cmd/compile/internal/gc: minor code reorg (cleanup)
cmd/compile/internal/gc: minor code reorg (cleanup)

Found while tracking down #26855.

Change-Id: Ice137fe390820ba351e1c7439b6a9a1b3bdc966b
Reviewed-on: https://go-review.googlesource.com/136396
Run-TryBot: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>

josharian/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,cloudflare/go,josharian/go,cloudflare/go,golang/go,CAFxX/go,nawawi/go,josharian/go,cloudflare/go,CAFxX/go,golang/go,nawawi/go,golang/go,golang/go,akutz/go,nawawi/go,akutz/go,CAFxX/go,josharian/go,akutz/go,CAFxX/go,golang/go,cloudflare/go,akutz/go,josharian/go,josharian/go,cloudflare/go,CAFxX/go,cloudflare/go,nawawi/go,CAFxX/go,akutz/go,cloudflare/go,josharian/go,nawawi/go,josharian/go,nawawi/go,golang/go,CAFxX/go,akutz/go,nawawi/go,akutz/go,akutz/go,golang/go