2d32a5d2a0
Split out host/bufferiszero.h.inc for x86, aarch64 and generic in order to avoid an overlong ifdef ladder. Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
77 lines
1.8 KiB
C++
77 lines
1.8 KiB
C++
/*
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* SPDX-License-Identifier: GPL-2.0-or-later
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* buffer_is_zero acceleration, aarch64 version.
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*/
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#ifdef __ARM_NEON
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#include <arm_neon.h>
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/*
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* Helper for preventing the compiler from reassociating
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* chains of binary vector operations.
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*/
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#define REASSOC_BARRIER(vec0, vec1) asm("" : "+w"(vec0), "+w"(vec1))
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static bool buffer_is_zero_simd(const void *buf, size_t len)
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{
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uint32x4_t t0, t1, t2, t3;
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/* Align head/tail to 16-byte boundaries. */
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const uint32x4_t *p = QEMU_ALIGN_PTR_DOWN(buf + 16, 16);
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const uint32x4_t *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 16);
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/* Unaligned loads at head/tail. */
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t0 = vld1q_u32(buf) | vld1q_u32(buf + len - 16);
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/* Collect a partial block at tail end. */
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t1 = e[-7] | e[-6];
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t2 = e[-5] | e[-4];
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t3 = e[-3] | e[-2];
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t0 |= e[-1];
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REASSOC_BARRIER(t0, t1);
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REASSOC_BARRIER(t2, t3);
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t0 |= t1;
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t2 |= t3;
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REASSOC_BARRIER(t0, t2);
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t0 |= t2;
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/*
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* Loop over complete 128-byte blocks.
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* With the head and tail removed, e - p >= 14, so the loop
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* must iterate at least once.
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*/
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do {
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/*
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* Reduce via UMAXV. Whatever the actual result,
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* it will only be zero if all input bytes are zero.
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*/
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if (unlikely(vmaxvq_u32(t0) != 0)) {
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return false;
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}
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t0 = p[0] | p[1];
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t1 = p[2] | p[3];
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t2 = p[4] | p[5];
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t3 = p[6] | p[7];
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REASSOC_BARRIER(t0, t1);
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REASSOC_BARRIER(t2, t3);
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t0 |= t1;
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t2 |= t3;
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REASSOC_BARRIER(t0, t2);
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t0 |= t2;
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p += 8;
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} while (p < e - 7);
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return vmaxvq_u32(t0) == 0;
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}
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static biz_accel_fn const accel_table[] = {
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buffer_is_zero_int_ge256,
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buffer_is_zero_simd,
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};
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#define best_accel() 1
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#else
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# include "host/include/generic/host/bufferiszero.c.inc"
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#endif
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