cmd/internal/obj/s390x: add support of SPM instruction

For restoring condition code (we already support IPM instruction
for saving condition code).

Change-Id: I56d376df44a5f831134a130d052521cec6b5b781
Reviewed-on: https://go-review.googlesource.com/c/go/+/204104Reviewed-by: Michael Munday <mike.munday@ibm.com>

src/cmd/asm/internal/asm/testdata/s390x.s

@@ -284,6 +284,9 @@ TEXT main·foo(SB),DUPOK|NOSPLIT,$16-0 // TEXT main.foo(SB), DUPOK|NOSPLIT, $16-
 	IPM	R3                     // b2220030
 	IPM	R12                    // b22200c0
 
+	SPM	R1                     // 0410
+	SPM	R10                    // 04a0
+
 	BRC	$7, 0(PC)              // a7740000
 	BNE	0(PC)                  // a7740000
 	BEQ	0(PC)                  // a7840000

src/cmd/internal/obj/s390x/a.out.go

@@ -386,6 +386,9 @@ const (
 	// insert program mask
 	AIPM
 
+	// set program mask
+	ASPM
+
 	// compare and swap
 	ACS
 	ACSG

src/cmd/internal/obj/s390x/anames.go

@@ -138,6 +138,7 @@ var Anames = []string{
 	"TMLH",
 	"TMLL",
 	"IPM",
+	"SPM",
 	"CS",
 	"CSG",
 	"SYNC",

src/cmd/internal/obj/s390x/asmz.go

@@ -286,6 +286,9 @@ var optab = []Optab{
 	// insert program mask
 	{i: 92, as: AIPM, a1: C_REG},
 
+	// set program mask
+	{i: 76, as: ASPM, a1: C_REG},
+
 	// 32-bit access registers
 	{i: 68, as: AMOVW, a1: C_AREG, a6: C_REG},
 	{i: 68, as: AMOVWZ, a1: C_AREG, a6: C_REG},
@@ -3630,6 +3633,9 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 		}
 		c.addrilreloc(p.From.Sym, int64(i2))
 
+	case 76: // set program mask
+		zRR(op_SPM, uint32(p.From.Reg), 0, asm)
+
 	case 77: // syscall $constant
 		if p.From.Offset > 255 || p.From.Offset < 1 {
 			c.ctxt.Diag("illegal system call; system call number out of range: %v", p)