[libunwind] [PAC][libunwind][AArch64] Keep LR signed when stored in context struct (PR #171717)

[Oliver Hunt via cfe-commits]

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@@ -683,42 +684,143 @@ DEFINE_LIBUNWIND_FUNCTION(__libunwind_Registers_arm64_jumpto)
   ldp    x28,x29, [x0, #0x0E0]
 
 #if defined(__ARM_FP) && __ARM_FP != 0
-  ldp    d0, d1,  [x0, #0x110]
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ojhunt wrote:

hmmm, I wonder if we can do something with this code so it's not as fragile w.r.t the state layout - this wouldn't be a change for this PR, more a "can we do something automatically" to just do this correctly (generator scripts or similar)

https://github.com/llvm/llvm-project/pull/171717