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[98.210.197.24]) by smtp.gmail.com with ESMTPSA id q13-20020a9d57cd000000b006ce2f4861c5sm2295248oti.62.2023.10.25.09.25.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Oct 2023 09:25:49 -0700 (PDT) Message-ID: <04f85309-4b40-4797-a424-ff207dd0724d@rivosinc.com> Date: Wed, 25 Oct 2023 09:25:47 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] RISC-V: elide sign extend when expanding cmp_and_jump Content-Language: en-US To: Robin Dapp , gcc-patches@gcc.gnu.org Cc: gnu-toolchain@rivosinc.com, Jeff Law References: <20231025050155.627837-1-vineetg@rivosinc.com> <7fe582bc-d259-4d2a-bedf-4e1a334d7fc3@gmail.com> From: Vineet Gupta In-Reply-To: <7fe582bc-d259-4d2a-bedf-4e1a334d7fc3@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3.6 required=5.0 tests=BAYES_00,BODY_8BITS,DKIM_SIGNED,DKIM_VALID,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hey Robin, On 10/25/23 00:12, Robin Dapp wrote: > Hi Vineet, > > I was thinking of two things while skimming the code: > > - Couldn't we do this in the expanders directly? Or is the > subreg-promoted info gone until we reach that? Following is the call stack involved:   expand_gimple_cond     do_compare_and_jump        emit_cmp_and_jump_insns            gen_cbranchqi4                riscv_expand_conditional_branch                    riscv_emit_int_compare                       riscv_extend_comparands Last function is what introduces the extraneous sign extends, w/o taking subreg-promoted into consideration and what my patch attempts to address. > - Should some common-code part be more suited to handle that? > We already elide redundant sign-zero extensions for other > reasons. Maybe we could add subreg promoted handling there? Not in the context of this specific issue. -Vineet