github.com/goproxy0/go@v0.0.0-20171111080102-49cc0c489d2c/src/cmd/internal/obj/x86/ytab.go (about)

     1  // Copyright 2017 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 x86
     6  
     7  type argList [6]uint8
     8  
     9  type ytab struct {
    10  	zcase   uint8
    11  	zoffset uint8
    12  
    13  	// Last arg is usually destination.
    14  	// For unary instructions unaryDst is used to determine
    15  	// if single argument is a source or destination.
    16  	args argList
    17  }
    18  
    19  // Returns true if yt is compatible with args.
    20  //
    21  // Elements from args and yt.args are used to
    22  // to index ycover table like `ycover[args[i]+yt.args[i]]`.
    23  // This means that args should contain values that already
    24  // multiplied by Ymax.
    25  func (yt *ytab) match(args []int) bool {
    26  	// Trailing Yxxx check is required to avoid a case
    27  	// where shorter arg list is matched.
    28  	// If we had exact yt.args length, it could be `yt.argc != len(args)`.
    29  	if len(args) < len(yt.args) && yt.args[len(args)] != Yxxx {
    30  		return false
    31  	}
    32  
    33  	for i := range args {
    34  		if ycover[args[i]+int(yt.args[i])] == 0 {
    35  			return false
    36  		}
    37  	}
    38  
    39  	return true
    40  }