[llvm] [WIP][SPARC] Allow overaligned `alloca`s (PR #107223)

[Rainer Orth via llvm-commits]

rorth wrote:

> I admit I still find it hard to understand what is this testing, so may I ask for some explaination? I'm not very familiar with the constructs used there, and, particularly, the asan functions...

Neither am I.  I guess it's best to ask the author of the testcase, originally submitted in [Implement variable-sized alloca instrumentation (take 2).](https://reviews.llvm.org/D7098).  However, I cannot find a github account for him (m.ostapenko).  Maybe @yugr or @vitalybuka can shed some light?

FWIW, I've tried to build the testcase with gcc (which supports 32-bit ASan on SPARC just fine), but the test fails there, too.

https://github.com/llvm/llvm-project/pull/107223