Comment by drdrey

That's right, look at this thread for example:

https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20...

The Global Value Numbering pass in LLVM was iterating over `DenseMap<BasicBlock*, ...>`, so the iteration order was dependent on the value of BasicBlock pointers. This could lead to the same source files and compiler producing different binaries.