[llvm] Initialize PreferredAlign in Function (PR #192156)

[Andrew Lenharth via llvm-commits]

darthscsi wrote:

This does appear to be a long standing issue with std::optional and valgrind.  I found numerous bugs, including some in gcc, about warnings.  They seem related to the std::optional being on the stack allowing some reorderings due to knowing the load won't trap.  Then you get a comparison which only depends on initialized bits, but whose input has uninitialized bits.

https://github.com/llvm/llvm-project/pull/192156