386.go

     1  // Copyright 2025 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package asmgen
     6  
     7  import "fmt"
     8  
     9  var Arch386 = &Arch{
    10  	Name:      "386",
    11  	WordBits:  32,
    12  	WordBytes: 4,
    13  
    14  	regs: []string{
    15  		"BX", "SI", "DI", "BP",
    16  		"CX", "DX", "AX", // last, to leave available for hinted allocation
    17  	},
    18  	op3:              x86Op3,
    19  	hint:             x86Hint,
    20  	memOK:            true,
    21  	subCarryIsBorrow: true,
    22  	maxColumns:       1, // not enough registers for more
    23  
    24  	// Note: It would be nice to not set memIndex and then
    25  	// delete all the code in pipe.go that supports it.
    26  	// But a few routines, notably lshVU and mulAddVWW,
    27  	// benefit dramatically from the use of index registers.
    28  	// Perhaps some day we will decide 386 performance
    29  	// does not matter enough to keep this code.
    30  	memIndex: _386MemIndex,
    31  
    32  	mov:      "MOVL",
    33  	adds:     "ADDL",
    34  	adcs:     "ADCL",
    35  	subs:     "SUBL",
    36  	sbcs:     "SBBL",
    37  	lsh:      "SHLL",
    38  	lshd:     "SHLL",
    39  	rsh:      "SHRL",
    40  	rshd:     "SHRL",
    41  	and:      "ANDL",
    42  	or:       "ORL",
    43  	xor:      "XORL",
    44  	neg:      "NEGL",
    45  	lea:      "LEAL",
    46  	mulWideF: x86MulWide,
    47  
    48  	addWords: "LEAL (%[2]s)(%[1]s*4), %[3]s",
    49  
    50  	jmpZero:       "TESTL %[1]s, %[1]s; JZ %[2]s",
    51  	jmpNonZero:    "TESTL %[1]s, %[1]s; JNZ %[2]s",
    52  	loopBottom:    "SUBL $1, %[1]s; JNZ %[2]s",
    53  	loopBottomNeg: "ADDL $1, %[1]s; JNZ %[2]s",
    54  }
    55  
    56  func _386MemIndex(a *Asm, off int, ix Reg, p RegPtr) Reg {
    57  	return Reg{fmt.Sprintf("%d(%s)(%s*%d)", off, p, ix, a.Arch.WordBytes)}
    58  }
    59
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