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[dev.link] cmd/link: add support to new deadcode for field tracking

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Fix up the new dead code pass to include support for populating the
ctxt "Reachparent" map, which is needed to support field tracking.
Since we don't have sym.Symbols created at the point where new dead
code runs, keep track of reachability using global symbol indices, and
then once loader.LoadFull is complete we can translate the index
mappings into symbol mappings.

The fieldtracking output is unfortunately different relative to
master, due to differences in the order in which symbols are
encountered in deadcode, but I have eyeballed the results to make sure
they look reasonable.

Change-Id: I48c7a4597f05c00f15af3bfd37fc15ab4d0017c2
Reviewed-on: https://go-review.googlesource.com/c/go/+/204342
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2019-10-30 12:31:55 -04:00
parent 63815923fc
commit 219922e95b
3 changed files with 39 additions and 15 deletions
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16
src/cmd/link/internal/ld/lib.go
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@ -2611,6 +2611,22 @@ func (ctxt *Link) loadlibfull() {
setupdynexp(ctxt)
// Populate ctxt.Reachparent if appropriate.
if ctxt.Reachparent != nil {
for i := 0; i < len(ctxt.loader.Reachparent); i++ {
p := ctxt.loader.Reachparent[i]
if p == 0 {
continue
}
if p == loader.Sym(i) {
panic("self-cycle in reachparent")
}
sym := ctxt.loader.Syms[i]
psym := ctxt.loader.Syms[p]
ctxt.Reachparent[sym] = psym
}
}
// Drop the reference.
ctxt.loader = nil
ctxt.cgodata = nil