This is why we will not have, and should not want, a "sufficiently smart compiler," but instead a "sufficiently predictable compiler." If the compiler is an enormously complex inference system, then tiny language-level changes can result in huge performance changes (see "space leaks" in Haskell, or "auto-vectorization" in basically anything). The solution isn't adding more knobs to the compiler; it's adding easier inter-language communication. Scripting languages like Matlab, Perl, Python, and R have been doing this right for decades: make a good effort at a specific domain (math, text, statistics), and make it easy to call into lower-level code for the key pieces.