xchg8_test.go

     1  // Copyright 2024 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 atomic_test
     6  
     7  import (
     8  	"internal/runtime/atomic"
     9  	"testing"
    10  )
    11  
    12  func TestXchg8(t *testing.T) {
    13  	var a [16]uint8
    14  	for i := range a {
    15  		next := uint8(i + 50)
    16  		a[i] = next
    17  	}
    18  	b := a
    19  
    20  	// Compare behavior against non-atomic implementation. Expect the operation
    21  	// to work at any byte offset and to not clobber neighboring values.
    22  	for i := range a {
    23  		next := uint8(i + 100)
    24  		pa := atomic.Xchg8(&a[i], next)
    25  		pb := b[i]
    26  		b[i] = next
    27  		if pa != pb {
    28  			t.Errorf("atomic.Xchg8(a[%d]); %d != %d", i, pa, pb)
    29  		}
    30  		if a != b {
    31  			t.Errorf("after atomic.Xchg8(a[%d]); %d != %d", i, a, b)
    32  		}
    33  		if t.Failed() {
    34  			break
    35  		}
    36  	}
    37  }
    38  
    39  func BenchmarkXchg8(b *testing.B) {
    40  	var x [512]uint8 // give byte its own cache line
    41  	sink = &x
    42  	for i := 0; i < b.N; i++ {
    43  		atomic.Xchg8(&x[255], uint8(i))
    44  	}
    45  }
    46  
    47  func BenchmarkXchg8Parallel(b *testing.B) {
    48  	var x [512]uint8 // give byte its own cache line
    49  	sink = &x
    50  	b.RunParallel(func(pb *testing.PB) {
    51  		i := uint8(0)
    52  		for pb.Next() {
    53  			atomic.Xchg8(&x[255], i)
    54  			i++
    55  		}
    56  	})
    57  }
    58
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