[llvm-dev] Non-determinism in LLVM codegen

[regehr via llvm-dev]

> Given a flag (-mllvm -reverse-iterate) this patch will enable iteration
> of SmallPtrSet in reverse order. The idea is to compile the same source
> with and without this flag and expect the code to not change.

This is really cool!

Another potential source for non-determinism is undefined behavior.  In 
a Debug LLVM from last night I got 22 unexpected failures when testing 
under Valgrind.

John