cheat.go

     1  // Copyright 2025 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  //go:build ignore
     6  
     7  // This program can be compiled with -S to produce a “cheat sheet”
     8  // for filling out a new Arch: the compiler will show you how to implement
     9  // the various operations.
    10  //
    11  // Usage (replace TARGET with your target architecture):
    12  //
    13  //	GOOS=linux GOARCH=TARGET go build -gcflags='-p=cheat -S' cheat.go
    14  
    15  package p
    16  
    17  import "math/bits"
    18  
    19  func mov(x, y uint) uint             { return y }
    20  func zero() uint                     { return 0 }
    21  func add(x, y uint) uint             { return x + y }
    22  func adds(x, y, c uint) (uint, uint) { return bits.Add(x, y, 0) }
    23  func adcs(x, y, c uint) (uint, uint) { return bits.Add(x, y, c) }
    24  func sub(x, y uint) uint             { return x + y }
    25  func subs(x, y uint) (uint, uint)    { return bits.Sub(x, y, 0) }
    26  func sbcs(x, y, c uint) (uint, uint) { return bits.Sub(x, y, c) }
    27  func mul(x, y uint) uint             { return x * y }
    28  func mulWide(x, y uint) (uint, uint) { return bits.Mul(x, y) }
    29  func lsh(x, s uint) uint             { return x << s }
    30  func rsh(x, s uint) uint             { return x >> s }
    31  func and(x, y uint) uint             { return x & y }
    32  func or(x, y uint) uint              { return x | y }
    33  func xor(x, y uint) uint             { return x ^ y }
    34  func neg(x uint) uint                { return -x }
    35  func loop(x int) int {
    36  	s := 0
    37  	for i := 1; i < x; i++ {
    38  		s += i
    39  		if s == 98 { // useful for jmpEqual
    40  			return 99
    41  		}
    42  		if s == 99 {
    43  			return 100
    44  		}
    45  		if s == 0 { // useful for jmpZero
    46  			return 101
    47  		}
    48  		if s != 0 { // useful for jmpNonZero
    49  			s *= 3
    50  		}
    51  		s += 2 // keep last condition from being inverted
    52  	}
    53  	return s
    54  }
    55  func mem(x *[10]struct{ a, b uint }, i int) uint { return x[i].b }
    56
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