github.com/mattn/go@v0.0.0-20171011075504-07f7db3ea99f/src/crypto/sha1/sha1block_amd64.go (about)

     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  package sha1
     6  
     7  import "internal/cpu"
     8  
     9  //go:noescape
    10  func blockAVX2(dig *digest, p []byte)
    11  
    12  //go:noescape
    13  func blockAMD64(dig *digest, p []byte)
    14  
    15  var useAVX2 = cpu.X86.HasAVX2 && cpu.X86.HasBMI1 && cpu.X86.HasBMI2
    16  
    17  func block(dig *digest, p []byte) {
    18  	if useAVX2 && len(p) >= 256 {
    19  		// blockAVX2 calculates sha1 for 2 block per iteration
    20  		// it also interleaves precalculation for next block.
    21  		// So it may read up-to 192 bytes past end of p
    22  		// We may add checks inside blockAVX2, but this will
    23  		// just turn it into a copy of blockAMD64,
    24  		// so call it directly, instead.
    25  		safeLen := len(p) - 128
    26  		if safeLen%128 != 0 {
    27  			safeLen -= 64
    28  		}
    29  		blockAVX2(dig, p[:safeLen])
    30  		blockAMD64(dig, p[safeLen:])
    31  	} else {
    32  		blockAMD64(dig, p)
    33  	}
    34  }