method_fastcall4.patch benchmark results. It's not the first time that I notice that fannkuch and nbody benchmarks become slower. I guess that it's effect of changing code placement because of unrelated change in the C code.

Results don't seem significant on such macro benchmarks (may be random performance changes due to code placement). IMHO the change is worth it! "1.46x faster (-31%)" on a microbenchmark is significant and the change is small.

$ python3 -m perf compare_to /home/haypo/benchmarks/2017-02-08_15-49-default-f507545ad22a.json method_fastcall4_ref_f507545ad22a.json -G --min-speed=5
Slower (2):
- fannkuch: 900 ms +- 20 ms -> 994 ms +- 10 ms: 1.10x slower (+10%)
- nbody: 215 ms +- 3 ms -> 228 ms +- 4 ms: 1.06x slower (+6%)

Faster (3):
- scimark_lu: 357 ms +- 23 ms -> 298 ms +- 8 ms: 1.19x faster (-16%)
- scimark_sor: 400 ms +- 11 ms -> 355 ms +- 12 ms: 1.12x faster (-11%)
- raytrace: 1.05 sec +- 0.01 sec -> 984 ms +- 15 ms: 1.07x faster (-6%)

Benchmark hidden because not significant (59): (...)