASK) == _US_VIRTUAL_UNWIND_FRAME)
+#else
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I believe what I have is correct. In short _US_VIRTUAL_UNWIND_FRAME is the equivalent of _UA_SEARCH_PHASE on other architectures. GCC's implementation has similar logic as well.

This is discussed in http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf, Sec 7.3. During Phase 1, the unwinder '... calls the PR, passing state
_US_VIRTUAL_UNWIND_FRAME, the UCB pointer, and an _Unwind_Context pointer for VRS access.' It's only during Phase 2 that the unwinder calls the PR with _US_UNWIND_FRAME_STARTING. During that phase we have to make sure that we call the landing pad if it exists, hence we can't bail early anymore here.


http://reviews.llvm.org/D15781