decode_amd64.s [356:404]:
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slowForwardCopy:
	// !!! If the forward copy is longer than 16 bytes, or if offset < 8, we
	// can still try 8-byte load stores, provided we can overrun up to 10 extra
	// bytes. As above, the overrun will be fixed up by subsequent iterations
	// of the outermost loop.
	//
	// The C++ snappy code calls this technique IncrementalCopyFastPath. Its
	// commentary says:
	//
	// ----
	//
	// The main part of this loop is a simple copy of eight bytes at a time
	// until we've copied (at least) the requested amount of bytes.  However,
	// if d and d-offset are less than eight bytes apart (indicating a
	// repeating pattern of length < 8), we first need to expand the pattern in
	// order to get the correct results. For instance, if the buffer looks like
	// this, with the eight-byte <d-offset> and <d> patterns marked as
	// intervals:
	//
	//    abxxxxxxxxxxxx
	//    [------]           d-offset
	//      [------]         d
	//
	// a single eight-byte copy from <d-offset> to <d> will repeat the pattern
	// once, after which we can move <d> two bytes without moving <d-offset>:
	//
	//    ababxxxxxxxxxx
	//    [------]           d-offset
	//        [------]       d
	//
	// and repeat the exercise until the two no longer overlap.
	//
	// This allows us to do very well in the special case of one single byte
	// repeated many times, without taking a big hit for more general cases.
	//
	// The worst case of extra writing past the end of the match occurs when
	// offset == 1 and length == 1; the last copy will read from byte positions
	// [0..7] and write to [4..11], whereas it was only supposed to write to
	// position 1. Thus, ten excess bytes.
	//
	// ----
	//
	// That "10 byte overrun" worst case is confirmed by Go's
	// TestSlowForwardCopyOverrun, which also tests the fixUpSlowForwardCopy
	// and finishSlowForwardCopy algorithm.
	//
	// if length > len(dst)-d-10 {
	//   goto verySlowForwardCopy
	// }
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decode_arm64.s [358:406]:
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slowForwardCopy:
	// !!! If the forward copy is longer than 16 bytes, or if offset < 8, we
	// can still try 8-byte load stores, provided we can overrun up to 10 extra
	// bytes. As above, the overrun will be fixed up by subsequent iterations
	// of the outermost loop.
	//
	// The C++ snappy code calls this technique IncrementalCopyFastPath. Its
	// commentary says:
	//
	// ----
	//
	// The main part of this loop is a simple copy of eight bytes at a time
	// until we've copied (at least) the requested amount of bytes.  However,
	// if d and d-offset are less than eight bytes apart (indicating a
	// repeating pattern of length < 8), we first need to expand the pattern in
	// order to get the correct results. For instance, if the buffer looks like
	// this, with the eight-byte <d-offset> and <d> patterns marked as
	// intervals:
	//
	//    abxxxxxxxxxxxx
	//    [------]           d-offset
	//      [------]         d
	//
	// a single eight-byte copy from <d-offset> to <d> will repeat the pattern
	// once, after which we can move <d> two bytes without moving <d-offset>:
	//
	//    ababxxxxxxxxxx
	//    [------]           d-offset
	//        [------]       d
	//
	// and repeat the exercise until the two no longer overlap.
	//
	// This allows us to do very well in the special case of one single byte
	// repeated many times, without taking a big hit for more general cases.
	//
	// The worst case of extra writing past the end of the match occurs when
	// offset == 1 and length == 1; the last copy will read from byte positions
	// [0..7] and write to [4..11], whereas it was only supposed to write to
	// position 1. Thus, ten excess bytes.
	//
	// ----
	//
	// That "10 byte overrun" worst case is confirmed by Go's
	// TestSlowForwardCopyOverrun, which also tests the fixUpSlowForwardCopy
	// and finishSlowForwardCopy algorithm.
	//
	// if length > len(dst)-d-10 {
	//   goto verySlowForwardCopy
	// }
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