[llvm] [PowerPC][AIX] Using milicode for memcmp instead of libcall (PR #147093)

[zhijian lin via llvm-commits]

diggerlin wrote:

> The compiler should not directly emit string calls. This needs an entry in RuntimeLibcalls.td to emit the call. 

The `memcmp` is in the RuntimeLibcalls.td, the ___memcmp has the same signature as memcmp. They  are  just have different function name, and memcmp is a lib call , but the   ___memcmp "millicode" routines, which are functions loaded at boot time into fixed addresses in kernel memory. when the AIX linker will replace the __memcmp  sybol with memory address of the  __memcmp 

> Further, this should not be based on a triple call in the DAG builder
sorry that I can not get the comment. can you explain in more detail ?

https://github.com/llvm/llvm-project/pull/147093