[dev.link] cmd/link: further reduce unnecessary field reading

Following CL 218479, there are more places where we don't need to
read all the fields.

Change-Id: I70889cd3f0514ef2c542317f3fe24f5ef99b41d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/220057
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

diff --git a/src/cmd/link/internal/ld/deadcode2.go b/src/cmd/link/internal/ld/deadcode2.go
index 06cc6d0daf2abb542f7b16d4268f225ba798a70b..4733f47446f69c3b65dd22c199aeee4755acc56a 100644 (file)
--- a/src/cmd/link/internal/ld/deadcode2.go
+++ b/src/cmd/link/internal/ld/deadcode2.go
@@ -86,7 +86,7 @@ func (d *deadcodePass2) init() {
                        // but we do keep the symbols it refers to.
                        exportsIdx := d.ldr.Lookup("go.plugin.exports", 0)
                        if exportsIdx != 0 {
-                               d.ReadRelocs(exportsIdx)
+                               d.ReadRelocSyms(exportsIdx)
                                for i := 0; i < len(d.rtmp); i++ {
                                        d.mark(d.rtmp[i].Sym, 0)
                                }
@@ -227,7 +227,7 @@ func (d *deadcodePass2) mark(symIdx, parent loader.Sym) {
 }
 
 func (d *deadcodePass2) markMethod(m methodref2) {
-       d.ReadRelocs(m.src)
+       d.ReadRelocSyms(m.src)
        d.mark(d.rtmp[m.r].Sym, m.src)
        d.mark(d.rtmp[m.r+1].Sym, m.src)
        d.mark(d.rtmp[m.r+2].Sym, m.src)
@@ -410,3 +410,9 @@ func (d *deadcodePass2) ReadRelocs(symIdx loader.Sym) {
        relocs := d.ldr.Relocs(symIdx)
        d.rtmp = relocs.ReadAll(d.rtmp)
 }
+
+// Like ReadRelocs, but only reads target symbols.
+func (d *deadcodePass2) ReadRelocSyms(symIdx loader.Sym) {
+       relocs := d.ldr.Relocs(symIdx)
+       d.rtmp = relocs.ReadSyms(d.rtmp)
+}