cmd/cgo: optimize cgoCheckPointer call

Currently cgoCheckPointer is only used with one optional argument.
Using a slice for the optional arguments is quite expensive, hence
replace it with a single interface{}. This results in ~30% improvement.

When checking struct fields, they quite often end up being without
pointers. Check this before calling cgoCheckPointer, which results in
additional ~20% improvement.

Inline some p == nil checks from cgoIsGoPointer which gives
additional ~15% improvement.

All of this translates to:

name                             old time/op  new time/op  delta
CgoCall/add-int-32               46.9ns ± 1%  46.6ns ± 1%   -0.75%  (p=0.000 n=18+20)
CgoCall/one-pointer-32            143ns ± 1%    87ns ± 1%  -38.96%  (p=0.000 n=20+20)
CgoCall/eight-pointers-32         767ns ± 0%   327ns ± 1%  -57.30%  (p=0.000 n=18+16)
CgoCall/eight-pointers-nil-32     110ns ± 1%    89ns ± 2%  -19.10%  (p=0.000 n=19+19)
CgoCall/eight-pointers-array-32  5.09µs ± 1%  3.56µs ± 2%  -30.09%  (p=0.000 n=19+19)
CgoCall/eight-pointers-slice-32  3.92µs ± 0%  2.57µs ± 2%  -34.48%  (p=0.000 n=20+20)

Change-Id: I2aa9f5ae8962a9a41a7fb1db0c300893109d0d75
Reviewed-on: https://go-review.googlesource.com/c/go/+/198081
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
4 files changed
tree: 840eca7df5abeaef6cfa9065f6c22c112facdf53
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. AUTHORS
  11. CONTRIBUTING.md
  12. CONTRIBUTORS
  13. favicon.ico
  14. LICENSE
  15. PATENTS
  16. README.md
  17. robots.txt
  18. SECURITY.md
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