From 62b0790a790c9c7adab0d5a8fa2ec659203c9252 Mon Sep 17 00:00:00 2001
From: Than McIntosh <thanm@google.com>
Date: Mon, 16 Mar 2020 15:24:48 -0400
Subject: [PATCH] [dev.link] cmd/compile: refactor aux handling in newobj sym
 traversal

Generalize symbol traversal code for aux symbols to allow for client
control over whether the walk incldues symbols referenced by
relocations on visited aux syms. This is not needed just yet but will
be required in order to support anonymous aux syms that have
relocations.

Change-Id: I898c1f398213c8d9d777dd3c40524a013b25e348
Reviewed-on: https://go-review.googlesource.com/c/go/+/223668
Reviewed-by: Cherry Zhang <cherryyz@google.com>
---
 src/cmd/internal/obj/objfile2.go |  2 +-
 src/cmd/internal/obj/sym.go      | 24 +++++++++++++++++++-----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/cmd/internal/obj/objfile2.go b/src/cmd/internal/obj/objfile2.go
index 359e82e138..d3e4bd4bea 100644
--- a/src/cmd/internal/obj/objfile2.go
+++ b/src/cmd/internal/obj/objfile2.go
@@ -454,7 +454,7 @@ func debugAsmEmit(ctxt *Link) {
 			fn := func(par *LSym, aux *LSym) {
 				writeAuxSymDebug(ctxt, par, aux)
 			}
-			ctxt.traverseAuxSyms(fn)
+			ctxt.traverseAuxSyms(traverseAux, fn)
 		}
 	}
 }
diff --git a/src/cmd/internal/obj/sym.go b/src/cmd/internal/obj/sym.go
index 9cd1786f67..ff5526ed45 100644
--- a/src/cmd/internal/obj/sym.go
+++ b/src/cmd/internal/obj/sym.go
@@ -297,15 +297,20 @@ func (ctxt *Link) traverseSyms(flag traverseFlag, fn func(*LSym)) {
 					f := func(parent *LSym, aux *LSym) {
 						fn(aux)
 					}
-					ctxt.traverseFuncAux(s, f)
+					ctxt.traverseFuncAux(flag, s, f)
 				}
 			}
 		}
 	}
 }
 
-func (ctxt *Link) traverseFuncAux(fsym *LSym, fn func(parent *LSym, aux *LSym)) {
+func (ctxt *Link) traverseFuncAux(flag traverseFlag, fsym *LSym, fn func(parent *LSym, aux *LSym)) {
 	pc := &fsym.Func.Pcln
+	if flag&traverseAux == 0 {
+		// NB: should it become necessary to walk aux sym reloc references
+		// without walking the aux syms themselves, this can be changed.
+		panic("should not be here")
+	}
 	for _, d := range pc.Funcdata {
 		if d != nil {
 			fn(fsym, d)
@@ -331,21 +336,30 @@ func (ctxt *Link) traverseFuncAux(fsym *LSym, fn func(parent *LSym, aux *LSym))
 			continue
 		}
 		fn(fsym, dws)
+		if flag&traverseRefs != 0 {
+			for _, r := range dws.R {
+				if r.Sym != nil {
+					fn(dws, r.Sym)
+				}
+			}
+		}
 	}
 }
 
 // Traverse aux symbols, calling fn for each sym/aux pair.
-func (ctxt *Link) traverseAuxSyms(fn func(parent *LSym, aux *LSym)) {
+func (ctxt *Link) traverseAuxSyms(flag traverseFlag, fn func(parent *LSym, aux *LSym)) {
 	lists := [][]*LSym{ctxt.Text, ctxt.Data, ctxt.ABIAliases}
 	for _, list := range lists {
 		for _, s := range list {
 			if s.Gotype != nil {
-				fn(s, s.Gotype)
+				if flag&traverseDefs != 0 {
+					fn(s, s.Gotype)
+				}
 			}
 			if s.Type != objabi.STEXT {
 				continue
 			}
-			ctxt.traverseFuncAux(s, fn)
+			ctxt.traverseFuncAux(flag, s, fn)
 		}
 	}
 }
-- 
2.50.0