cmd/link: elide individual gcbits symbols

Same as we do for string symbols.

Fixes #11583.

Change-Id: Ia9264f6faf486697d987051b7f9851d37d8ad381
Reviewed-on: https://go-review.googlesource.com/12531
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

11 files changed, 19 insertions, 1 deletions

diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 24de6ef698..688c2785d1 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -337,6 +337,7 @@ const (
 	SSTRING
 	SGOSTRING
 	SGOFUNC
+	SGCBITS
 	SRODATA
 	SFUNCTAB
 	STYPELINK
diff --git a/src/cmd/link/internal/ld/dwarf.go b/src/cmd/link/internal/ld/dwarf.go
index b8fb2e6b55..41d820dc15 100644
--- a/src/cmd/link/internal/ld/dwarf.go
+++ b/src/cmd/link/internal/ld/dwarf.go
@@ -1419,6 +1419,9 @@ func defdwsymb(sym *LSym, s string, t int, v int64, size int64, ver int, gotype
 	if strings.HasPrefix(s, "go.string.") {
 		return
 	}
+	if strings.HasPrefix(s, "runtime.gcbits.") {
+		return
+	}
 
 	if strings.HasPrefix(s, "type.") && s != "type.*" && !strings.HasPrefix(s, "type..") {
 		defgotype(sym)
diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 1ce0348602..74e4445b86 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1793,6 +1793,7 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 			obj.SSTRING,
 			obj.SGOSTRING,
 			obj.SGOFUNC,
+			obj.SGCBITS,
 			obj.SWINDOWS:
 			if !s.Reachable {
 				continue
diff --git a/src/cmd/link/internal/ld/symtab.go b/src/cmd/link/internal/ld/symtab.go
index 7ceb64f941..5360ec15a1 100644
--- a/src/cmd/link/internal/ld/symtab.go
+++ b/src/cmd/link/internal/ld/symtab.go
@@ -373,6 +373,13 @@ func symtab() {
 	s.Reachable = true
 	symgofunc := s
 
+	s = Linklookup(Ctxt, "runtime.gcbits.*", 0)
+	s.Type = obj.SGCBITS
+	s.Local = true
+	s.Size = 0
+	s.Reachable = true
+	symgcbits := s
+
 	symtypelink := Linklookup(Ctxt, "runtime.typelink", 0)
 
 	symt = Linklookup(Ctxt, "runtime.symtab", 0)
@@ -411,6 +418,12 @@ func symtab() {
 			s.Outer = symgostring
 		}
 
+		if strings.HasPrefix(s.Name, "runtime.gcbits.") {
+			s.Type = obj.SGCBITS
+			s.Hide = 1
+			s.Outer = symgcbits
+		}
+
 		if strings.HasPrefix(s.Name, "go.func.") {
 			s.Type = obj.SGOFUNC
 			s.Hide = 1
diff --git a/src/cmd/newlink/testdata/Makefile b/src/cmd/newlink/testdata/Makefile
index 83e8a05195..d5df474248 100644
--- a/src/cmd/newlink/testdata/Makefile
+++ b/src/cmd/newlink/testdata/Makefile
@@ -9,7 +9,7 @@ ALL=\
 all: $(ALL)
 
 %.6: %.s
-	GOARCH=amd64 GOOS=darwin go tool asm -I $(shell go env GOROOT)/pkg/include -trimpath=$(shell pwd) $*.s
+	GOARCH=amd64 GOOS=darwin go tool asm -o $*.6 -I $(shell go env GOROOT)/pkg/include -trimpath=$(shell pwd) $*.s
 
 pclntab.s: genpcln.go
 	go run genpcln.go >pclntab.s
diff --git a/src/cmd/newlink/testdata/autosection.6 b/src/cmd/newlink/testdata/autosection.6
index 34aa5d3dbb..3681f70db8 100644
--- a/src/cmd/newlink/testdata/autosection.6
+++ b/src/cmd/newlink/testdata/autosection.6
diff --git a/src/cmd/newlink/testdata/autoweak.6 b/src/cmd/newlink/testdata/autoweak.6
index a86b841171..99cf465928 100644
--- a/src/cmd/newlink/testdata/autoweak.6
+++ b/src/cmd/newlink/testdata/autoweak.6
diff --git a/src/cmd/newlink/testdata/dead.6 b/src/cmd/newlink/testdata/dead.6
index 5e9b09c03e..5b17ef1adb 100644
--- a/src/cmd/newlink/testdata/dead.6
+++ b/src/cmd/newlink/testdata/dead.6
diff --git a/src/cmd/newlink/testdata/hello.6 b/src/cmd/newlink/testdata/hello.6
index 890cbbd016..1f08d2155e 100644
--- a/src/cmd/newlink/testdata/hello.6
+++ b/src/cmd/newlink/testdata/hello.6
diff --git a/src/cmd/newlink/testdata/layout.6 b/src/cmd/newlink/testdata/layout.6
index 748c836255..d1669866a4 100644
--- a/src/cmd/newlink/testdata/layout.6
+++ b/src/cmd/newlink/testdata/layout.6
diff --git a/src/cmd/newlink/testdata/pclntab.6 b/src/cmd/newlink/testdata/pclntab.6
index 8156698265..dfe53ddc38 100644
--- a/src/cmd/newlink/testdata/pclntab.6
+++ b/src/cmd/newlink/testdata/pclntab.6