[libunwind] d6d0b65 - unwind: repair register restoration for OR1K

[Saleem Abdulrasool via cfe-commits]

Author: Saleem Abdulrasool
Date: 2021-08-02T16:36:37Z
New Revision: d6d0b6559e97a3d0b258814e870d3e19f3a7ffcc

URL: https://github.com/llvm/llvm-project/commit/d6d0b6559e97a3d0b258814e870d3e19f3a7ffcc
DIFF: https://github.com/llvm/llvm-project/commit/d6d0b6559e97a3d0b258814e870d3e19f3a7ffcc.diff

LOG: unwind: repair register restoration for OR1K

Currently, OR1K architecture put the program counter at offset 0x128 of
the current `or1k_thread_state_t`. However, the PC is restored after
updating the thread pointer in `r3`, which causes the PC to be fetched
incorrectly.

This patch swaps the order of restoration of `r9` and `r3`, such that
the PC is restored to `r9` using the current thread state.

Patch by Oi Chee Cheung!

Reviewed By: whitequark, compnerd

Differential Revision: https://reviews.llvm.org/D107042

Added: 
    

Modified: 
    libunwind/src/UnwindRegistersRestore.S

Removed: 
    


################################################################################
diff  --git a/libunwind/src/UnwindRegistersRestore.S b/libunwind/src/UnwindRegistersRestore.S
index d8bf1adee4168..c2106f32ee9f0 100644
--- a/libunwind/src/UnwindRegistersRestore.S
+++ b/libunwind/src/UnwindRegistersRestore.S
@@ -800,11 +800,12 @@ DEFINE_LIBUNWIND_FUNCTION(_ZN9libunwind14Registers_or1k6jumptoEv)
   l.lwz    r30,120(r3)
   l.lwz    r31,124(r3)
 
+  # load new pc into ra
+  l.lwz    r9, 128(r3)
+
   # at last, restore r3
   l.lwz    r3,  12(r3)
 
-  # load new pc into ra
-  l.lwz    r9, 128(r3)
   # jump to pc
   l.jr     r9
    l.nop