[PATCH] D45321: [atomics] Fix runtime calls for misaligned atomics

[Tim Northover via Phabricator via llvm-commits]

t.p.northover added a comment.

Atomics accessed via C11 _Atomic and C++11 std::atomic will be suitably aligned, but there's a reasonable amount of legacy code that uses the GCC builtins on non-atomic types (of unknown alignment) and this is what Clang uses to implement those accesses when they come up. Also, on the LLVM side there are even fewer restrictions and `load atomic i32, i32* %ptr monotonic, align 1` is perfectly valid IR that gets lowered to these calls.

In parallel I'm trying to add a performance warning for when Clang hits this issue and is forced to generate libcalls.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D45321