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// Copyright 2016 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.
// This test makes sure that we don't split a single
// load up into two separate loads.
package main
import "testing"
//go:noinline
func read1(b []byte) (uint16, uint16) {
// There is only a single read of b[0]. The two
// returned values must have the same low byte.
v := b[0]
return uint16(v), uint16(v) | uint16(b[1])<<8
}
func main1(t *testing.T) {
const N = 100000
done := make(chan bool, 2)
b := make([]byte, 2)
go func() {
for i := 0; i < N; i++ {
b[0] = byte(i)
b[1] = byte(i)
}
done <- true
}()
go func() {
for i := 0; i < N; i++ {
x, y := read1(b)
if byte(x) != byte(y) {
t.Errorf("x=%x y=%x\n", x, y)
done <- false
return
}
}
done <- true
}()
<-done
<-done
}
//go:noinline
func read2(b []byte) (uint16, uint16) {
// There is only a single read of b[1]. The two
// returned values must have the same high byte.
v := uint16(b[1]) << 8
return v, uint16(b[0]) | v
}
func main2(t *testing.T) {
const N = 100000
done := make(chan bool, 2)
b := make([]byte, 2)
go func() {
for i := 0; i < N; i++ {
b[0] = byte(i)
b[1] = byte(i)
}
done <- true
}()
go func() {
for i := 0; i < N; i++ {
x, y := read2(b)
if x&0xff00 != y&0xff00 {
t.Errorf("x=%x y=%x\n", x, y)
done <- false
return
}
}
done <- true
}()
<-done
<-done
}
func TestDupLoad(t *testing.T) {
main1(t)
main2(t)
}
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