cmd/internal/obj, cmd/link, runtime: lots of TLS cleanup

It's particularly nice to get rid of the android special cases in the linker.

Change-Id: I516363af7ce8a6b2f196fe49cb8887ac787a6dad
Reviewed-on: https://go-review.googlesource.com/14197
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

7 files changed, 10 insertions, 64 deletions

diff --git a/src/cmd/internal/obj/arm/asm5.go b/src/cmd/internal/obj/arm/asm5.go
index c240e89d46..3bf4a31729 100644
--- a/src/cmd/internal/obj/arm/asm5.go
+++ b/src/cmd/internal/obj/arm/asm5.go
@@ -739,9 +739,6 @@ func span5(ctxt *obj.Link, cursym *obj.LSym) {
 	 * code references to be relocated too, and then
 	 * perhaps we'd be able to parallelize the span loop above.
 	 */
-	if ctxt.Tlsg == nil {
-		ctxt.Tlsg = obj.Linklookup(ctxt, "runtime.tlsg", 0)
-	}
 
 	p = cursym.Text
 	ctxt.Autosize = int32(p.To.Offset + 4)
@@ -1646,19 +1643,7 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
 			rel.Sym = p.To.Sym
 			rel.Add = p.To.Offset
 
-			// runtime.tlsg is special.
-			// Its "address" is the offset from the TLS thread pointer
-			// to the thread-local g and m pointers.
-			// Emit a TLS relocation instead of a standard one if its
-			// type is not explicitly set by runtime. This assumes that
-			// all references to runtime.tlsg should be accompanied with
-			// its type declaration if necessary.
-			if rel.Sym == ctxt.Tlsg && ctxt.Tlsg.Type == 0 {
-				rel.Type = obj.R_TLS
-				if ctxt.Flag_shared != 0 {
-					rel.Add += ctxt.Pc - p.Rel.Pc - 8 - int64(rel.Siz)
-				}
-			} else if ctxt.Flag_shared != 0 {
+			if ctxt.Flag_shared != 0 {
 				rel.Type = obj.R_PCREL
 				rel.Add += ctxt.Pc - p.Rel.Pc - 8
 			} else {
diff --git a/src/cmd/internal/obj/arm/obj5.go b/src/cmd/internal/obj/arm/obj5.go
index d9f587b087..00ab13ccc3 100644
--- a/src/cmd/internal/obj/arm/obj5.go
+++ b/src/cmd/internal/obj/arm/obj5.go
@@ -129,24 +129,6 @@ func progedit(ctxt *obj.Link, p *obj.Prog) {
 			p.From.Offset = 0
 		}
 	}
-
-	if ctxt.Flag_shared != 0 {
-		// Shared libraries use R_ARM_TLS_IE32 instead of
-		// R_ARM_TLS_LE32, replacing the link time constant TLS offset in
-		// runtime.tlsg with an address to a GOT entry containing the
-		// offset. Rewrite $runtime.tlsg(SB) to runtime.tlsg(SB) to
-		// compensate.
-		if ctxt.Tlsg == nil {
-			ctxt.Tlsg = obj.Linklookup(ctxt, "runtime.tlsg", 0)
-		}
-
-		if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && p.From.Sym == ctxt.Tlsg {
-			p.From.Type = obj.TYPE_MEM
-		}
-		if p.To.Type == obj.TYPE_ADDR && p.To.Name == obj.NAME_EXTERN && p.To.Sym == ctxt.Tlsg {
-			p.To.Type = obj.TYPE_MEM
-		}
-	}
 }
 
 // Prog.mark
diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go
index 3a56018985..a78c37e87d 100644
--- a/src/cmd/internal/obj/arm64/asm7.go
+++ b/src/cmd/internal/obj/arm64/asm7.go
@@ -631,9 +631,6 @@ func span7(ctxt *obj.Link, cursym *obj.LSym) {
 	/*
 	 * lay out the code, emitting code and data relocations.
 	 */
-	if ctxt.Tlsg == nil {
-		ctxt.Tlsg = obj.Linklookup(ctxt, "runtime.tlsg", 0)
-	}
 	obj.Symgrow(ctxt, cursym, cursym.Size)
 	bp := cursym.P
 	psz := int32(0)
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 4217d6b0cb..4d6f7d7bdb 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -414,23 +414,16 @@ const (
 	R_CALLPOWER
 	R_CONST
 	R_PCREL
-	// R_TLS (only used on arm currently, and not on android and darwin where tlsg is
-	// a regular variable) resolves to data needed to access the thread-local g. It is
-	// interpreted differently depending on toolchain flags to implement either the
-	// "local exec" or "inital exec" model for tls access.
-	// TODO(mwhudson): change to use R_TLS_LE or R_TLS_IE as appropriate, not having
-	// R_TLS do double duty.
-	R_TLS
-	// R_TLS_LE (only used on 386 and amd64 currently) resolves to the offset of the
-	// thread-local g from the thread local base and is used to implement the "local
-	// exec" model for tls access (r.Sym is not set by the compiler for this case but
-	// is set to Tlsg in the linker when externally linking).
+	// R_TLS_LE, used on 386, amd64, and ARM, resolves to the offset of the
+	// thread-local symbol from the thread local base and is used to implement the
+	// "local exec" model for tls access (r.Sym is not set on intel platforms but is
+	// set to a TLS symbol -- runtime.tlsg -- in the linker when externally linking).
 	R_TLS_LE
-	// R_TLS_IE (only used on 386 and amd64 currently) resolves to the PC-relative
-	// offset to a GOT slot containing the offset the thread-local g from the thread
-	// local base and is used to implemented the "initial exec" model for tls access
-	// (r.Sym is not set by the compiler for this case but is set to Tlsg in the
-	// linker when externally linking).
+	// R_TLS_IE, used 386, amd64, and ARM resolves to the PC-relative offset to a GOT
+	// slot containing the offset from the thread-local symbol from the thread local
+	// base and is used to implemented the "initial exec" model for tls access (r.Sym
+	// is not set on intel platforms but is set to a TLS symbol -- runtime.tlsg -- in
+	// the linker when externally linking).
 	R_TLS_IE
 	R_GOTOFF
 	R_PLT0
@@ -505,7 +498,6 @@ type Link struct {
 	Sym_divu           *LSym
 	Sym_mod            *LSym
 	Sym_modu           *LSym
-	Tlsg               *LSym
 	Plan9privates      *LSym
 	Curp               *Prog
 	Printp             *Prog
diff --git a/src/cmd/internal/obj/mips/asm0.go b/src/cmd/internal/obj/mips/asm0.go
index 2955a0023d..c7498ea5f3 100644
--- a/src/cmd/internal/obj/mips/asm0.go
+++ b/src/cmd/internal/obj/mips/asm0.go
@@ -504,9 +504,6 @@ func span9(ctxt *obj.Link, cursym *obj.LSym) {
 	/*
 	 * lay out the code, emitting code and data relocations.
 	 */
-	if ctxt.Tlsg == nil {
-		ctxt.Tlsg = obj.Linklookup(ctxt, "runtime.tlsg", 0)
-	}
 
 	obj.Symgrow(ctxt, cursym, cursym.Size)
 
diff --git a/src/cmd/internal/obj/ppc64/asm9.go b/src/cmd/internal/obj/ppc64/asm9.go
index 5a1ba9cff2..745da9ef0d 100644
--- a/src/cmd/internal/obj/ppc64/asm9.go
+++ b/src/cmd/internal/obj/ppc64/asm9.go
@@ -504,9 +504,6 @@ func span9(ctxt *obj.Link, cursym *obj.LSym) {
 	/*
 	 * lay out the code, emitting code and data relocations.
 	 */
-	if ctxt.Tlsg == nil {
-		ctxt.Tlsg = obj.Linklookup(ctxt, "runtime.tlsg", 0)
-	}
 
 	obj.Symgrow(ctxt, cursym, cursym.Size)
 
diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go
index e221bdab82..8fbe865219 100644
--- a/src/cmd/internal/obj/x86/obj6.go
+++ b/src/cmd/internal/obj/x86/obj6.go
@@ -435,10 +435,6 @@ func nacladdr(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) {
 }
 
 func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
-	if ctxt.Tlsg == nil {
-		ctxt.Tlsg = obj.Linklookup(ctxt, "runtime.tlsg", 0)
-	}
-
 	if ctxt.Headtype == obj.Hplan9 && ctxt.Plan9privates == nil {
 		ctxt.Plan9privates = obj.Linklookup(ctxt, "_privates", 0)
 	}