git: cbd1e83154af - main - Merge libcxxrt commit 5d8a15823a103bbc27f1bfdcf2b5aa008fab57dd

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=cbd1e83154af8bae3daa3919bb2746d587436515

commit cbd1e83154af8bae3daa3919bb2746d587436515
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-08-08 16:30:56 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-08-08 16:50:48 +0000

    Merge libcxxrt commit 5d8a15823a103bbc27f1bfdcf2b5aa008fab57dd
    
      Fix two bugs in __cxa_end_cleanup()
    
      Per the EHABI32 specification, __cxa_end_cleanup must take care to
      preserve registers before calling _Unwind_Resume().  So, libcxxrt uses
      an assembly stub which preserves caller-saved registers around the call
      to __cxa_get_cleanup().  But:
      - it failed to restore them properly,
      - it did not preserve the link register.
    
      Fix both of these problems.  This is needed to fix exception unwinding
      on FreeBSD with LLVM 14.  Note that r4 is callee-saved but is pushed
      onto the stack to preserve stack pointer alignment.
    
      Sponsored-by: The FreeBSD Foundation
    
    MFC after:      1 week
---
 contrib/libcxxrt/exception.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/contrib/libcxxrt/exception.cc b/contrib/libcxxrt/exception.cc
index f28082ab7e80..6c5196876b10 100644
--- a/contrib/libcxxrt/exception.cc
+++ b/contrib/libcxxrt/exception.cc
@@ -1577,8 +1577,10 @@ asm (
 ".type __cxa_end_cleanup, \"function\"   \n"
 "__cxa_end_cleanup:                      \n"
 "	push {r1, r2, r3, r4}                \n"
+"	mov r4, lr                           \n"
 "	bl __cxa_get_cleanup                 \n"
-"	push {r1, r2, r3, r4}                \n"
+"	mov lr, r4                           \n"
+"	pop {r1, r2, r3, r4}                 \n"
 "	b _Unwind_Resume                     \n"
 "	bl abort                             \n"
 ".popsection                             \n"