cmd/asm: add masked branch and conditional load instructions to s390x

The branch-relative-on-condition (BRC) instruction allows us to use
an immediate to specify under what conditions the branch is taken.
For example, `BRC $7, L1` is equivalent to `BNE L1`. It is sometimes
useful to specify branches in this way when either we don't have
an extended mnemonic for a particular mask value or we want to
generate the condition code mask programmatically.

The new load-on-condition (LOCR and LOCGR) and compare-and-branch
(CRJ, CGRJ, CLRJ, CLGRJ, CIJ, CGIJ, CLIJ and CLGIJ) instructions
provide the same flexibility for conditional loads and combined
compare and branch instructions.

Change-Id: Ic6f5d399b0157e278b39bd3645f4ee0f4df8e5fc
Reviewed-on: https://go-review.googlesource.com/c/go/+/196558
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

3 files changed, 37 insertions, 3 deletions

diff --git a/src/cmd/asm/internal/arch/s390x.go b/src/cmd/asm/internal/arch/s390x.go
index d6d46f86f2..6efae26e1c 100644
--- a/src/cmd/asm/internal/arch/s390x.go
+++ b/src/cmd/asm/internal/arch/s390x.go
@@ -15,7 +15,8 @@ import (
 
 func jumpS390x(word string) bool {
 	switch word {
-	case "BC",
+	case "BRC",
+		"BC",
 		"BCL",
 		"BEQ",
 		"BGE",
@@ -41,6 +42,14 @@ func jumpS390x(word string) bool {
 		"CMPUBLE",
 		"CMPUBLT",
 		"CMPUBNE",
+		"CRJ",
+		"CGRJ",
+		"CLRJ",
+		"CLGRJ",
+		"CIJ",
+		"CGIJ",
+		"CLIJ",
+		"CLGIJ",
 		"CALL",
 		"JMP":
 		return true
diff --git a/src/cmd/asm/internal/asm/asm.go b/src/cmd/asm/internal/asm/asm.go
index c6f07832a7..26b355dee1 100644
--- a/src/cmd/asm/internal/asm/asm.go
+++ b/src/cmd/asm/internal/asm/asm.go
@@ -450,8 +450,19 @@ func (p *Parser) asmJump(op obj.As, cond string, a []obj.Addr) {
 			target = &a[2]
 			break
 		}
-
-		fallthrough
+		p.errorf("wrong number of arguments to %s instruction", op)
+		return
+	case 4:
+		if p.arch.Family == sys.S390X {
+			// 4-operand compare-and-branch.
+			prog.From = a[0]
+			prog.Reg = p.getRegister(prog, op, &a[1])
+			prog.SetFrom3(a[2])
+			target = &a[3]
+			break
+		}
+		p.errorf("wrong number of arguments to %s instruction", op)
+		return
 	default:
 		p.errorf("wrong number of arguments to %s instruction", op)
 		return
diff --git a/src/cmd/asm/internal/asm/testdata/s390x.s b/src/cmd/asm/internal/asm/testdata/s390x.s
index 62563d885e..4fc599416f 100644
--- a/src/cmd/asm/internal/asm/testdata/s390x.s
+++ b/src/cmd/asm/internal/asm/testdata/s390x.s
@@ -22,6 +22,9 @@ TEXT main·foo(SB),DUPOK|NOSPLIT,$16-0 // TEXT main.foo(SB), DUPOK|NOSPLIT, $16-
 	MOVDLT	R8, R9                // b9e24098
 	MOVDNE	R10, R11              // b9e270ba
 
+	LOCR	$3, R2, R1            // b9f23012
+	LOCGR	$7, R5, R6            // b9e27065
+
 	MOVD	(R15), R1             // e310f0000004
 	MOVW	(R15), R2             // e320f0000014
 	MOVH	(R15), R3             // e330f0000015
@@ -253,6 +256,7 @@ TEXT main·foo(SB),DUPOK|NOSPLIT,$16-0 // TEXT main.foo(SB), DUPOK|NOSPLIT, $16-
 	IPM	R3                     // b2220030
 	IPM	R12                    // b22200c0
 
+	BRC	$7, 0(PC)              // a7740000
 	BNE	0(PC)                  // a7740000
 	BEQ	0(PC)                  // a7840000
 	BLT	0(PC)                  // a7440000
@@ -290,6 +294,16 @@ TEXT main·foo(SB),DUPOK|NOSPLIT,$16-0 // TEXT main.foo(SB), DUPOK|NOSPLIT, $16-
 	CMPUBGT	R9, $256, 0(PC)        // ec920000007d
 	CMPUBGE	R2, $0, 0(PC)          // ec2a0000007d
 
+	CRJ	$15, R1, R2, 0(PC)     // ec120000f076
+	CGRJ	$12, R3, R4, 0(PC)     // ec340000c064
+	CLRJ	$3, R5, R6, 0(PC)      // ec5600003077
+	CLGRJ	$0, R7, R8, 0(PC)      // ec7800000065
+
+	CIJ	$4, R9, $127, 0(PC)    // ec9400007f7e
+	CGIJ	$8, R11, $-128, 0(PC)  // ecb80000807c
+	CLIJ	$1, R1, $255, 0(PC)    // ec110000ff7f
+	CLGIJ	$2, R3, $0, 0(PC)      // ec320000007d
+
 	LGDR	F1, R12                // b3cd00c1
 	LDGR	R2, F15                // b3c100f2