Relying on the compiler to compensate for an unwieldy instruction set architecture is something that was tried explicitly with the Intel Itanium and failed hard.

\rant I feel that generally people often have a notion of the "compiler is unbeatable at optimizing", which is completely false: You can always start from compiler output when optimizing and you often have easy options that are inaccessible for the compiler because of language semantics/calling conventions etc. (=> but hand optimizing at instruction level is time consuming, time is expensive, and what the compiler does is basically free ;).

Compilers can absolutely not deal with the complexity of GPUs.