Because fp is not aligned 16 byte, when simpleperf use "--call-graph fp" mode, Before Andoroid 12 system, the backtrace stack will broken.

Becasue Before the Android 12 , the Libunwind require the stack 16 byte align.

So, How We modify the compiler to generate the stack 16 byte align?

PS: before this patch(https://github.com/llvm/llvm-project/commit/643adb55769ecb12e0377dab60de50def15d2cea) ,the clang generate stack is 16 byte align.

Start by reviewing the referenced LLVM patch and the reported simpleperf --call-graph fp behavior on pre-Android 12 systems. Compare the compiler-generated stack alignment with libunwind's requirements and determine the affected compiler entry point; done means a justified change and a regression test demonstrating a valid backtrace.

Written by the indexing model from the issue text.