runtime: replace tls0 with m0.tls

We're allocating TLS storage for m0 anyway, so might as well use it.

Change-Id: I7dc20bbea5320c8ab8a367f18a9540706751e771
Reviewed-on: https://go-review.googlesource.com/16890
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/asm_386.s

@@ -83,7 +83,7 @@ needtls:
 	// store through it, to make sure it works
 	get_tls(BX)
 	MOVL	$0x123, g(BX)
-	MOVL	runtime·tls0(SB), AX
+	MOVL	runtime·m0+m_tls(SB), AX
 	CMPL	AX, $0x123
 	JEQ	ok
 	MOVL	AX, 0	// abort
@@ -765,11 +765,11 @@ done:
 	RET
 
 TEXT runtime·ldt0setup(SB),NOSPLIT,$16-0
-	// set up ldt 7 to point at tls0
+	// set up ldt 7 to point at m0.tls
 	// ldt 1 would be fine on Linux, but on OS X, 7 is as low as we can go.
 	// the entry number is just a hint.  setldt will set up GS with what it used.
 	MOVL	$7, 0(SP)
-	LEAL	runtime·tls0(SB), AX
+	LEAL	runtime·m0+m_tls(SB), AX
 	MOVL	AX, 4(SP)
 	MOVL	$32, 8(SP)	// sizeof(tls array)
 	CALL	runtime·setldt(SB)

src/runtime/asm_amd64.s

@@ -104,13 +104,13 @@ needtls:
 	JMP ok
 #endif
 
-	LEAQ	runtime·tls0(SB), DI
+	LEAQ	runtime·m0+m_tls(SB), DI
 	CALL	runtime·settls(SB)
 
 	// store through it, to make sure it works
 	get_tls(BX)
 	MOVQ	$0x123, g(BX)
-	MOVQ	runtime·tls0(SB), AX
+	MOVQ	runtime·m0+m_tls(SB), AX
 	CMPQ	AX, $0x123
 	JEQ 2(PC)
 	MOVL	AX, 0	// abort

src/runtime/asm_amd64p32.s

@@ -39,13 +39,13 @@ TEXT runtime·rt0_go(SB),NOSPLIT,$0
 nocpuinfo:	
 	
 needtls:
-	LEAL	runtime·tls0(SB), DI
+	LEAL	runtime·m0+m_tls(SB), DI
 	CALL	runtime·settls(SB)
 
 	// store through it, to make sure it works
 	get_tls(BX)
 	MOVQ	$0x123, g(BX)
-	MOVQ	runtime·tls0(SB), AX
+	MOVQ	runtime·m0+m_tls(SB), AX
 	CMPQ	AX, $0x123
 	JEQ 2(PC)
 	MOVL	AX, 0	// abort

src/runtime/os1_windows.go

@@ -577,9 +577,6 @@ func profilem(mp *m) {
 	rbuf := make([]byte, unsafe.Sizeof(*r)+15)
 
 	tls := &mp.tls[0]
-	if mp == &m0 {
-		tls = &tls0[0]
-	}
 	gp := *((**g)(unsafe.Pointer(tls)))
 
 	// align Context to 16 bytes

src/runtime/rt0_linux_ppc64le.s

+#include "go_asm.h"
 #include "textflag.h"
 
 TEXT _rt0_ppc64le_linux(SB),NOSPLIT,$0
@@ -22,7 +23,7 @@ TEXT _main<>(SB),NOSPLIT,$-8
 	// Statically linked
 	MOVD	0(R1), R3 // argc
 	ADD	$8, R1, R4 // argv
-	MOVD	$runtime·tls0(SB), R13 // TLS
+	MOVD	$runtime·m0+m_tls(SB), R13 // TLS
 	ADD	$0x7000, R13
 
 dlink:

src/runtime/runtime.go

@@ -19,8 +19,6 @@ var ticks struct {
 	val  uint64
 }
 
-var tls0 [8]uintptr // available storage for m0's TLS; not necessarily used; opaque to GC
-
 // Note: Called by runtime/pprof in addition to runtime code.
 func tickspersecond() int64 {
 	r := int64(atomic.Load64(&ticks.val))