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([2602:47:d483:7301:72f0:1ea7:85d2:141e]) by smtp.gmail.com with ESMTPSA id iz22-20020a170902ef9600b001b9da42cd7dsm11418641plb.279.2023.08.23.13.24.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Aug 2023 13:24:03 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Subject: [PULL 39/48] tcg/tcg-op: Document bswap16_i32() byte pattern Date: Wed, 23 Aug 2023 13:23:17 -0700 Message-Id: <20230823202326.1353645-40-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::635; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x635.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: <20230823145542.79633-2-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 b59a50a5a9..fc3a0ab7fc 100644 --- a/tcg/tcg-op.c +++ b/tcg/tcg-op.c @@ -1035,6 +1035,14 @@ void tcg_gen_ext16u_i32(TCGv_i32 ret, TCGv_i32 arg) } } +/* + * bswap16_i32: 16-bit byte swap on the low bits of a 32-bit value. + * + * Byte pattern: xxab -> yyba + * + * 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_i32(TCGv_i32 ret, TCGv_i32 arg, int flags) { /* Only one extension flag may be present. */ @@ -1046,22 +1054,25 @@ void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg, int flags) TCGv_i32 t0 = tcg_temp_ebb_new_i32(); TCGv_i32 t1 = tcg_temp_ebb_new_i32(); - tcg_gen_shri_i32(t0, arg, 8); + /* arg = ..ab (IZ) xxab (!IZ) */ + tcg_gen_shri_i32(t0, arg, 8); /* t0 = ...a (IZ) .xxa (!IZ) */ if (!(flags & TCG_BSWAP_IZ)) { - tcg_gen_ext8u_i32(t0, t0); + tcg_gen_ext8u_i32(t0, t0); /* t0 = ...a */ } if (flags & TCG_BSWAP_OS) { - tcg_gen_shli_i32(t1, arg, 24); - tcg_gen_sari_i32(t1, t1, 16); + tcg_gen_shli_i32(t1, arg, 24); /* t1 = b... */ + tcg_gen_sari_i32(t1, t1, 16); /* t1 = ssb. */ } else if (flags & TCG_BSWAP_OZ) { - tcg_gen_ext8u_i32(t1, arg); - tcg_gen_shli_i32(t1, t1, 8); + tcg_gen_ext8u_i32(t1, arg); /* t1 = ...b */ + tcg_gen_shli_i32(t1, t1, 8); /* t1 = ..b. */ } else { - tcg_gen_shli_i32(t1, arg, 8); + tcg_gen_shli_i32(t1, arg, 8); /* t1 = xab. */ } - tcg_gen_or_i32(ret, t0, t1); + tcg_gen_or_i32(ret, t0, t1); /* ret = ..ba (OZ) */ + /* = ssba (OS) */ + /* = xaba (no flag) */ tcg_temp_free_i32(t0); tcg_temp_free_i32(t1); }