Not only that, but "[target data layout] is used by the mid-level optimizers to improve code, and this only works if it matches what the ultimate code generator

Not only that, but "[target data layout] is used by the mid-level optimizers to improve code, and this only works if it matches what the ultimate code generator uses. There is no way to generate IR that does not embed this target-specific detail into the IR. If you don’t specify the string, the default specifications will be used to generate a Data Layout and the optimization phases will operate accordingly and introduce target specificity into the IR with respect to these default specifications." Much of this article is simply inaccurate speculation. [1] http://llvm.org/docs/LangRef.html#data-layout http://llvm.org/docs/LangRef.html#data-layout