src/math/big/internal/asmgen/386.go

// Copyright 2025 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package asmgen

import "fmt"

var Arch386 = &Arch{
	Name:      "386",
	WordBits:  32,
	WordBytes: 4,

	regs: []string{
		"BX", "SI", "DI", "BP",
		"CX", "DX", "AX", // last, to leave available for hinted allocation
	},
	op3:              x86Op3,
	hint:             x86Hint,
	memOK:            true,
	subCarryIsBorrow: true,
	maxColumns:       1, // not enough registers for more

	// Note: It would be nice to not set memIndex and then
	// delete all the code in pipe.go that supports it.
	// But a few routines, notably lshVU and mulAddVWW,
	// benefit dramatically from the use of index registers.
	// Perhaps some day we will decide 386 performance
	// does not matter enough to keep this code.
	memIndex: _386MemIndex,

	mov:      "MOVL",
	adds:     "ADDL",
	adcs:     "ADCL",
	subs:     "SUBL",
	sbcs:     "SBBL",
	lsh:      "SHLL",
	lshd:     "SHLL",
	rsh:      "SHRL",
	rshd:     "SHRL",
	and:      "ANDL",
	or:       "ORL",
	xor:      "XORL",
	neg:      "NEGL",
	lea:      "LEAL",
	mulWideF: x86MulWide,

	addWords: "LEAL (%[2]s)(%[1]s*4), %[3]s",

	jmpZero:       "TESTL %[1]s, %[1]s; JZ %[2]s",
	jmpNonZero:    "TESTL %[1]s, %[1]s; JNZ %[2]s",
	loopBottom:    "SUBL $1, %[1]s; JNZ %[2]s",
	loopBottomNeg: "ADDL $1, %[1]s; JNZ %[2]s",
}

func _386MemIndex(a *Asm, off int, ix Reg, p RegPtr) Reg {
	return Reg{fmt.Sprintf("%d(%s)(%s*%d)", off, p, ix, a.Arch.WordBytes)}
}