cmd/compile: bad position information for inlined functions

[mdempsky]

In the objdump output below, we see "q.go:3", which is nonsensical because this is the import statement's line number.

This happens because these instructions are getting their position information from the p.t struct literal's field initializers, but we're currently failing to serialize position information for OSTRUCTKEY. As a result, the nod(OSTRUCTKEY, ...) calls in bimport.go instead inherit the import statement's position information from lineno.

There are a handful of other nod calls (e.g., the OCONV nodes for importing OLITERALs, and the OIND and OADDR for importing OPTRLITs). These should all use explicit position information instead.

Related #19683.

/cc @hyangah @heschik @dr2chase

$ go tool compile p.go
$ go tool compile q.go
$ go tool link q.o
$ go tool objdump -s main.main a.out
TEXT main.main(SB) /tmp/q.go
  q.go:5            0x450970                64488b0c25f8ffffff      MOVQ FS:0xfffffff8, CX
  q.go:5            0x450979                488d842478ffffff        LEAQ 0xffffff78(SP), AX
  q.go:5            0x450981                483b4110                CMPQ 0x10(CX), AX
  q.go:5            0x450985                7641                    JBE 0x4509c8
  q.go:5            0x450987                4881ec08010000          SUBQ $0x108, SP
  q.go:5            0x45098e                4889ac2400010000        MOVQ BP, 0x100(SP)
  q.go:5            0x450996                488dac2400010000        LEAQ 0x100(SP), BP
  q.go:3            0x45099e                488d3c24                LEAQ 0(SP), DI
  q.go:3            0x4509a2                0f57c0                  XORPS X0, X0
  q.go:3            0x4509a5                48896c24f0              MOVQ BP, -0x10(SP)
  q.go:3            0x4509aa                488d6c24f0              LEAQ -0x10(SP), BP
  q.go:3            0x4509af                e8b0a3ffff              CALL 0x44ad64
  q.go:3            0x4509b4                488b6d00                MOVQ 0(BP), BP
  q.go:7            0x4509b8                488bac2400010000        MOVQ 0x100(SP), BP
  q.go:7            0x4509c0                4881c408010000          ADDQ $0x108, SP
  q.go:7            0x4509c7                c3                      RET
  q.go:5            0x4509c8                e8837dffff              CALL runtime.morestack_noctxt(SB)
  q.go:5            0x4509cd                eba1                    JMP main.main(SB)

$ cat p.go
package p

type t struct {
    b [256]byte
}

func F() interface{} {
    return &t{
            b: [256]byte{},
    }
}

$ cat q.go
package main

import "./p"

func main() {
    p.F()
}

[mdempsky]

@dr2chase fixed this with CL 80115.