[dev.simd] cmd/compile: minor tweak for race detector
This makes the front-end a little bit less temp-happy
when instrumenting, which repairs the "is it a constant?"
test in the simd intrinsic conversion which is otherwise
broken by race detection.
Also, this will perhaps be better code.
Change-Id: I84b7a45b7bff62bb2c9f9662466b50858d288645
Reviewed-on: https://go-review.googlesource.com/c/go/+/685637
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Junyang Shao <shaojunyang@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com>