fix(asm): encode the loong64 64-bit-span 2RI14 offsets like the toolchain

Assisted-by: GLM 5.3

asm/loong64_assemble.go

@@ -825,6 +825,22 @@ func encodeLOONG64Instr(instr *ast.Instr, pc int, offsets map[string]int, fi loo
 		if off&3 != 0 {
 			return nil, fmt.Errorf("%s: offset must be a multiple of 4", mnem)
 		}
+		// The 64-bit span reproduces the toolchain's case 73/74 size-24
+		// expansion word for word, its missing load negation included: a
+		// MOVWP/MOVVP load emits the store opcode, because case 74 spells
+		// opirr(p.As) where the narrower spans spell opirr(-p.As), and the
+		// LL family has no unnegated opirr entry at all, so the toolchain
+		// refuses those loads with "bad irr opcode".
+		if off < -2147483650 || off >= 2147483646 {
+			if load {
+				switch mnem {
+				case "MOVWP", "MOVVP":
+					op += 1 << 24
+				default:
+					return nil, fmt.Errorf("bad irr opcode %s", mnem)
+				}
+			}
+		}
 		return l64firr14Words(op, int(off), rj, rd), nil
 
 	case l64Fir20:
@@ -1292,21 +1308,29 @@ func l64FmaOperands(ops []*ast.Operand) (fa, fk, fj, fd int, err error) {
 // l64MemOperands extracts (rd, rj, off, load) from a load/store instruction:
 // INSTR mem, rd is a load, INSTR rd, mem a store.
 // l64MemOperands splits the two-operand load/store forms: the register and
-// the memory side, the memory's base and byte offset, and the direction.
-func l64MemOperands(ops []*ast.Operand, fi loong64FrameInfo) (rd, rj int, off int32, load bool, err error) {
+// the memory side, the memory's base and full-width byte offset (64-bit
+// offsets reach the 2RI14 families' six-word span), and the direction.
+func l64MemOperands(ops []*ast.Operand, fi loong64FrameInfo) (rd, rj int, off int64, load bool, err error) {
 	if len(ops) != 2 {
 		return 0, 0, 0, false, fmt.Errorf("expected 2 operands, got %d", len(ops))
 	}
+	var mem *ast.Operand
 	if isMemOperand(ops[0]) {
 		rd = l64Reg(ops[1])
-		rj, off = l64MemWithFrame(ops[0], fi)
+		mem = ops[0]
 		load = true
 	} else if isMemOperand(ops[1]) {
 		rd = l64Reg(ops[0])
-		rj, off = l64MemWithFrame(ops[1], fi)
+		mem = ops[1]
 	} else {
 		return 0, 0, 0, false, fmt.Errorf("expected a memory operand")
 	}
+	if mem.Addr.Sym != nil && mem.Addr.Sym.Pseudo != "" {
+		pj, poff := loong64ResolvePseudo(mem.Addr.Sym, fi)
+		rj, off = pj, int64(poff)
+	} else {
+		rj, off = loong64RegNum(mem.Addr.Base), mem.Addr.Offset
+	}
 	if rd < 0 || rj < 0 {
 		return 0, 0, 0, false, fmt.Errorf("invalid operand")
 	}

asm/loong64_encode.go

@@ -264,9 +264,8 @@ func l64WordsLE(ws ...uint32) []byte {
 // a 32-bit one (C_LOREG_32) splits between addu16i.d (bits 31:16, materialised
 // in R30, the assembler temp) and si14 (bits 15:2); anything wider
 // (C_LOREG_64) builds the whole constant in R30 through lu12i.w + ori +
-// lu32i.d + lu52i.d and folds the base into it.  The loong64 backend resolves
-// memory offsets as int32, so the third span answers nothing the encoder can
-// ask today: it stands so the mapping stays complete if that domain widens.
+// lu32i.d + lu52i.d and folds the base into it.  The caller adjusts the
+// opcode for the 64-bit span's load-direction quirks before arriving here.
 func l64firr14Words(op uint32, off, rj, rd int) []byte {
 	switch {
 	case off >= -32766 && off < 32766: