[llvm] [BOLT][AArch64] Fixed indirect call instrumentation snippet (PR #141918)

[Alexey Moksyakov via llvm-commits]

yavtuk wrote:

"
The new flow is:

callsite code calls the entry handler
entry handler
if the hook is set up: it runs, preserving LR
then it calls the exit handler, which:
restores condition flags and x0/x1
returns to the original callsite to do the (preserved) call
"

yes, you are right here, the main difference that  before we called indirect target inside instrumented library and used x16 to return back. in the patch indirect call leave as-is, inside instrumentation library only counters for target function is increased with store/load all touch registers values  

https://github.com/llvm/llvm-project/pull/141918