backends: 添加 wasm 初始骨架代码

internal/backends/compiler_wasm/compile_wasm_.go

+// 版权 @2021 凹语言 作者。保留所有权利。
+
+package compiler_wasm
+
+import (
+	"bytes"
+
+	"github.com/wa-lang/wa/internal/3rdparty/wasm/encoding"
+	"github.com/wa-lang/wa/internal/3rdparty/wasm/instruction"
+	"github.com/wa-lang/wa/internal/3rdparty/wasm/module"
+	"github.com/wa-lang/wa/internal/3rdparty/wasm/types"
+	"github.com/wa-lang/wa/internal/ast"
+	"github.com/wa-lang/wa/internal/loader"
+)
+
+type Compiler struct {
+	stages []func() error
+
+	prog *loader.Program
+
+	globalNames []string
+	globalNodes map[string]*ast.Ident
+
+	module   *module.Module
+	mainBody *module.CodeEntry
+
+	tinyMainIndex  uint32
+	tinyReadIndex  uint32
+	tinyWriteIndex uint32
+}
+
+func New() *Compiler {
+	p := new(Compiler)
+	p.stages = []func() error{
+		p.reset,
+		p.initModule,
+		p.emitGlobals,
+		p.emitMainBody,
+	}
+	return p
+}
+
+func (p *Compiler) Compile(prog *loader.Program) (output string, err error) {
+	p.prog = prog
+
+	for _, stage := range p.stages {
+		if err := stage(); err != nil {
+			return "", err
+		}
+	}
+
+	var buf bytes.Buffer
+	if err := encoding.WriteModule(&buf, p.module); err != nil {
+		return "", err
+	}
+
+	return buf.String(), nil
+}
+
+func (p *Compiler) reset() error {
+	p.globalNames = []string{}
+	p.globalNodes = make(map[string]*ast.Ident)
+	return nil
+}
+
+func (p *Compiler) initModule() error {
+	p.module = &module.Module{
+		Names: module.NameSection{
+			Module: "walang",
+		},
+		Memory: module.MemorySection{
+			Memorys: []module.Memory{
+				{InitPages: 1, MaxPages: 1},
+			},
+		},
+		Export: module.ExportSection{
+			Exports: []module.Export{
+				{
+					Name: "memory",
+					Descriptor: module.ExportDescriptor{
+						Type:  module.MemoryExportType,
+						Index: 0,
+					},
+				},
+			},
+		},
+	}
+
+	// init types
+	p.tinyReadIndex = 0
+	p.tinyWriteIndex = 1
+	p.tinyMainIndex = 2
+
+	p.module.Type.Functions = []module.FunctionType{
+		// func __tiny_read() int32
+		{Results: []types.ValueType{types.I32}},
+		// func __tiny_write(x int32)
+		{Params: []types.ValueType{types.I32}},
+		// func _start
+		{},
+	}
+
+	// import
+	p.module.Import.Imports = []module.Import{
+		{
+			Module: "env",
+			Name:   "__tiny_read",
+			Descriptor: module.FunctionImport{
+				Func: p.tinyReadIndex,
+			},
+		},
+		{
+			Module: "env",
+			Name:   "__tiny_write",
+			Descriptor: module.FunctionImport{
+				Func: p.tinyWriteIndex,
+			},
+		},
+	}
+
+	// _start func
+	p.module.Function.TypeIndices = []uint32{
+		p.tinyMainIndex,
+	}
+	p.module.Names.Functions = append(p.module.Names.Functions, module.NameMap{
+		Index: p.tinyMainIndex,
+		Name:  "_start",
+	})
+
+	// _start func body
+	{
+		var entry = &module.CodeEntry{
+			Func: module.Function{
+				Locals: []module.LocalDeclaration{},
+				Expr: module.Expr{
+					Instrs: []instruction.Instruction{
+						instruction.I32Const{Value: 42},
+						instruction.Call{Index: p.tinyWriteIndex},
+						instruction.Return{},
+					},
+				},
+			},
+		}
+
+		var buf bytes.Buffer
+		if err := encoding.WriteCodeEntry(&buf, entry); err != nil {
+			return err
+		}
+
+		p.module.Code.Segments = append(p.module.Code.Segments, module.RawCodeSegment{
+			Code: buf.Bytes(),
+		})
+	}
+
+	// export _start
+	p.module.Export.Exports = append(p.module.Export.Exports, module.Export{
+		Name: "_start",
+		Descriptor: module.ExportDescriptor{
+			Type:  module.FunctionExportType,
+			Index: p.tinyMainIndex,
+		},
+	})
+
+	return nil
+}
+
+func (p *Compiler) emitGlobals() error {
+	if len(p.module.Global.Globals) > 0 {
+		return nil
+	}
+	panic("TODO")
+}
+
+func (p *Compiler) emitMainBody() error {
+	p.mainBody = &module.CodeEntry{
+		Func: module.Function{
+			Locals: []module.LocalDeclaration{},
+			Expr: module.Expr{
+				Instrs: []instruction.Instruction{
+					// instruction.I32Const{Value: 42 + 1},
+					// instruction.Call{Index: p.tinyWriteIndex},
+				},
+			},
+		},
+	}
+
+	if err := p.compileNone(&p.mainBody.Func.Expr, nil); err != nil {
+		return err
+	}
+
+	var buf bytes.Buffer
+	if err := encoding.WriteCodeEntry(&buf, p.mainBody); err != nil {
+		return err
+	}
+
+	// replace main body
+	p.module.Code.Segments = []module.RawCodeSegment{
+		{Code: buf.Bytes()},
+	}
+
+	return nil
+}
+
+func (p *Compiler) compileNone(ctx *module.Expr, node ast.Node) error {
+	if node == nil {
+		return nil
+	}
+
+	panic("TODO")
+}
+
+func (p *Compiler) globalIndexByName(name string) uint32 {
+	for i, s := range p.globalNames {
+		if s == name {
+			return uint32(i) + 1
+		}
+	}
+	return 0
+}
+
+func (p *Compiler) emit(ctx *module.Expr, x ...instruction.Instruction) {
+	ctx.Instrs = append(ctx.Instrs, x...)
+}