golang ytab 代码
文件路径：/src/cmd/internal/obj/x86/ytab.go
/ Copyright 2017 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 x86
/ argListMax specifies upper arg count limit expected to be carried by obj.Prog.
/ Max len(obj.Prog.RestArgs) can be inferred from this to be 4.
const argListMax int = 6
type argList [argListMax]uint8
type ytab struct {
zcase uint8
zoffset uint8
/ Last arg is usually destination.
/ For unary instructions unaryDst is used to determine
/ if single argument is a source or destination.
args argList
}
/ Returns true if yt is compatible with args.
/
/ Elements from args and yt.args are used
/ to index ycover table like `ycover[args[i]+yt.args[i]]`.
/ This means that args should contain values that already
/ multiplied by Ymax.
func (yt *ytab) match(args []int) bool {
/ Trailing Yxxx check is required to avoid a case
/ where shorter arg list is matched.
/ If we had exact yt.args length, it could be `yt.argc != len(args)`.
if len(args) < len(yt.args) && yt.args[len(args)] != Yxxx {
return false
}
for i := range args {
if ycover[args[i]+int(yt.args[i])] == 0 {
return false
}
}
return true
}