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

Assisted-by: GLM 5.3 Flash

asm/loong64_assemble.go

@@ -6,6 +6,7 @@ package asm
 import (
 	"fmt"
 	"math/bits"
+	"strconv"
 	"strings"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
@@ -258,6 +259,9 @@ func encodeLOONG64Instr(instr *ast.Instr, pc int, offsets map[string]int, fi loo
 
 	// 16-bit branches (BEQ/BNE/BLT/BGE/BLTU/BGEU) and JIRL.
 	if op, ok := l64branchTable[mnem]; ok {
+		if mnem == "JIRL" {
+			return encodeLOONG64Jirl(op, ops)
+		}
 		return encodeLOONG64Branch16(mnem, op, ops, pc, offsets, resolve)
 	}
 	// Single-register branches with 21-bit offsets (BLTZ/BGEZ/BLEZ/BGTZ,
@@ -554,6 +558,46 @@ func encodeLOONG64Branch(instr *ast.Instr, mnem string, pc int, offsets map[stri
 	return l64wordLE(l64bbl(opc, v)), nil
 }
 
+// encodeLOONG64Jirl encodes the raw JIRL spelling, JIRL rd, rj, offset, the
+// form the verify trampolines use.  The (rj) indirect form without an offset
+// is handled by encodeLOONG64Branch.
+func encodeLOONG64Jirl(op uint32, ops []*ast.Operand) ([]byte, error) {
+	if len(ops) != 3 {
+		return nil, fmt.Errorf("JIRL expects 3 operands, got %d", len(ops))
+	}
+	rd := l64Reg(ops[0])
+	rj := l64Reg(ops[1])
+	if rd < 0 || rj < 0 {
+		return nil, fmt.Errorf("invalid register operand")
+	}
+	off, ok := l64offsetOperand(ops[2])
+	if !ok {
+		return nil, fmt.Errorf("JIRL expects an immediate offset, got %q", ops[2].Raw)
+	}
+	if (int64(off)<<16)>>16 != int64(off) {
+		return nil, fmt.Errorf("JIRL offset %d out of the 16-bit range", off)
+	}
+	return l64wordLE(l64irr16(op, int(off), rj, rd)), nil
+}
+
+// l64offsetOperand reads a bare numeric branch offset: an immediate ($n) or a
+// plain number, which parses as an empty address carrying the digits in Raw.
+func l64offsetOperand(op *ast.Operand) (int32, bool) {
+	if op.Imm.HasVal {
+		v := op.Imm.Val
+		if op.Imm.Neg {
+			v = -v
+		}
+		return int32(v), true
+	}
+	if op.Kind == ast.OpAddr && op.Addr.Sym == nil && op.Addr.Base == "" && op.Addr.Index == "" {
+		if v, err := strconv.ParseInt(op.Raw, 0, 64); err == nil {
+			return int32(v), true
+		}
+	}
+	return 0, false
+}
+
 // encodeLOONG64Branch16 encodes a 16-bit branch (BEQ/BNE/BLT/BGE/BLTU/BGEU):
 // INSTR rj, rd, label, or INSTR rj, label with rd = R0, which the toolchain
 // turns into the 21-bit BEQZ/BNEZ form when the register is the only operand.