feat(asm): emit the loong64 stack-split guard for small and medium frames

asm/goobjloong64.go

@@ -25,11 +25,16 @@ func (img *Image) GOObjectLOONG64(pkgPath, srcPath string) ([]byte, error) {
 	}
 	return img.emitGOObject(pkgPath, srcPath, pre, 4, func(r Reloc) (uint16, uint8) {
 		// A pcalau12i+addi.d pair: the high part carries
-		// R_LOONG64_ADDR_HI, the low part R_LOONG64_ADDR_LO.
-		if r.Kind == RelLoong64AddrLo {
+		// R_LOONG64_ADDR_HI, the low part R_LOONG64_ADDR_LO; the guard's
+		// morestack call carries R_CALLLOONG64.
+		switch {
+		case r.Kind == RelLoong64AddrLo:
 			return relocLoong64AddrLo, 4
+		case r.Kind == RelLoong64Branch:
+			return relocCallLoong64, 4
+		default:
+			return relocLoong64AddrHi, 4
 		}
-		return relocLoong64AddrHi, 4
 	})
 }
 
@@ -39,6 +44,7 @@ func (img *Image) GOObjectLOONG64(pkgPath, srcPath string) ([]byte, error) {
 const (
 	relocLoong64AddrHi = 77 // R_LOONG64_ADDR_HI
 	relocLoong64AddrLo = 78 // R_LOONG64_ADDR_LO
+	relocCallLoong64   = 84 // R_CALLLOONG64
 )
 
 // toolchainObjectPreambleLOONG64 returns the "go object ...\n!\n" header