cmd/compile: fix SIMD type parameter instantiation
When a SIMD type is used to instantiate a type parameter, the SIMD's
underlying type is its shape. This shape type must be marked as a SIMD
type, otherwise, the backend will confuse and does not know how to put
this SIMD type to proper registers.
Fixing this by marking a type as SIMD type if its underlying is already
a SIMD one.
Fixes #77444
Change-Id: I745c474469889c94bc68435472ba4820e9f752a1
Reviewed-on: https://go-review.googlesource.com/c/go/+/742320
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>