[gsg]

This is nonsense. Modern compilers don't work by generating the results you see with -O0 and then optimising; the poor quality of -O0 code is the result of skipping register allocation.

> Dataflow-directed, "work backwards" techniques might be the solution

Destination driven code generation is a known technique. It doesn't generate good enough results to have gotten much attention (better than what you get from -O0, though).