[dev.link] cmd/link: clear lib.Textp2 after use

lib.Textp2 is used to assemble the global Textp2. It is not used
after that point. Free some memory.

Slightly reduces allocation: for linking cmd/compile,
Linksetup_GC     1.10MB ± 0%    0.84MB ± 0%  -23.43%  (p=0.008 n=5+5)

Change-Id: Iec4572e282655306d5ff3e490f8855d479e45acf
Reviewed-on: https://go-review.googlesource.com/c/go/+/228481
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index e996fc720d..59c022d5a9 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -2664,19 +2664,17 @@ func (l *Loader) AssignTextSymbolOrder(libs []*sym.Library, intlibs []bool, exts
 		}
 	}
 
-	// Now redo the assignment of text symbols to libs/units.
+	// Now assemble global textp, and assign text symbols to units.
 	for _, doInternal := range [2]bool{true, false} {
 		for idx, lib := range libs {
 			if intlibs[idx] != doInternal {
 				continue
 			}
-			libtextp2 := []sym.LoaderSym{}
 			lists := [2][]sym.LoaderSym{lib.Textp2, lib.DupTextSyms2}
 			for i, list := range lists {
 				for _, s := range list {
 					sym := Sym(s)
 					if l.attrReachable.Has(sym) && !assignedToUnit.Has(sym) {
-						libtextp2 = append(libtextp2, s)
 						textp2 = append(textp2, sym)
 						unit := l.SymUnit(sym)
 						if unit != nil {
@@ -2694,7 +2692,8 @@ func (l *Loader) AssignTextSymbolOrder(libs []*sym.Library, intlibs []bool, exts
 					}
 				}
 			}
-			lib.Textp2 = libtextp2
+			lib.Textp2 = nil
+			lib.DupTextSyms2 = nil
 		}
 	}