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// Copyright 2015 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.
package runtime
import (
"internal/cpu"
)
var memmoveBits uint8
const (
// avxSupported indicates that the CPU supports AVX instructions.
avxSupported = 1 << 0
// repmovsPreferred indicates that REP MOVSx instruction is more
// efficient on the CPU.
repmovsPreferred = 1 << 1
)
func init() {
// Here we assume that on modern CPUs with both FSRM and ERMS features,
// copying data blocks of 2KB or larger using the REP MOVSB instruction
// will be more efficient to avoid having to keep up with CPU generations.
// Therefore, we may retain a BlockList mechanism to ensure that microarchitectures
// that do not fit this case may appear in the future.
// We enable it on Intel CPUs first, and we may support more platforms
// in the future.
isERMSNiceCPU := isIntel
useREPMOV := isERMSNiceCPU && cpu.X86.HasERMS && cpu.X86.HasFSRM
if cpu.X86.HasAVX {
memmoveBits |= avxSupported
}
if useREPMOV {
memmoveBits |= repmovsPreferred
}
}
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