s390x/s390xasm: fix plan9 disassembly regressions on s390x

Regressions were seen in plan9 disassembled syntax on s390x machines.
Raising a CL to fix all of them.

Below are the plan9 syntax regressions noticed:
1) LARL was printed instead of MOVD.
2) Operands for LGDR and LCDBR were printed in a reverse order.
3) MADBR was printed instead of FMADD.
4) VFM was printed instead of WFMDB. Also the mask fields were unnecessarily getting printed.
5) VFS was printed instead of WFSDB. Also the mask fields were unnecessarily getting printed.
6) JMP was printed instead of BR.
7) JMP R14 was printed instead of RET.
8) BRC was printed instead of BVS.

Change-Id: I9166f8ab51ad827bfeeed24a219ceb9b8c41c470
Reviewed-on: https://go-review.googlesource.com/c/arch/+/663756
Reviewed-by: Cherry Mui <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Auto-Submit: Keith Randall <[email protected]>

Author: Vishwanatha-HD

s390x/s390xasm/decode_test.go

@@ -30,15 +30,6 @@ func TestDecode(t *testing.T) {
 	}
 }
 
-// Provide a fake symbol to verify PCrel argument decoding.
-func symlookup(pc uint64) (string, uint64) {
-	foopc := uint64(0x100000)
-	if pc >= foopc && pc < foopc+0x10 {
-		return "foo", foopc
-	}
-	return "", 0
-}
-
 func decode(data []byte, t *testing.T, filename string) {
 	all := string(data)
 	// Simulate PC based on number of instructions found in the test file.

s390x/s390xasm/plan9.go

@@ -142,7 +142,7 @@ func GoSyntax(inst Inst, pc uint64, symname func(uint64) (string, uint64)) strin
 		case LRVH:
 			op = "MOVHBR"
 		}
-	case LA, LAY:
+	case LA, LAY, LARL:
 		args[0], args[1] = args[1], args[0]
 		op = "MOVD"
 
@@ -349,6 +349,17 @@ func GoSyntax(inst Inst, pc uint64, symname func(uint64) (string, uint64)) strin
 	case SLBGR:
 		op = "SUBE"
 		args[0], args[1] = args[1], args[0]
+	case MADBR:
+		op = "FMADD"
+		args[0], args[1], args[2] = args[1], args[2], args[0]
+	case VFM:
+		op = "WFMDB"
+		args[0], args[1], args[2] = args[1], args[2], args[0]
+		args = args[0:3]
+	case VFS:
+		op = "WFSDB"
+		args[0], args[1], args[2] = args[2], args[1], args[0]
+		args = args[0:3]
 	case MSGFR, MHI, MSFI, MSGFI:
 		switch inst.Op {
 		case MSGFR, MHI, MSFI:
@@ -500,16 +511,16 @@ func GoSyntax(inst Inst, pc uint64, symname func(uint64) (string, uint64)) strin
 		if err != nil {
 			return fmt.Sprintf("GoSyntax: error in converting Atoi:%s", err)
 		}
-		opStr, check := branchOnConditionOp(mask, inst.Op)
+		opStr := branchOnConditionOp(mask, inst.Op)
 		if opStr != "" {
 			op = opStr
 		}
 		if op == "SYNC" || op == "NOPH" {
 			return op
 		}
-		if check {
-			args[0] = args[1]
-			args = args[:1]
+		if op == "RET" {
+			args = args[:0]
+			return op
 		}
 	case LOCGR:
 		mask, err := strconv.Atoi(args[2][1:])
@@ -1036,6 +1047,9 @@ func GoSyntax(inst Inst, pc uint64, symname func(uint64) (string, uint64)) strin
 // branch on relative mnemonic.
 func branch_relative_op(mask int, opconst Op) (op string, check bool) {
 	switch mask & 0xf {
+	case 1:
+		op = "BVS"
+		check = true
 	case 2:
 		op = "BGT"
 		check = true
@@ -1061,25 +1075,24 @@ func branch_relative_op(mask int, opconst Op) (op string, check bool) {
 		op = "BLEU"
 		check = true
 	case 15:
-		op = "JMP" // BR
+		op = "BR"
 		check = true
 	}
 	return op, check
 }
 
 // This function returns corresponding extended mnemonic for the given
 // brach on condition mnemonic.
-func branchOnConditionOp(mask int, opconst Op) (op string, check bool) {
+func branchOnConditionOp(mask int, opconst Op) (op string) {
 	switch mask & 0xf {
 	case 0:
 		op = "NOPH"
 	case 14:
 		op = "SYNC"
 	case 15:
-		op = "JMP"
-		check = true
+		op = "RET"
 	}
-	return op, check
+	return op
 }
 
 // This function returns corresponding plan9 mnemonic for the native bitwise mnemonic.
@@ -1260,7 +1273,7 @@ func reverseOperandOrder(op Op) bool {
 	switch op {
 	case LOCR, MLGR:
 		return true
-	case LTEBR, LTDBR:
+	case LTEBR, LTDBR, LCDBR, LGDR:
 		return true
 	case VLEIB, VLEIH, VLEIF, VLEIG, VPDI:
 		return true

s390x/s390xasm/testdata/decode.txt

@@ -14,6 +14,7 @@
     b9e24098|	plan9	MOVDLT R8, R9
     b9e270ba|	plan9	MOVDNE R10, R11
     b9f23012|	plan9	LOCR $3, R2, R1
+    b3130020|	plan9	LCDBR F0, F2
     b9e27065|	plan9	MOVDNE R5, R6
 e310f0000004|	plan9	MOVD (R15), R1
 e320f0000014|	plan9	MOVW (R15), R2
@@ -122,6 +123,13 @@ c017fffffffe|	plan9	XORW $-2, R1
     b93a0008|	plan9	KDSA R0, R8
     b9296024|	plan9	KMA R2, R6, R4
     b92d6024|	plan9	KMCTR R2, R6, R4
+    b31e0042|	plan9	FMADD F4, F2, F0
+e748a00830e7|	plan9	WFMDB V8, V10, V4
+e743000830e2|	plan9	WFSDB V0, V3, V4
+    b3cd0026|	plan9	LGDR F6, R2
+    a7f4008c|	plan9	BR 70(PC)
+    a7140005|	plan9	BVS 2(PC)
+        07fe|	plan9	RET
 e743400000f3|	plan9	VAB V3, V4
 e743600000f3|	plan9	VAB V3, V6, V4
 e743400010f3|	plan9	VAH V3, V4