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package printer
import (
"strconv"
"strings"
"github.com/mmcloughlin/avo/buildtags"
"github.com/mmcloughlin/avo/internal/prnt"
"github.com/mmcloughlin/avo/ir"
"github.com/mmcloughlin/avo/operand"
)
// dot is the pesky unicode dot used in Go assembly.
const dot = "\u00b7"
type goasm struct {
cfg Config
prnt.Generator
instructions []*ir.Instruction
clear bool
}
// NewGoAsm constructs a printer for writing Go assembly files.
func NewGoAsm(cfg Config) Printer {
return &goasm{cfg: cfg}
}
func (p *goasm) Print(f *ir.File) ([]byte, error) {
p.header(f)
for _, s := range f.Sections {
switch s := s.(type) {
case *ir.Function:
p.function(s)
case *ir.Global:
p.global(s)
default:
panic("unknown section type")
}
}
return p.Result()
}
func (p *goasm) header(f *ir.File) {
p.Comment(p.cfg.GeneratedWarning())
if len(f.Constraints) > 0 {
constraints, err := buildtags.Format(f.Constraints)
if err != nil {
p.AddError(err)
}
p.NL()
p.Printf(constraints)
}
if len(f.Includes) > 0 {
p.NL()
p.includes(f.Includes)
}
}
func (p *goasm) includes(paths []string) {
for _, path := range paths {
p.Printf("#include \"%s\"\n", path)
}
}
func (p *goasm) function(f *ir.Function) {
p.NL()
p.Comment(f.Stub())
if len(f.ISA) > 0 {
p.Comment("Requires: " + strings.Join(f.ISA, ", "))
}
// Reference: https://github.com/golang/go/blob/b115207baf6c2decc3820ada4574ef4e5ad940ec/src/cmd/internal/obj/util.go#L166-L176
//
// if p.As == ATEXT {
// // If there are attributes, print them. Otherwise, skip the comma.
// // In short, print one of these two:
// // TEXT foo(SB), DUPOK|NOSPLIT, $0
// // TEXT foo(SB), $0
// s := p.From.Sym.Attribute.TextAttrString()
// if s != "" {
// fmt.Fprintf(&buf, "%s%s", sep, s)
// sep = ", "
// }
// }
//
p.Printf("TEXT %s%s(SB)", dot, f.Name)
if f.Attributes != 0 {
p.Printf(", %s", f.Attributes.Asm())
}
p.Printf(", %s\n", textsize(f))
p.clear = true
for _, node := range f.Nodes {
switch n := node.(type) {
case *ir.Instruction:
p.instruction(n)
if n.IsTerminal || n.IsUnconditionalBranch() {
p.flush()
}
case ir.Label:
p.flush()
p.ensureclear()
p.Printf("%s:\n", n)
case *ir.Comment:
p.flush()
p.ensureclear()
for _, line := range n.Lines {
p.Printf("\t// %s\n", line)
}
default:
panic("unexpected node type")
}
}
p.flush()
}
func (p *goasm) instruction(i *ir.Instruction) {
p.instructions = append(p.instructions, i)
p.clear = false
}
func (p *goasm) flush() {
if len(p.instructions) == 0 {
return
}
// Determine instruction width. Instructions with no operands are not
// considered in this calculation.
width := 0
for _, i := range p.instructions {
opcode := i.OpcodeWithSuffixes()
if len(i.Operands) > 0 && len(opcode) > width {
width = len(opcode)
}
}
// Output instruction block.
for _, i := range p.instructions {
if len(i.Operands) > 0 {
p.Printf("\t%-*s%s\n", width+1, i.OpcodeWithSuffixes(), joinOperands(i.Operands))
} else {
p.Printf("\t%s\n", i.OpcodeWithSuffixes())
}
}
p.instructions = nil
}
func (p *goasm) ensureclear() {
if !p.clear {
p.NL()
p.clear = true
}
}
func (p *goasm) global(g *ir.Global) {
p.NL()
for _, d := range g.Data {
a := operand.NewDataAddr(g.Symbol, d.Offset)
p.Printf("DATA %s/%d, %s\n", a.Asm(), d.Value.Bytes(), d.Value.Asm())
}
p.Printf("GLOBL %s(SB), %s, $%d\n", g.Symbol, g.Attributes.Asm(), g.Size)
}
func textsize(f *ir.Function) string {
// Reference: https://github.com/golang/go/blob/b115207baf6c2decc3820ada4574ef4e5ad940ec/src/cmd/internal/obj/util.go#L260-L265
//
// case TYPE_TEXTSIZE:
// if a.Val.(int32) == objabi.ArgsSizeUnknown {
// str = fmt.Sprintf("$%d", a.Offset)
// } else {
// str = fmt.Sprintf("$%d-%d", a.Offset, a.Val.(int32))
// }
//
s := "$" + strconv.Itoa(f.FrameBytes())
if argsize := f.ArgumentBytes(); argsize > 0 {
return s + "-" + strconv.Itoa(argsize)
}
return s
}
func joinOperands(operands []operand.Op) string {
asm := make([]string, len(operands))
for i, op := range operands {
asm[i] = op.Asm()
}
return strings.Join(asm, ", ")
}
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