> It just seems like Swift is probably already taking advantage of its optimizations.
The Go compiler performs nowhere near the level of optimization that LLVM does; LLVM is years and years ahead. However, LLVM is fundamentally a C compiler and so there can be impedance mismatch between Swift and LLVM. Hence SIL. This is what you're seeing, and once the gap is closed then Swift will reap the benefits of the hundreds of optimizations in LLVM.
The Go compiler performs nowhere near the level of optimization that LLVM does; LLVM is years and years ahead. However, LLVM is fundamentally a C compiler and so there can be impedance mismatch between Swift and LLVM. Hence SIL. This is what you're seeing, and once the gap is closed then Swift will reap the benefits of the hundreds of optimizations in LLVM.