test/codegen: add combined conversion and shift tests
This adds tests for type conversion and shifts, detailing various
poor bad code generation that currently exists for riscv64. This
will be addressed in future CLs.
Change-Id: Ie1d366dfe878832df691600f8500ef383da92848
Reviewed-on: https://go-review.googlesource.com/c/go/+/615678 Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com> Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Carlos Amedee <carlos@golang.org>