[FFmpeg-devel] [PATCH] riscv: add av_bswap{16,32,64} with Zbb

[remi@remlab.net]

From: Rémi Denis-Courmont <remi@remlab.net>

If the target supports the Basic bit-manipulation (Zbb) extension, then
REV8 is available to reverse byte order. Note that this instruction
only exists at the "XLEN" register size (available as __riscv_xlen).
---
 libavutil/bswap.h       |  2 ++
 libavutil/riscv/bswap.h | 74 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 libavutil/riscv/bswap.h

diff --git a/libavutil/bswap.h b/libavutil/bswap.h
index 91cb79538d..4840ab433f 100644
--- a/libavutil/bswap.h
+++ b/libavutil/bswap.h
@@ -40,6 +40,8 @@
 #   include "arm/bswap.h"
 #elif ARCH_AVR32
 #   include "avr32/bswap.h"
+#elif ARCH_RISCV
+#   include "riscv/bswap.h"
 #elif ARCH_SH4
 #   include "sh4/bswap.h"
 #elif ARCH_X86
diff --git a/libavutil/riscv/bswap.h b/libavutil/riscv/bswap.h
new file mode 100644
index 0000000000..de106db5d1
--- /dev/null
+++ b/libavutil/riscv/bswap.h
@@ -0,0 +1,74 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_RISCV_BSWAP_H
+#define AVUTIL_RISCV_BSWAP_H
+
+#include <stdint.h>
+#include "config.h"
+#include "libavutil/attributes.h"
+
+#if __riscv_zbb && HAVE_INLINE_ASM
+
+static av_always_inline av_const uintptr_t av_bswap_xlen(uintptr_t x)
+{
+    uintptr_t y;
+
+    __asm__("rev8 %0, %1" : "=r" (y) : "r" (x));
+    return y;
+}
+
+#define av_bswap16 av_bswap16
+
+static av_always_inline av_const uint_fast16_t av_bswap16(uint_fast16_t x)
+{
+    return av_bswap_xlen(x) >> (__riscv_xlen - 16);
+}
+
+#if (__riscv_xlen == 32)
+#define av_bswap32 av_bswap_xlen
+#define av_bswap64 av_bswap64
+
+static av_always_inline av_const uint64_t av_bswap64(uint64_t x)
+{
+    return (((uint64_t)av_bswap32(x)) << 32) | av_bswap32(x >> 32);
+}
+
+#else
+#define av_bswap32 av_bswap32
+
+static av_always_inline av_const uint_fast32_t av_bswap32(uint_fast32_t x)
+{
+    return av_bswap_xlen(x) >> (__riscv_xlen - 32);
+}
+
+#if (__riscv_xlen == 64)
+#define av_bswap64 av_bswap_xlen
+
+#else
+#define av_bswap64 av_bswap64
+
+static av_always_inline av_const uint_fast64_t av_bswap64(uint_fast64_t x)
+{
+    return av_bswap_xlen(x) >> (__riscv_xlen - 64);
+}
+
+#endif /* __riscv_xlen > 64 */
+#endif /* __riscv_xlen > 32 */
+#endif /* __riscv_zbb */
+#endif /* AVUTIL_RISCV_BSWAP_H */
-- 
2.37.2

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