// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

package disasm

import "fmt"

// golang.org/x/arch refuses a corner of the arm64 exception-generation
// space outright: the hypervisor call HVC, the secure monitor call SMC and
// the speculation barrier SB.  The toolchain's assembler corpus carries all
// three with machine-checked encodings (arm64enc.s's "HVC $61428 //
// 82fe1dd4" and its kin), so the disassembler names them from the raw word
// in the error branch, the way the amd64 table does.
//
// The encodings are the exception space 1101 0100 0 opc imm16 op2: HVC is
// opc 000 with the op2 marker 00010, SMC the same opc with 00011, and SB
// the fixed barrier word 0xD50330FF.  Every other shape in the space keeps
// the placeholder.

// nameARM64Rejected names an arm64 word the decoder refuses.  It reports
// the rendered text, the instruction's length in bytes and whether the word
// matched a family; a non-match keeps the placeholder.
func nameARM64Rejected(code []byte) (string, int, bool) {
	w := uint32(code[0]) | uint32(code[1])<<8 | uint32(code[2])<<16 | uint32(code[3])<<24
	switch {
	case w == 0xd50330ff:
		return "SB", 4, true
	case w>>21 == 0x6a0:
		imm := (w >> 5) & 0xffff
		switch w & 0x1f {
		case 0x02:
			return fmt.Sprintf("HVC $%d", imm), 4, true
		case 0x03:
			return fmt.Sprintf("SMC $%d", imm), 4, true
		}
	}
	return "", 0, false
}