cmd/compile/internal/escape: escape values with >PtrSize alignment
After CL 381317 there exist values that may have an alignment greater
than the pointer size for that platform. Specifically, atomic.{Ui|I}nt64
may be aligned to 8 bytes on a 32-bit platform. If such a value, or
a container for the value, gets stack-allocated, it's possible that it
won't be aligned correctly, because the maximum alignment we enforce on
stacks is governed by the pointer size. Changing that would be a
significant undertaking, so just escape these values to the heap
instead, where we're sure they'll actually be aligned correctly.
Change is by rsc@, I'm just shepherding it through code review.
For #50860.
Change-Id: I51669561c0a13ecb84f821020e144c58cb528418
Reviewed-on: https://go-review.googlesource.com/c/go/+/410131
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>