[libunwind][ARM] Fix loading FP registers on big-endian targets

Summary:
The function Unwind-EHABI.cpp:_Unwind_VRS_Pop loads the saved values of
64-bit FP registers as two 32-bit words because they might not be
8-byte aligned. Combining these words into a 64-bit value has to be
done differently on big-endian platforms.

Reviewers: ostannard, john.brawn, dmgreen

Reviewed By: ostannard

Subscribers: kristof.beyls, christof, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D64996

llvm-svn: 366587

1 files changed, 7 insertions, 2 deletions

diff --git a/libunwind/src/Unwind-EHABI.cpp b/libunwind/src/Unwind-EHABI.cpp
index 4ff5e318b5f..8ee37d0fbe4 100644
--- a/libunwind/src/Unwind-EHABI.cpp
+++ b/libunwind/src/Unwind-EHABI.cpp
@@ -941,8 +941,13 @@ _Unwind_VRS_Pop(_Unwind_Context *context, _Unwind_VRS_RegClass regclass,
       // format 1", which is equivalent to FSTMD + a padding word.
       for (uint32_t i = first; i < end; ++i) {
         // SP is only 32-bit aligned so don't copy 64-bit at a time.
-        uint64_t value = *sp++;
-        value |= ((uint64_t)(*sp++)) << 32;
+        uint32_t w0 = *sp++;
+        uint32_t w1 = *sp++;
+#ifdef __LITTLE_ENDIAN__
+        uint64_t value = (w1 << 32) | w0;
+#else
+        uint64_t value = (w0 << 32) | w1;
+#endif
         if (_Unwind_VRS_Set(context, regclass, i, representation, &value) !=
             _UVRSR_OK)
           return _UVRSR_FAILED;