cmd/compile: special-case MethodByName(string literal) to keep the DCE enabled.

Normally, a call to MethodByName() disables the DCE because the linker
assumes that any method can be accessed this way. This pessimises
the code generation for k8s.io/apimachinery which needs MethodByName()
to verify whether or not a struct implements DeepCopyInto(). It cannot
cast a struct to `interface { DeepCopyInto() Foo }` because the return
type may vary. Instead, it does the following:

  if m := reflect.ValueOf(obj).MethodByName("DeepCopyInto"); ... {

In this case there is no need to disable the DCE altogether. It
suffices to add a relocation to keep methods named DeepCopyInto().

Fixes #62257.

Change-Id: I583c2f04d8309a8807de75cd962c04151baeeb1b
Reviewed-on: https://go-review.googlesource.com/c/go/+/522436
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

0 files changed, 0 insertions, 0 deletions