[release-branch.go1.17] cmd/compile: fold handling OCONV logic to separate function
So next CL can re-use the logic to perform checkptr instrumentation.
For #48561
Change-Id: I3241e9c3c84da04db71fd1d4fd83cb76b2e18521
Reviewed-on: https://go-review.googlesource.com/c/go/+/345435
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
(cherry picked from commit
8fad81cd6294776c63a3e9a5820f196949974861)
Reviewed-on: https://go-review.googlesource.com/c/go/+/354352
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>