accel/tcg: Extract load_atom_extract_al16_or_al8 to host header

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/host/include/generic/host/load-extract-al16-al8.h b/host/include/generic/host/load-extract-al16-al8.h
new file mode 100644
index 0000000000..d95556130f
--- /dev/null
+++ b/host/include/generic/host/load-extract-al16-al8.h
@@ -0,0 +1,45 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Atomic extract 64 from 128-bit, generic version.
+ *
+ * Copyright (C) 2023 Linaro, Ltd.
+ */
+
+#ifndef HOST_LOAD_EXTRACT_AL16_AL8_H
+#define HOST_LOAD_EXTRACT_AL16_AL8_H
+
+/**
+ * load_atom_extract_al16_or_al8:
+ * @pv: host address
+ * @s: object size in bytes, @s <= 8.
+ *
+ * Load @s bytes from @pv, when pv % s != 0.  If [p, p+s-1] does not
+ * cross an 16-byte boundary then the access must be 16-byte atomic,
+ * otherwise the access must be 8-byte atomic.
+ */
+static inline uint64_t ATTRIBUTE_ATOMIC128_OPT
+load_atom_extract_al16_or_al8(void *pv, int s)
+{
+    uintptr_t pi = (uintptr_t)pv;
+    int o = pi & 7;
+    int shr = (HOST_BIG_ENDIAN ? 16 - s - o : o) * 8;
+    Int128 r;
+
+    pv = (void *)(pi & ~7);
+    if (pi & 8) {
+        uint64_t *p8 = __builtin_assume_aligned(pv, 16, 8);
+        uint64_t a = qatomic_read__nocheck(p8);
+        uint64_t b = qatomic_read__nocheck(p8 + 1);
+
+        if (HOST_BIG_ENDIAN) {
+            r = int128_make128(b, a);
+        } else {
+            r = int128_make128(a, b);
+        }
+    } else {
+        r = atomic16_read_ro(pv);
+    }
+    return int128_getlo(int128_urshift(r, shr));
+}
+
+#endif /* HOST_LOAD_EXTRACT_AL16_AL8_H */