util/bufferiszero: Split out host include files

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>

1 files changed, 76 insertions, 0 deletions

diff --git a/host/include/aarch64/host/bufferiszero.c.inc b/host/include/aarch64/host/bufferiszero.c.inc
new file mode 100644
index 0000000000..947ee7ca1f
--- /dev/null
+++ b/host/include/aarch64/host/bufferiszero.c.inc
@@ -0,0 +1,76 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * buffer_is_zero acceleration, aarch64 version.
+ */
+
+#ifdef __ARM_NEON
+#include <arm_neon.h>
+
+/*
+ * Helper for preventing the compiler from reassociating
+ * chains of binary vector operations.
+ */
+#define REASSOC_BARRIER(vec0, vec1) asm("" : "+w"(vec0), "+w"(vec1))
+
+static bool buffer_is_zero_simd(const void *buf, size_t len)
+{
+    uint32x4_t t0, t1, t2, t3;
+
+    /* Align head/tail to 16-byte boundaries.  */
+    const uint32x4_t *p = QEMU_ALIGN_PTR_DOWN(buf + 16, 16);
+    const uint32x4_t *e = QEMU_ALIGN_PTR_DOWN(buf + len - 1, 16);
+
+    /* Unaligned loads at head/tail.  */
+    t0 = vld1q_u32(buf) | vld1q_u32(buf + len - 16);
+
+    /* Collect a partial block at tail end.  */
+    t1 = e[-7] | e[-6];
+    t2 = e[-5] | e[-4];
+    t3 = e[-3] | e[-2];
+    t0 |= e[-1];
+    REASSOC_BARRIER(t0, t1);
+    REASSOC_BARRIER(t2, t3);
+    t0 |= t1;
+    t2 |= t3;
+    REASSOC_BARRIER(t0, t2);
+    t0 |= t2;
+
+    /*
+     * Loop over complete 128-byte blocks.
+     * With the head and tail removed, e - p >= 14, so the loop
+     * must iterate at least once.
+     */
+    do {
+        /*
+         * Reduce via UMAXV.  Whatever the actual result,
+         * it will only be zero if all input bytes are zero.
+         */
+        if (unlikely(vmaxvq_u32(t0) != 0)) {
+            return false;
+        }
+
+        t0 = p[0] | p[1];
+        t1 = p[2] | p[3];
+        t2 = p[4] | p[5];
+        t3 = p[6] | p[7];
+        REASSOC_BARRIER(t0, t1);
+        REASSOC_BARRIER(t2, t3);
+        t0 |= t1;
+        t2 |= t3;
+        REASSOC_BARRIER(t0, t2);
+        t0 |= t2;
+        p += 8;
+    } while (p < e - 7);
+
+    return vmaxvq_u32(t0) == 0;
+}
+
+static biz_accel_fn const accel_table[] = {
+    buffer_is_zero_int_ge256,
+    buffer_is_zero_simd,
+};
+
+#define best_accel() 1
+#else
+# include "host/include/generic/host/bufferiszero.c.inc"
+#endif