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([2602:47:d483:7301:72f0:1ea7:85d2:141e]) by smtp.gmail.com with ESMTPSA id j25-20020aa783d9000000b006873aa079aasm10117871pfn.171.2023.08.23.13.27.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Aug 2023 13:27:04 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Subject: [PULL 40/48] tcg/tcg-op: Document bswap16_i64() byte pattern Date: Wed, 23 Aug 2023 13:23:18 -0700 Message-Id: <20230823202326.1353645-41-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230823202326.1353645-1-richard.henderson@linaro.org> References: <20230823202326.1353645-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::432; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x432.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Philippe Mathieu-Daudé Signed-off-by: Philippe Mathieu-Daudé Message-Id: <20230823145542.79633-3-philmd@linaro.org> Signed-off-by: Richard Henderson --- tcg/tcg-op.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c index fc3a0ab7fc..88c7c60ffe 100644 --- a/tcg/tcg-op.c +++ b/tcg/tcg-op.c @@ -1767,6 +1767,14 @@ void tcg_gen_ext32u_i64(TCGv_i64 ret, TCGv_i64 arg) } } +/* + * bswap16_i64: 16-bit byte swap on the low bits of a 64-bit value. + * + * Byte pattern: xxxxxxxxab -> yyyyyyyyba + * + * 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_bswap16_i64(TCGv_i64 ret, TCGv_i64 arg, int flags) { /* Only one extension flag may be present. */ @@ -1785,22 +1793,25 @@ void tcg_gen_bswap16_i64(TCGv_i64 ret, TCGv_i64 arg, int flags) TCGv_i64 t0 = tcg_temp_ebb_new_i64(); TCGv_i64 t1 = tcg_temp_ebb_new_i64(); - tcg_gen_shri_i64(t0, arg, 8); + /* arg = ......ab or xxxxxxab */ + tcg_gen_shri_i64(t0, arg, 8); /* t0 = .......a or .xxxxxxa */ if (!(flags & TCG_BSWAP_IZ)) { - tcg_gen_ext8u_i64(t0, t0); + tcg_gen_ext8u_i64(t0, t0); /* t0 = .......a */ } if (flags & TCG_BSWAP_OS) { - tcg_gen_shli_i64(t1, arg, 56); - tcg_gen_sari_i64(t1, t1, 48); + tcg_gen_shli_i64(t1, arg, 56); /* t1 = b....... */ + tcg_gen_sari_i64(t1, t1, 48); /* t1 = ssssssb. */ } else if (flags & TCG_BSWAP_OZ) { - tcg_gen_ext8u_i64(t1, arg); - tcg_gen_shli_i64(t1, t1, 8); + tcg_gen_ext8u_i64(t1, arg); /* t1 = .......b */ + tcg_gen_shli_i64(t1, t1, 8); /* t1 = ......b. */ } else { - tcg_gen_shli_i64(t1, arg, 8); + tcg_gen_shli_i64(t1, arg, 8); /* t1 = xxxxxab. */ } - tcg_gen_or_i64(ret, t0, t1); + tcg_gen_or_i64(ret, t0, t1); /* ret = ......ba (OZ) */ + /* ssssssba (OS) */ + /* xxxxxaba (no flag) */ tcg_temp_free_i64(t0); tcg_temp_free_i64(t1); }