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[37.158.143.169]) by smtp.gmail.com with ESMTPSA id w15sm20760056wrk.77.2021.11.09.09.22.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Nov 2021 09:22:04 -0800 (PST) Subject: Re: [PULL v2 28/60] tcg/optimize: Split out fold_extract2 To: Peter Maydell References: <20211029043329.1518029-1-richard.henderson@linaro.org> <20211029043329.1518029-29-richard.henderson@linaro.org> From: Richard Henderson Message-ID: <1a06b8c8-f10e-3de7-5a43-fffffce2dd76@linaro.org> Date: Tue, 9 Nov 2021 18:22:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::435 (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::435; envelope-from=richard.henderson@linaro.org; helo=mail-wr1-x435.google.com X-Spam_score_int: -46 X-Spam_score: -4.7 X-Spam_bar: ---- X-Spam_report: (-4.7 / 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, NICE_REPLY_A=-3.364, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, 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: , Cc: Luis Pires , qemu-devel@nongnu.org, =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 11/9/21 5:52 PM, Peter Maydell wrote: > On Fri, 29 Oct 2021 at 05:59, Richard Henderson > wrote: >> >> Reviewed-by: Luis Pires >> Reviewed-by: Philippe Mathieu-Daudé >> Signed-off-by: Richard Henderson >> --- >> tcg/optimize.c | 39 ++++++++++++++++++++++----------------- >> 1 file changed, 22 insertions(+), 17 deletions(-) >> >> diff --git a/tcg/optimize.c b/tcg/optimize.c >> index 110b3d1cc2..faedbdbfb8 100644 >> --- a/tcg/optimize.c >> +++ b/tcg/optimize.c >> @@ -888,6 +888,25 @@ static bool fold_eqv(OptContext *ctx, TCGOp *op) >> return fold_const2(ctx, op); >> } > > Hi; Coverity warns about a shift in here (CID 1465220): > >> >> +static bool fold_extract2(OptContext *ctx, TCGOp *op) >> +{ >> + if (arg_is_const(op->args[1]) && arg_is_const(op->args[2])) { >> + uint64_t v1 = arg_info(op->args[1])->val; >> + uint64_t v2 = arg_info(op->args[2])->val; >> + int shr = op->args[3]; >> + >> + if (op->opc == INDEX_op_extract2_i64) { >> + v1 >>= shr; >> + v2 <<= 64 - shr; >> + } else { >> + v1 = (uint32_t)v1 >> shr; >> + v2 = (int32_t)v2 << (32 - shr); > > Here we do the shift at 32-bits and then assign it into a 64-bit > variable, which triggers Coverity's usual OVERFLOW_BEFORE_WIDEN > heuristic. Is the 32-bitness intentional? Yep. I'll add another cast. r~