dupLoad_test.go

     1  // Copyright 2016 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  // This test makes sure that we don't split a single
     6  // load up into two separate loads.
     7  
     8  package main
     9  
    10  import "testing"
    11  
    12  //go:noinline
    13  func read1(b []byte) (uint16, uint16) {
    14  	// There is only a single read of b[0].  The two
    15  	// returned values must have the same low byte.
    16  	v := b[0]
    17  	return uint16(v), uint16(v) | uint16(b[1])<<8
    18  }
    19  
    20  func main1(t *testing.T) {
    21  	const N = 100000
    22  	done := make(chan bool, 2)
    23  	b := make([]byte, 2)
    24  	go func() {
    25  		for i := 0; i < N; i++ {
    26  			b[0] = byte(i)
    27  			b[1] = byte(i)
    28  		}
    29  		done <- true
    30  	}()
    31  	go func() {
    32  		for i := 0; i < N; i++ {
    33  			x, y := read1(b)
    34  			if byte(x) != byte(y) {
    35  				t.Errorf("x=%x y=%x\n", x, y)
    36  				done <- false
    37  				return
    38  			}
    39  		}
    40  		done <- true
    41  	}()
    42  	<-done
    43  	<-done
    44  }
    45  
    46  //go:noinline
    47  func read2(b []byte) (uint16, uint16) {
    48  	// There is only a single read of b[1].  The two
    49  	// returned values must have the same high byte.
    50  	v := uint16(b[1]) << 8
    51  	return v, uint16(b[0]) | v
    52  }
    53  
    54  func main2(t *testing.T) {
    55  	const N = 100000
    56  	done := make(chan bool, 2)
    57  	b := make([]byte, 2)
    58  	go func() {
    59  		for i := 0; i < N; i++ {
    60  			b[0] = byte(i)
    61  			b[1] = byte(i)
    62  		}
    63  		done <- true
    64  	}()
    65  	go func() {
    66  		for i := 0; i < N; i++ {
    67  			x, y := read2(b)
    68  			if x&0xff00 != y&0xff00 {
    69  				t.Errorf("x=%x y=%x\n", x, y)
    70  				done <- false
    71  				return
    72  			}
    73  		}
    74  		done <- true
    75  	}()
    76  	<-done
    77  	<-done
    78  }
    79  
    80  func TestDupLoad(t *testing.T) {
    81  	main1(t)
    82  	main2(t)
    83  }
    84
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