runtime: replace is{plan9,solaris,windows} with GOOS tests

Change-Id: I27589395f547c5837dc7536a0ab5bc7cc23a4ff6
Reviewed-on: https://go-review.googlesource.com/10872
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/asm_386.s

@@ -67,13 +67,15 @@ nocpuinfo:
 	MOVL	AX, g_stackguard0(CX)
 	MOVL	AX, g_stackguard1(CX)
 
+#ifndef GOOS_windows
 	// skip runtime·ldt0setup(SB) and tls test after _cgo_init for non-windows
-	CMPL runtime·iswindows(SB), $0
-	JEQ ok
+	JMP ok
+#endif
 needtls:
+#ifdef GOOS_plan9
 	// skip runtime·ldt0setup(SB) and tls test on Plan 9 in all cases
-	CMPL	runtime·isplan9(SB), $1
-	JEQ	ok
+	JMP	ok
+#endif
 
 	// set up %gs
 	CALL	runtime·ldt0setup(SB)

src/runtime/asm_amd64.s

@@ -65,15 +65,18 @@ nocpuinfo:
 	MOVQ	AX, g_stackguard0(CX)
 	MOVQ	AX, g_stackguard1(CX)
 
-	CMPL	runtime·iswindows(SB), $0
-	JEQ ok
+#ifndef GOOS_windows
+	JMP ok
+#endif
 needtls:
+#ifdef GOOS_plan9
 	// skip TLS setup on Plan 9
-	CMPL	runtime·isplan9(SB), $1
-	JEQ ok
+	JMP ok
+#endif
+#ifdef GOOS_solaris
 	// skip TLS setup on Solaris
-	CMPL	runtime·issolaris(SB), $1
-	JEQ ok
+	JMP ok
+#endif
 
 	LEAQ	runtime·tls0(SB), DI
 	CALL	runtime·settls(SB)

src/runtime/rt0_plan9_386.s

@@ -16,8 +16,6 @@ TEXT _rt0_386_plan9(SB),NOSPLIT,$12
 	MOVL	AX, 4(SP)
 	CALL	runtime·rt0_go(SB)
 
-DATA  runtime·isplan9(SB)/4, $1
-GLOBL runtime·isplan9(SB), NOPTR, $4
 GLOBL _tos(SB), NOPTR, $4
 GLOBL _privates(SB), NOPTR, $4
 GLOBL _nprivates(SB), NOPTR, $4

src/runtime/rt0_plan9_amd64.s

@@ -14,8 +14,6 @@ TEXT _rt0_amd64_plan9(SB),NOSPLIT,$24
 	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX
 
-DATA runtime·isplan9(SB)/4, $1
-GLOBL runtime·isplan9(SB), NOPTR, $4
 GLOBL _tos(SB), NOPTR, $8
 GLOBL _privates(SB), NOPTR, $8
 GLOBL _nprivates(SB), NOPTR, $4

src/runtime/rt0_solaris_amd64.s

@@ -13,6 +13,3 @@ TEXT _rt0_amd64_solaris(SB),NOSPLIT,$-8
 TEXT main(SB),NOSPLIT,$-8
 	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX
-
-DATA runtime·issolaris(SB)/4, $1
-GLOBL runtime·issolaris(SB), NOPTR, $4

src/runtime/rt0_windows_386.s

@@ -14,7 +14,3 @@ TEXT _rt0_386_windows(SB),NOSPLIT,$12
 
 TEXT _main(SB),NOSPLIT,$0
 	JMP	runtime·rt0_go(SB)
-
-
-DATA  runtime·iswindows(SB)/4, $1
-GLOBL runtime·iswindows(SB), NOPTR, $4

src/runtime/rt0_windows_amd64.s

@@ -15,6 +15,3 @@ TEXT _rt0_amd64_windows(SB),NOSPLIT,$-8
 TEXT main(SB),NOSPLIT,$-8
 	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX
-
-DATA  runtime·iswindows(SB)/4, $1
-GLOBL runtime·iswindows(SB), NOPTR, $4

src/runtime/runtime1.go

@@ -51,13 +51,6 @@ func args(c int32, v **byte) {
 	sysargs(c, v)
 }
 
-var (
-	// TODO: Retire in favor of GOOS== checks.
-	isplan9   int32
-	issolaris int32
-	iswindows int32
-)
-
 func goargs() {
 	if GOOS == "windows" {
 		return