Compile time plan: in review as #384; --Ofast-compile not pursued
Compile time plan: CUDA measured (Tack's share halved; NVRTC's cache, CUBIN, Ofast-compile)
Compile time plan: what the disk cache leaves, and first calls with it warm
Compile time plan: MSL generation (0.86 to 0.54 s); status 10.1 s CPU, 9.2 s Metal
Compile time plan: Metal measured; status at 10.3 s (CPU), 9.5 s (Metal)
Compile time plan: step 4 (branches constants decide) done
Compile time plan: copy propagation and part of lowering done; LLVM's fixed cost measured
Compile time plan: step 3 (verify less) done
Compile time plan (#322): measurements over AhmedML's sweep and the steps