cmd/asm, runtime: remove the RSB register from loong64

It was carryover from the mips64 port (where it represented the platform
GP register) but LoongArch platform ABI doesn't have the GP concept.

Change-Id: Iea326ae13676e95b040b52aaadc08d311b507bd3
Reviewed-on: https://go-review.googlesource.com/c/go/+/475815
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

src/cmd/asm/internal/arch/arch.go

@@ -536,7 +536,6 @@ func archLoong64(linkArch *obj.LinkArch) *Arch {
 	// Avoid unintentionally clobbering g using R22.
 	delete(register, "R22")
 	register["g"] = loong64.REG_R22
-	register["RSB"] = loong64.REG_R31
 	registerPrefix := map[string]bool{
 		"F":    true,
 		"FCSR": true,

src/cmd/asm/internal/asm/operand_test.go

@@ -915,8 +915,9 @@ var loong64OperandTests = []operandTest{
 	{"R27", "R27"},
 	{"R28", "R28"},
 	{"R29", "R29"},
-	{"R30", "R30"},
 	{"R3", "R3"},
+	{"R30", "R30"},
+	{"R31", "R31"},
 	{"R4", "R4"},
 	{"R5", "R5"},
 	{"R6", "R6"},
@@ -925,7 +926,6 @@ var loong64OperandTests = []operandTest{
 	{"R9", "R9"},
 	{"a(FP)", "a(FP)"},
 	{"g", "g"},
-	{"RSB", "R31"},
 	{"ret+8(FP)", "ret+8(FP)"},
 	{"runtime·abort(SB)", "runtime.abort(SB)"},
 	{"·AddUint32(SB)", "\"\".AddUint32(SB)"},

src/runtime/mkpreempt.go

@@ -462,20 +462,18 @@ func genLoong64() {
 	movf := "MOVD"
 	add := "ADDV"
 	sub := "SUBV"
-	r31 := "RSB"
 	regsize := 8
 
 	// Add integer registers r4-r21 r23-r29 r31
 	// R0 (zero), R30 (REGTMP), R2 (tp), R3 (SP), R22 (g), R1 (LR) are special,
 	var l = layout{sp: "R3", stack: regsize} // add slot to save PC of interrupted instruction (in LR)
-	for i := 4; i <= 29; i++ {
-		if i == 22 {
-			continue // R3 is REGSP  R22 is g
+	for i := 4; i <= 31; i++ {
+		if i == 22 || i == 30 {
+			continue
 		}
 		reg := fmt.Sprintf("R%d", i)
 		l.add(mov, reg, regsize)
 	}
-	l.add(mov, r31, regsize)
 
 	// Add floating point registers F0-F31.
 	for i := 0; i <= 31; i++ {

src/runtime/preempt_loong64.s

@@ -31,7 +31,7 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	MOVV R27, 184(R3)
 	MOVV R28, 192(R3)
 	MOVV R29, 200(R3)
-	MOVV RSB, 208(R3)
+	MOVV R31, 208(R3)
 	MOVD F0, 216(R3)
 	MOVD F1, 224(R3)
 	MOVD F2, 232(R3)
@@ -97,7 +97,7 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	MOVD 232(R3), F2
 	MOVD 224(R3), F1
 	MOVD 216(R3), F0
-	MOVV 208(R3), RSB
+	MOVV 208(R3), R31
 	MOVV 200(R3), R29
 	MOVV 192(R3), R28
 	MOVV 184(R3), R27

src/runtime/signal_loong64.go

@@ -77,10 +77,8 @@ func (c *sigctxt) preparePanic(sig uint32, gp *g) {
 	}
 
 	// In case we are panicking from external C code
-	sigpanicPC := uint64(abi.FuncPCABIInternal(sigpanic))
-	c.set_r31(sigpanicPC >> 32 << 32) // RSB register
 	c.set_r22(uint64(uintptr(unsafe.Pointer(gp))))
-	c.set_pc(sigpanicPC)
+	c.set_pc(uint64(abi.FuncPCABIInternal(sigpanic)))
 }
 
 func (c *sigctxt) pushCall(targetPC, resumePC uintptr) {