87 lines
2.2 KiB
Go
87 lines
2.2 KiB
Go
// Copyright 2017 The go-interpreter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package operators provides all operators used by WebAssembly bytecode,
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// together with their parameter and return type(s).
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package operators
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import (
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"fmt"
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"github.com/go-interpreter/wagon/wasm"
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)
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var (
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ops [256]Op // an array of Op values mapped by wasm opcodes, used by New().
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noReturn = wasm.ValueType(wasm.BlockTypeEmpty)
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)
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// Op describes a WASM operator.
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type Op struct {
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Code byte // The single-byte opcode
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Name string // The name of the operator
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// Whether this operator is polymorphic.
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// A polymorphic operator has a variable arity. call, call_indirect, and
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// drop are examples of polymorphic operators.
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Polymorphic bool
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Args []wasm.ValueType // an array of value types used by the operator as arguments, is nil for polymorphic operators
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Returns wasm.ValueType // the value returned (pushed) by the operator, is 0 for polymorphic operators
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}
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func (o Op) IsValid() bool {
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return o.Name != ""
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}
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func newOp(code byte, name string, args []wasm.ValueType, returns wasm.ValueType) byte {
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if ops[code].IsValid() {
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panic(fmt.Errorf("Opcode %#x is already assigned to %s", code, ops[code].Name))
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}
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op := Op{
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Code: code,
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Name: name,
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Polymorphic: false,
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Args: args,
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Returns: returns,
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}
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ops[code] = op
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return code
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}
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func newPolymorphicOp(code byte, name string) byte {
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if ops[code].IsValid() {
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panic(fmt.Errorf("Opcode %#x is already assigned to %s", code, ops[code].Name))
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}
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op := Op{
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Code: code,
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Name: name,
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Polymorphic: true,
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}
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ops[code] = op
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return code
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}
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type InvalidOpcodeError byte
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func (e InvalidOpcodeError) Error() string {
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return fmt.Sprintf("Invalid opcode: %#x", byte(e))
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}
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// New returns the Op object for a valid given opcode.
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// If code is invalid, an ErrInvalidOpcode is returned.
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func New(code byte) (Op, error) {
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var op Op
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if int(code) >= len(ops) {
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return op, InvalidOpcodeError(code)
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}
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op = ops[code]
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if !op.IsValid() {
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return op, InvalidOpcodeError(code)
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}
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return op, nil
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}
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