[dev.link] cmd/link/internal/loader: reduce ABI alias postprocessing overhead
In loadObjFull when populating the sym.Reloc vector for live symbols,
avoid using the loader.SymType() method to determine if a relocation
targets an ABI alias; since invoking loader.SymType requires a
global-to-local index translation and a read from the object file.
Instead just look at the target symbol itself, which has already been
created at this point.
Hyperkube performance numbers for this change:
name old time/op new time/op delta
RelinkHyperkube 29.9s ± 2% 29.2s ± 3% -2.42% (p=0.000 n=20+20)
RelinkWithoutDebugHyperkube 22.0s ± 3% 21.4s ± 3% -2.58% (p=0.000 n=20+20)
Change-Id: Ib7696d8760dd0485240246d6d640668fbf451d71
Reviewed-on: https://go-review.googlesource.com/c/go/+/205257
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Jeremy Faller <jeremy@golang.org>