[llvm] [hwasan] Optimize outlined memaccess for fixed shadow on Aarch64 (PR #88544)

[Thurston Dang via llvm-commits]

thurstond wrote:

Rebased on top of the memaccess intrinsics patch

The test case for this CL already exists in llvm-project/compiler-rt/test/hwasan/TestCases/Linux/fixed-shadow.c

https://github.com/llvm/llvm-project/pull/88544