feat(asm): encode indirect JMP and CALL on all four architectures

Assisted-by: GLM 5.3 Flash

asm/encode.go

@@ -40,10 +40,20 @@ func (e *enc) encode(mnem string, ops []Operand) error {
 		return e.encodeRet()
 	case upper == "NOP":
 		return e.emit(&instr{opcode: []byte{0x90}, modrm: -1, sib: -1})
-	case upper == "CALL":
-		return e.encodeJmpRel(ops, []byte{0xE8})
-	case upper == "JMP":
-		return e.encodeJmpRel(ops, []byte{0xE9})
+	case upper == "CALL" || upper == "JMP":
+		// Through a register or memory: FF /2 (CALL) or FF /4 (JMP).
+		// Anything else is a rel32 against a label resolved by the assembler.
+		if len(ops) == 1 {
+			switch ops[0].(type) {
+			case Reg, Mem:
+				return e.encodeIndirectBranch(upper, ops)
+			}
+		}
+		opcode := []byte{0xE8}
+		if upper == "JMP" {
+			opcode = []byte{0xE9}
+		}
+		return e.encodeJmpRel(ops, opcode)
 	}
 	if cc, ok := condCode(upper); ok {
 		return e.encodeJcc(cc, ops)