runtime: use correct pipe call for mips/mips64 GNU/Linux

On MIPS, pipe returns two values rather than taking a pointer.

On MIPS64, call pipe2 rather than pipe.

Also, use the correct system call number for fcntl on mips64.

Change-Id: Ie72acdefeb593f44cb98735fc40eac99cf73509e
Reviewed-on: https://go-review.googlesource.com/c/go/+/202417
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/sys_linux_mips64x.s

@@ -19,10 +19,9 @@
 #define SYS_read		5000
 #define SYS_write		5001
 #define SYS_close		5003
-#define SYS_pipe		5021
 #define SYS_getpid		5038
 #define SYS_kill		5060
-#define SYS_fcntl		5080
+#define SYS_fcntl		5070
 #define SYS_mmap		5009
 #define SYS_munmap		5011
 #define SYS_setitimer		5036
@@ -115,7 +114,8 @@ TEXT runtime·read(SB),NOSPLIT|NOFRAME,$0-28
 // func pipe() (r, w int32, errno int32)
 TEXT runtime·pipe(SB),NOSPLIT|NOFRAME,$0-12
 	MOVV	$r+0(FP), R4
-	MOVV	$SYS_pipe, R2
+	MOVV	R0, R5
+	MOVV	$SYS_pipe2, R2
 	SYSCALL
 	MOVW	R2, errno+8(FP)
 	RET

src/runtime/sys_linux_mipsx.s

@@ -112,11 +112,19 @@ TEXT runtime·read(SB),NOSPLIT,$0-16
 
 // func pipe() (r, w int32, errno int32)
 TEXT runtime·pipe(SB),NOSPLIT,$0-12
-	MOVW	$r+0(FP), R4
 	MOVW	$SYS_pipe, R2
 	SYSCALL
+	BEQ	R7, pipeok
+	MOVW	$-1, R1
+	MOVW	R1, r+0(FP)
+	MOVW	R1, w+4(FP)
 	MOVW	R2, errno+8(FP)
 	RET
+pipeok:
+	MOVW	R2, r+0(FP)
+	MOVW	R3, w+4(FP)
+	MOVW	R0, errno+8(FP)
+	RET
 
 // func pipe2(flags int32) (r, w int32, errno int32)
 TEXT runtime·pipe2(SB),NOSPLIT,$0-16