58 lines
1.9 KiB
Go
58 lines
1.9 KiB
Go
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// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: BSD-3-Clause
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package asm
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import (
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"fmt"
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"strings"
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)
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// This file implements the XSAVE family: the extended-state save and restore
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// pair in its four generations (XSAVE/XRSTOR, XSAVEOPT, XSAVEC, XSAVES) and
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// their 64 spellings. Each takes one memory operand alone; the 64 spellings
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// carry REX.W. Every encoding here is pinned byte for byte against
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// go tool asm through the corpus lines in amd64_xsave_test.go.
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// xsaveSpec is one XSAVE family member: the opcode group and the /digit.
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// XSAVEOPT carries no mandatory prefix in the toolchain's encoding despite
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// the manual's 0x66, so the family has none anywhere.
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type xsaveSpec struct {
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op []byte
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digit int
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}
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// xsaveTable maps the save/restore mnemonics to their encodings. The 64
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// spellings share the base's digit with REX.W.
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var xsaveTable = map[string]xsaveSpec{
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"XSAVE": {[]byte{0x0F, 0xAE}, 4},
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"XRSTOR": {[]byte{0x0F, 0xAE}, 5},
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"XSAVEOPT": {[]byte{0x0F, 0xAE}, 6},
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"XSAVEC": {[]byte{0x0F, 0xC7}, 4},
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"XSAVES": {[]byte{0x0F, 0xC7}, 5},
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"XRSTORS": {[]byte{0x0F, 0xC7}, 3},
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}
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// encodeXsave encodes the XSAVE family. It reports whether the mnemonic
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// belongs to the family.
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func (e *enc) encodeXsave(upper string, ops []Operand) (bool, error) {
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name, rexW := upper, false
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if base, ok := strings.CutSuffix(upper, "64"); ok {
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name, rexW = base, true
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}
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spec, ok := xsaveTable[name]
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if !ok {
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return false, nil
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}
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if len(ops) != 1 {
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return true, fmt.Errorf("%s expects 1 memory operand, got %d", upper, len(ops))
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}
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if !isX86Mem(ops[0]) {
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return true, fmt.Errorf("%s requires a memory operand", upper)
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}
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i := &instr{opcode: append([]byte(nil), spec.op...), modrm: -1, sib: -1, rexW: rexW}
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if err := setRMDigit(i, spec.digit, ops[0], 8); err != nil {
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return true, err
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}
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return true, e.emit(i)
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}
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