[Bug go/70787] New: No time and child info with -pg and gccgo

[vogt at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70787

            Bug ID: 70787
           Summary: No time and child info with -pg and gccgo
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: go
          Assignee: ian at airs dot com
          Reporter: vogt at linux dot vnet.ibm.com
                CC: cmang at google dot com, krebbel at gcc dot gnu.org
  Target Milestone: ---

It looks like the -pg option does something wrong for Go programs.  Example:

This program just wastes time in sub functions:
-- main.go --
package main
func foo () {
        var i int
        i = 0
        for (i < 1000) { i++ }
}
func bar () {
        var i int
        i = 0
        for (i < 1000) { i++ }
}
func main () {
        var i int
        i = 0
        for (i < 1000000) { foo(); foo(); bar(); i++ }
}
-- snip --

  $ gccgo -pg -O0 main.go
  $ ./a.out
  $ prof ./a.out gmoun.out 

=>

  index % time    self  children    called     name
                  0.00    0.00 3000000/3000000     main.main [8]
  [1]      0.0    0.00    0.00 3000000         frame_dummy [1]
           ^^^    ^^^^    ^^^^

(actual run time was about 5 seconds)

Even for this very simple program without Go library dependencies, no timing
information seems to be dumped into the gmon.out file.  Function calls have all
been counted in the "frame_dummy" bucket (double checked that functios have not
been inlied).

My vague first guess is that maybe the timing information is written to to some
place in memory but is read from a different place when generating gmon.out
because the profiling code is not aware of Gccgo's threading model(?).