From 49f4b5a4f5257e17cc62ad5d7862fdb4a5cfa7a0 Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Wed, 12 Apr 2017 06:11:08 -0700
Subject: [PATCH] cmd/internal/obj: remove Link.Plan9privates

Move it to the x86 package, matching our handling
of deferreturn in x86 and arm.
While we're here, improve the concurrency safety
of both Plan9privates and deferreturn
by eagerly initializing them in instinit.

Updates #15756

Change-Id: If3b1995c1e4ec816a5443a18f8d715631967a8b1
Reviewed-on: https://go-review.googlesource.com/40408
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
---
 src/cmd/internal/obj/link.go     |  1 -
 src/cmd/internal/obj/x86/asm6.go | 26 ++++++++++++++------------
 src/cmd/internal/obj/x86/obj6.go |  4 ----
 3 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 82b12105da..d5d96f792e 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -725,7 +725,6 @@ type Link struct {
 	PosTable      src.PosTable
 	InlTree       InlTree // global inlining tree used by gc/inl.go
 	Imports       []string
-	Plan9privates *LSym
 	DiagFunc      func(string, ...interface{})
 	DebugInfo     func(fn *LSym, curfn interface{}) []*dwarf.Var // if non-nil, curfn is a *gc.Node
 	Errors        int
diff --git a/src/cmd/internal/obj/x86/asm6.go b/src/cmd/internal/obj/x86/asm6.go
index 3fd5052e65..8d55f9cfe0 100644
--- a/src/cmd/internal/obj/x86/asm6.go
+++ b/src/cmd/internal/obj/x86/asm6.go
@@ -39,6 +39,11 @@ import (
 	"strings"
 )
 
+var (
+	plan9privates *obj.LSym
+	deferreturn   *obj.LSym
+)
+
 // Instruction layout.
 
 const (
@@ -1830,10 +1835,6 @@ func span6(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
 	n := 0
 	var c int32
 	errors := ctxt.Errors
-	var deferreturn *obj.LSym
-	if ctxt.Headtype == obj.Hnacl {
-		deferreturn = ctxt.Lookup("runtime.deferreturn", 0)
-	}
 	for {
 		loop := int32(0)
 		for i := range s.R {
@@ -1973,6 +1974,13 @@ func instinit(ctxt *obj.Link) {
 		return
 	}
 
+	switch ctxt.Headtype {
+	case obj.Hplan9:
+		plan9privates = ctxt.Lookup("_privates", 0)
+	case obj.Hnacl:
+		deferreturn = ctxt.Lookup("runtime.deferreturn", 0)
+	}
+
 	for i := 1; optab[i].as != 0; i++ {
 		c := optab[i].as
 		if opindex[c&obj.AMask] != nil {
@@ -4108,13 +4116,10 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 								asmbuf.asmand(ctxt, cursym, p, &pp.From, &p.To)
 							}
 						case obj.Hplan9:
-							if ctxt.Plan9privates == nil {
-								ctxt.Plan9privates = ctxt.Lookup("_privates", 0)
-							}
 							pp.From = obj.Addr{}
 							pp.From.Type = obj.TYPE_MEM
 							pp.From.Name = obj.NAME_EXTERN
-							pp.From.Sym = ctxt.Plan9privates
+							pp.From.Sym = plan9privates
 							pp.From.Offset = 0
 							pp.From.Index = REG_NONE
 							asmbuf.Put1(0x8B)
@@ -4164,13 +4169,10 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 						asmbuf.PutInt32(0)
 
 					case obj.Hplan9:
-						if ctxt.Plan9privates == nil {
-							ctxt.Plan9privates = ctxt.Lookup("_privates", 0)
-						}
 						pp.From = obj.Addr{}
 						pp.From.Type = obj.TYPE_MEM
 						pp.From.Name = obj.NAME_EXTERN
-						pp.From.Sym = ctxt.Plan9privates
+						pp.From.Sym = plan9privates
 						pp.From.Offset = 0
 						pp.From.Index = REG_NONE
 						asmbuf.rexflag |= Pw
diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go
index b931871cee..fc39efeaa8 100644
--- a/src/cmd/internal/obj/x86/obj6.go
+++ b/src/cmd/internal/obj/x86/obj6.go
@@ -589,10 +589,6 @@ func nacladdr(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) {
 }
 
 func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
-	if ctxt.Headtype == obj.Hplan9 && ctxt.Plan9privates == nil {
-		ctxt.Plan9privates = ctxt.Lookup("_privates", 0)
-	}
-
 	if cursym.Text == nil || cursym.Text.Link == nil {
 		return
 	}