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[124.149.254.207]) by smtp.gmail.com with ESMTPSA id o13-20020a170902778d00b001d403f12739sm19033419pll.263.2023.12.31.17.43.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 31 Dec 2023 17:43:32 -0800 (PST) Message-ID: <8fc61441-a87a-4c78-85ff-d00b7889fc8b@linaro.org> Date: Mon, 1 Jan 2024 12:43:27 +1100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] tcg/i386: use 8-bit OR or XOR for unsigned 8-bit immediates Content-Language: en-US To: Paolo Bonzini , qemu-devel@nongnu.org References: <20231228120524.70239-1-pbonzini@redhat.com> From: Richard Henderson In-Reply-To: <20231228120524.70239-1-pbonzini@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::1035; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x1035.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, T_SCC_BODY_TEXT_LINE=-0.01 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 12/28/23 23:05, Paolo Bonzini wrote: > In the case where OR or XOR has an 8-bit immediate between 128 and 255, we can > operate on a low-byte register and shorten the output by two or three bytes > (two if a prefix byte is needed for REX.B). > > Signed-off-by: Paolo Bonzini > --- > tcg/i386/tcg-target.c.inc | 7 +++++++ > 1 file changed, 7 insertions(+) Queued. I adjusted the function a bit to use a switch. r~ > > diff --git a/tcg/i386/tcg-target.c.inc b/tcg/i386/tcg-target.c.inc > index 1791b959738..a24a23f43b1 100644 > --- a/tcg/i386/tcg-target.c.inc > +++ b/tcg/i386/tcg-target.c.inc > @@ -244,6 +244,7 @@ static bool tcg_target_const_match(int64_t val, TCGType type, int ct, int vece) > #define P_VEXL 0x80000 /* Set VEX.L = 1 */ > #define P_EVEX 0x100000 /* Requires EVEX encoding */ > > +#define OPC_ARITH_EbIb (0x80) > #define OPC_ARITH_EvIz (0x81) > #define OPC_ARITH_EvIb (0x83) > #define OPC_ARITH_GvEv (0x03) /* ... plus (ARITH_FOO << 3) */ > @@ -1366,6 +1367,12 @@ static void tgen_arithi(TCGContext *s, int c, int r0, > tcg_out8(s, val); > return; > } > + if (val == (uint8_t)val && (c == ARITH_OR || c == ARITH_XOR) && > + (r0 < 4 || TCG_TARGET_REG_BITS == 64)) { > + tcg_out_modrm(s, OPC_ARITH_EbIb + P_REXB_RM, c, r0); > + tcg_out8(s, val); > + return; > + } > if (rexw == 0 || val == (int32_t)val) { > tcg_out_modrm(s, OPC_ARITH_EvIz + rexw, c, r0); > tcg_out32(s, val);