From 9c40621584622078dcf47bb9add9a05925105130 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Philippe=20Mathieu-Daud=C3=A9?= Date: Wed, 23 Aug 2023 16:55:38 +0200 Subject: [PATCH] tcg/tcg-op: Document bswap32_i64() byte pattern MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Signed-off-by: Philippe Mathieu-Daudé Message-Id: <20230823145542.79633-5-philmd@linaro.org> Signed-off-by: Richard Henderson --- tcg/tcg-op.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c index ed0ab218a1..b56ae748b8 100644 --- a/tcg/tcg-op.c +++ b/tcg/tcg-op.c @@ -1822,6 +1822,14 @@ void tcg_gen_bswap16_i64(TCGv_i64 ret, TCGv_i64 arg, int flags) } } +/* + * bswap32_i64: 32-bit byte swap on the low bits of a 64-bit value. + * + * Byte pattern: xxxxabcd -> yyyydcba + * + * With TCG_BSWAP_IZ, x == zero, else undefined. + * With TCG_BSWAP_OZ, y == zero, with TCG_BSWAP_OS y == sign, else undefined. + */ void tcg_gen_bswap32_i64(TCGv_i64 ret, TCGv_i64 arg, int flags) { /* Only one extension flag may be present. */ @@ -1855,7 +1863,8 @@ void tcg_gen_bswap32_i64(TCGv_i64 ret, TCGv_i64 arg, int flags) } else { tcg_gen_shri_i64(t1, t1, 32); /* t1 = ....dc.. */ } - tcg_gen_or_i64(ret, t0, t1); /* ret = ssssdcba */ + tcg_gen_or_i64(ret, t0, t1); /* ret = ssssdcba (OS) */ + /* ....dcba (else) */ tcg_temp_free_i64(t0); tcg_temp_free_i64(t1); -- 2.30.2