#ifndef SIMDJSON_ARM64_BITMASK_H

#define SIMDJSON_ARM64_BITMASK_H

#include "simdjson.h"

#include "arm64/intrinsics.h"

namespace simdjson {

namespace arm64 {

//

// Perform a "cumulative bitwise xor," flipping bits each time a 1 is encountered.

//

// For example, prefix_xor(00100100) == 00011100

//

really_inline uint64_t prefix_xor(uint64_t bitmask) {

/////////////

// We could do this with PMULL, but it is apparently slow.

//

//#ifdef __ARM_FEATURE_CRYPTO // some ARM processors lack this extension

//return vmull_p64(-1ULL, bitmask);

//#else

// Analysis by @sebpop:

// When diffing the assembly for src/stage1_find_marks.cpp I see that the eors are all spread out

// in between other vector code, so effectively the extra cycles of the sequence do not matter

// because the GPR units are idle otherwise and the critical path is on the FP side.

// Also the PMULL requires two extra fmovs: GPR->FP (3 cycles in N1, 5 cycles in A72 )

// and FP->GPR (2 cycles on N1 and 5 cycles on A72.)

///////////

bitmask ^= bitmask << 1;

bitmask ^= bitmask << 2;

bitmask ^= bitmask << 4;

bitmask ^= bitmask << 8;

bitmask ^= bitmask << 16;

bitmask ^= bitmask << 32;

return bitmask;

}

} // namespace arm64

} // namespace simdjson

UNTARGET_REGION

#endif