cmd/internal/obj: frame pointer missing for small functions

[randall77]

func f() {
    g()
}

Generates

000000000044cc60 <main.f>:
  44cc60:       64 48 8b 0c 25 f8 ff    mov    %fs:0xfffffffffffffff8,%rcx
  44cc67:       ff ff 
  44cc69:       48 3b 61 10             cmp    0x10(%rcx),%rsp
  44cc6d:       76 06                   jbe    44cc75 <main.f+0x15>
  44cc6f:       e8 0c 00 00 00          callq  44cc80 <main.g>
  44cc74:       c3                      retq   
  44cc75:       e8 f6 85 ff ff          callq  445270 <runtime.morestack_noctxt>
  44cc7a:       eb e4                   jmp    44cc60 <main.f>

There's no frame pointer manipulation here. There probably should be, backtraces done by the kernel profiler will miss (or even be messed up?) by this omission.

Hit this issue while working on #16638. We require frame pointers on every frame to make callers work using frame pointers.
@dvyukov
@rsc
@aclements

[gopherbot]

CL https://golang.org/cl/33754 mentions this issue.