[Bug translator/20416] New: @entry(@perf("foo")) not translated correctly

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20416

            Bug ID: 20416
           Summary: @entry(@perf("foo")) not translated correctly
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
          Assignee: systemtap at sourceware dot org
          Reporter: fche at redhat dot com
  Target Milestone: ---

>From a uprobes .return call, @entry(@perf(...)) doesn't seem to propagate the
logic required to collect the @perf value in the .call synthetic probe:

% sudo stap -e '
global counts
probe perf.sw.cpu_clock.counter("foo") {}
probe process.function("main").return { counts <<< @perf("foo") -
@entry(@perf("foo")) }
' -c /bin/ls    
WARNING: never-assigned local variable '__perf_read_foo' (similar:
_entry_tvar_tid, counts): operator '@perf' at <input>:4:74
 source: probe process.function("main").return { counts <<< @perf("foo") -
@entry(@perf("foo")) }

The warning is appropriate: if one looks at the -p3 output, the __perf_read_foo
value is only collected in the .return probe, not in the synthetic .call.

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