[AArch64][libunwind] Unwinding support for return address signing

- Follow up to revision r342895
- gcc would not build libunwind with the earlier patch as the autia1716
  instruction wasn't allowed to be assembled for pre armv8.3a targets
- The autia1716 instruction lives in the hint space encodings so is a valid
  instruction for all armv8a targets
- To work around this I have swapped out the autia1716 instruction for the hint
  instruction

Differential Revision: https://reviews.llvm.org/D55700

llvm-svn: 349140

1 files changed, 5 insertions, 0 deletions

diff --git a/libunwind/include/libunwind.h b/libunwind/include/libunwind.h
index 97d2b82290c..d824c131835 100644
--- a/libunwind/include/libunwind.h
+++ b/libunwind/include/libunwind.h
@@ -57,6 +57,9 @@ enum {
   UNW_EINVAL        = -6547, /* unsupported operation or bad value */
   UNW_EBADVERSION   = -6548, /* unwind info has unsupported version */
   UNW_ENOINFO       = -6549  /* no unwind info found */
+#if defined(_LIBUNWIND_TARGET_AARCH64) && !defined(_LIBUNWIND_IS_NATIVE_ONLY)
+  , UNW_ECROSSRASIGNING = -6550 /* cross unwind with return address signing */
+#endif
 };
 
 struct unw_context_t {
@@ -547,6 +550,8 @@ enum {
   UNW_ARM64_X31 = 31,
   UNW_ARM64_SP  = 31,
   // reserved block
+  UNW_ARM64_RA_SIGN_STATE = 34,
+  // reserved block
   UNW_ARM64_D0  = 64,
   UNW_ARM64_D1  = 65,
   UNW_ARM64_D2  = 66,