runtime, syscall: in Plan 9 ARM asm, replace "SWI 0" with "SWI $0"

On other systems we use "SWI $n". Change Plan 9 files to be
consistent. Generated binary is unchanged.

Fixes #20378.

Change-Id: Ia2a722061da2450c7b30cb707ed4f172fafecf74
Reviewed-on: https://go-review.googlesource.com/43533Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/sys_plan9_arm.s

@@ -54,21 +54,21 @@
 //func open(name *byte, mode, perm int32) int32
 TEXT runtime·open(SB),NOSPLIT,$0-16
 	MOVW    $SYS_OPEN, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+12(FP)
 	RET
 
 //func pread(fd int32, buf unsafe.Pointer, nbytes int32, offset int64) int32
 TEXT runtime·pread(SB),NOSPLIT,$0-24
 	MOVW    $SYS_PREAD, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+20(FP)
 	RET
 
 //func pwrite(fd int32, buf unsafe.Pointer, nbytes int32, offset int64) int32
 TEXT runtime·pwrite(SB),NOSPLIT,$0-24
 	MOVW    $SYS_PWRITE, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+20(FP)
 	RET
 
@@ -79,7 +79,7 @@ TEXT runtime·seek(SB),NOSPLIT,$0-24
 	MOVW	R0, 0(R13)
 	MOVW.W	R1, -4(R13)
 	MOVW	$SYS_SEEK, R0
-	SWI	0
+	SWI	$0
 	MOVW.W	R1, 4(R13)
 	CMP	$-1, R0
 	MOVW.EQ	R0, ret_lo+16(FP)
@@ -89,48 +89,48 @@ TEXT runtime·seek(SB),NOSPLIT,$0-24
 //func closefd(fd int32) int32
 TEXT runtime·closefd(SB),NOSPLIT,$0-8
 	MOVW	$SYS_CLOSE, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+4(FP)
 	RET
 
 //func exits(msg *byte)
 TEXT runtime·exits(SB),NOSPLIT,$0-4
 	MOVW    $SYS_EXITS, R0
-	SWI	0
+	SWI	$0
 	RET
 
 //func brk_(addr unsafe.Pointer) int32
 TEXT runtime·brk_(SB),NOSPLIT,$0-8
 	MOVW    $SYS_BRK_, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+4(FP)
 	RET
 
 //func sleep(ms int32) int32
 TEXT runtime·sleep(SB),NOSPLIT,$0-8
 	MOVW    $SYS_SLEEP, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+4(FP)
 	RET
 
 //func plan9_semacquire(addr *uint32, block int32) int32
 TEXT runtime·plan9_semacquire(SB),NOSPLIT,$0-12
 	MOVW	$SYS_SEMACQUIRE, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+8(FP)
 	RET
 
 //func plan9_tsemacquire(addr *uint32, ms int32) int32
 TEXT runtime·plan9_tsemacquire(SB),NOSPLIT,$0-12
 	MOVW	$SYS_TSEMACQUIRE, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+8(FP)
 	RET
 
 //func nsec(*int64) int64
 TEXT runtime·nsec(SB),NOSPLIT,$-4-12
 	MOVW	$SYS_NSEC, R0
-	SWI	0
+	SWI	$0
 	MOVW	arg+0(FP), R1
 	MOVW	0(R1), R0
 	MOVW	R0, ret_lo+4(FP)
@@ -144,7 +144,7 @@ TEXT runtime·walltime(SB),NOSPLIT,$12-12
 	MOVW	$sysnsec_lo-8(SP), R0	// destination addr
 	MOVW	R0,res-12(SP)
 	MOVW	$SYS_NSEC, R0
-	SWI	0
+	SWI	$0
 	MOVW	sysnsec_lo-8(SP), R1	// R1:R2 = nsec
 	MOVW	sysnsec_hi-4(SP), R2
 
@@ -181,28 +181,28 @@ TEXT runtime·walltime(SB),NOSPLIT,$12-12
 //func notify(fn unsafe.Pointer) int32
 TEXT runtime·notify(SB),NOSPLIT,$0-8
 	MOVW	$SYS_NOTIFY, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+4(FP)
 	RET
 
 //func noted(mode int32) int32
 TEXT runtime·noted(SB),NOSPLIT,$0-8
 	MOVW	$SYS_NOTED, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+4(FP)
 	RET
 
 //func plan9_semrelease(addr *uint32, count int32) int32
 TEXT runtime·plan9_semrelease(SB),NOSPLIT,$0-12
 	MOVW	$SYS_SEMRELEASE, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+8(FP)
 	RET
 
 //func rfork(flags int32) int32
 TEXT runtime·rfork(SB),NOSPLIT,$0-8
 	MOVW	$SYS_RFORK, R0
-	SWI	0
+	SWI	$0
 	MOVW	R0, ret+4(FP)
 	RET
 
@@ -297,7 +297,7 @@ TEXT runtime·errstr(SB),NOSPLIT,$0-8
 	MOVW	$ERRMAX, R2
 	MOVW	R2, ret_len+4(FP)
 	MOVW    $SYS_ERRSTR, R0
-	SWI	0
+	SWI	$0
 	MOVW	R1, R2
 	MOVBU	0(R2), R0
 	CMP	$0, R0

src/syscall/asm_plan9_arm.s

@@ -27,7 +27,7 @@ TEXT	·Syscall(SB),NOSPLIT,$0-32
 	BL		runtime·entersyscall(SB)
 	MOVW	trap+0(FP), R0	// syscall num
 	MOVM.IA.W	(R13),[R1-R2]	// pop LR and caller's LR
-	SWI		0
+	SWI		$0
 	MOVM.DB.W	[R1-R2],(R13)	// push LR and caller's LR
 	MOVW	$0, R2
 	MOVW	$r1+16(FP), R1
@@ -42,7 +42,7 @@ TEXT	·Syscall6(SB),NOSPLIT,$0-44
 	BL		runtime·entersyscall(SB)
 	MOVW	trap+0(FP), R0	// syscall num
 	MOVM.IA.W	(R13),[R1-R2]	// pop LR and caller's LR
-	SWI		0
+	SWI		$0
 	MOVM.DB.W	[R1-R2],(R13)	// push LR and caller's LR
 	MOVW	$0, R1
 	MOVW	$r1+28(FP), R1
@@ -55,7 +55,7 @@ TEXT	·Syscall6(SB),NOSPLIT,$0-44
 TEXT ·RawSyscall(SB),NOSPLIT,$0-28
 	MOVW	trap+0(FP), R0	// syscall num
 	MOVM.IA.W	(R13),[R1]		// pop caller's LR
-	SWI		0
+	SWI		$0
 	MOVM.DB.W	[R1],(R13)		// push caller's LR
 	MOVW	R0, r1+16(FP)
 	MOVW	R0, r2+20(FP)
@@ -67,7 +67,7 @@ TEXT ·RawSyscall(SB),NOSPLIT,$0-28
 TEXT	·RawSyscall6(SB),NOSPLIT,$0-40
 	MOVW	trap+0(FP), R0	// syscall num
 	MOVM.IA.W	(R13),[R1]		// pop caller's LR
-	SWI		0
+	SWI		$0
 	MOVM.DB.W	[R1],(R13)		// push caller's LR
 	MOVW	R0, r1+28(FP)
 	MOVW	R0, r2+32(FP)
@@ -80,7 +80,7 @@ TEXT ·seek(SB),NOSPLIT,$0-36
 	MOVW	R5, placeholder+0(FP)	//placeholder = dest for return value
 	MOVW	$SYS_SEEK, R0		// syscall num
 	MOVM.IA.W	(R13),[R1]		// pop LR
-	SWI		0
+	SWI		$0
 	MOVM.DB.W	[R1],(R13)		// push LR
 	CMP		$-1, R0
 	MOVW.EQ	R0, 0(R5)