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In-Reply-To: <13fe668d-7856-4881-8ff2-f7e91b3a72da@gmail.com> CC: gcc-patches@gcc.gnu.org From: Palmer Dabbelt To: jeffreyalaw@gmail.com Message-ID: Mime-Version: 1.0 (MHng) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3.9 required=5.0 tests=BAYES_00,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: On Mon, 25 Mar 2024 13:49:18 PDT (-0700), jeffreyalaw@gmail.com wrote: > > > On 3/25/24 2:31 PM, Palmer Dabbelt wrote: >> On Mon, 25 Mar 2024 13:27:34 PDT (-0700), Jeff Law wrote: > >>> I'd doubt it's worth the complexity.  Picking some reasonable value gets >>> you the vast majority of the benefit.   Something like >>> COSTS_N_INSNS(6) is enough to get CSE to trigger.  So what's left is a >>> reasonable cost, particularly for the division-by-constant case where we >>> need a ceiling for synth_mult. >> >> Ya, makes sense.  I noticed our multi-word multiply costs are a bit odd >> too (they really only work for 64-bit mul on 32-bit targets), but that's >> probably not worth worrying about either. > We do have a changes locally that adjust various costs. One of which is > highpart multiply. One of the many things to start working through once > gcc-15 opens for development. Hence my desire to help keep gcc-14 on > track for an on-time release. Cool. LMK if there's anything we can do to help on that front. > > Jeff