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Merge libcxxrt commit 5d8a15823a103bbc27f1bfdcf2b5aa008fab57dd

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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
This commit is contained in:
Mark Johnston 2022-08-08 12:30:56 -04:00
parent 2dd83b3f05
commit cbd1e83154
1 changed files with 3 additions and 1 deletions
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4
contrib/libcxxrt/exception.cc
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@ -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"