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{ "id": 2232137, "url": "http://patchwork.ozlabs.org/api/covers/2232137/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/cover/20260503053451.48504-1-herumi@nifty.com/", "project": { "id": 17, "url": "http://patchwork.ozlabs.org/api/projects/17/?format=api", "name": "GNU Compiler Collection", "link_name": "gcc", "list_id": "gcc-patches.gcc.gnu.org", "list_email": "gcc-patches@gcc.gnu.org", "web_url": null, "scm_url": null, "webscm_url": null, "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260503053451.48504-1-herumi@nifty.com>", "list_archive_url": null, "date": "2026-05-03T05:34:48", "name": "[v2,0/3] Optimize 32-bit unsigned constant division for 64-bit targets", "submitter": { "id": 92964, "url": "http://patchwork.ozlabs.org/api/people/92964/?format=api", "name": null, "email": "herumi@nifty.com" }, "mbox": "http://patchwork.ozlabs.org/project/gcc/cover/20260503053451.48504-1-herumi@nifty.com/mbox/", "series": [ { "id": 502562, "url": "http://patchwork.ozlabs.org/api/series/502562/?format=api", "web_url": "http://patchwork.ozlabs.org/project/gcc/list/?series=502562", "date": "2026-05-03T05:34:51", "name": "Optimize 32-bit unsigned constant division for 64-bit targets", "version": 2, "mbox": "http://patchwork.ozlabs.org/series/502562/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/covers/2232137/comments/", "headers": { "Return-Path": "<gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "gcc-patches@gcc.gnu.org" ], "Delivered-To": [ "patchwork-incoming@legolas.ozlabs.org", "gcc-patches@gcc.gnu.org" ], "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=nifty.com header.i=@nifty.com header.a=rsa-sha256\n header.s=default-1th84yt82rvi header.b=t5rr0gKo;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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c=relaxed/simple;\n bh=6xdcfpDiybYQLZ68dBW6YlhNG0VQ+5HI/O9yy79c5qc=;\n h=From:To:Subject:Date:Message-ID:MIME-Version:DKIM-Signature;\n b=iFQKOopKSXmzO4C00j7gL1go+jiujqQXZjlvjO6NYRJKDU2QbzgS8ktP/sG4xsY68G0m3PbeqcBQ2J35JH1cLhf7YrwF0vxpuuB6+lb8VKe90vIcQ1UvHMsZ/AR+lJFZsCQARU23HV/zn1X+YZLa96C3000UNmlXhwvXp+UIUFQ=", "ARC-Authentication-Results": "i=1; server2.sourceware.org", "From": "herumi@nifty.com", "To": "gcc-patches@gcc.gnu.org", "Cc": "rguenther@suse.de, jeffreyalaw@gmail.com, ubizjak@gmail.com,\n MITSUNARI Shigeo <herumi@nifty.com>", "Subject": "[PATCH v2 0/3] Optimize 32-bit unsigned constant division for 64-bit\n targets", "Date": "Sun, 3 May 2026 14:34:48 +0900", "Message-ID": "<20260503053451.48504-1-herumi@nifty.com>", "X-Mailer": "git-send-email 2.43.0", "In-Reply-To": "<727728f8-76e5-457b-ab9f-d650550e0702@gmail.com>", "References": "<727728f8-76e5-457b-ab9f-d650550e0702@gmail.com>", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com;\n s=default-1th84yt82rvi; t=1777786529;\n bh=fd7rht+IvbAwrYd3C92JvlLFmZSfpGT8yUmNGjkdFK0=;\n h=From:To:Cc:Subject:Date:In-Reply-To:References;\n b=t5rr0gKokbq+rRsjGkuAGA6Fiz11rKdHyyBDJA1MdvjkRMJcGI5MjhAmQnHxcwxfqUwXheZq\n vjQ0Zgu5SIeryG6EAshRPWu8ynXI3gUnvOuf6zh/d2osK+1ErHJr5oQlMOTgLxjm1F+KPnt1fp\n V36rd+DtTLqGQymUIMtM5VaL5i5nb4jzGpnQ+zmh4ls2YdztqKzhBM/VLntY9RL1zDRy6Pu0QW\n 3Z7UnQ35pn5upuKIZ954dVgBrkbmxVfNlOgb0mtvw8nb7u5uwAFpMkV3vE3PPejaux9u2uqOT+\n pxNxMrJvCZSvN3jRyEEGdJVqxm43kYkiTgPQG8NvpEH85X/A==", "X-BeenThere": "gcc-patches@gcc.gnu.org", "X-Mailman-Version": "2.1.30", "Precedence": "list", "List-Id": "Gcc-patches mailing list <gcc-patches.gcc.gnu.org>", "List-Unsubscribe": "<https://gcc.gnu.org/mailman/options/gcc-patches>,\n <mailto:gcc-patches-request@gcc.gnu.org?subject=unsubscribe>", "List-Archive": "<https://gcc.gnu.org/pipermail/gcc-patches/>", "List-Post": "<mailto:gcc-patches@gcc.gnu.org>", "List-Help": "<mailto:gcc-patches-request@gcc.gnu.org?subject=help>", "List-Subscribe": "<https://gcc.gnu.org/mailman/listinfo/gcc-patches>,\n <mailto:gcc-patches-request@gcc.gnu.org?subject=subscribe>", "Errors-To": "gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org" }, "content": "From: MITSUNARI Shigeo <herumi@nifty.com>\n\nCompiler optimization for constant division of `uint32_t` variables (e.g.,\n`x / 7`) is based on the Granlund-Montgomery (GM) method [1].\nWhen the magic multiplier requires 33 bits (`mh != 0`), the GM method uses a\nsub/shift/add sequence designed for 32-bit registers.\nThis patch pre-shifts the 33-bit magic constant into a 64-bit value and uses a\nsingle 64x64->128-bit high-part multiply to obtain the quotient directly,\neliminating the post-multiply add/sub/shift sequence.\n\nOn x86_64, `x / 7` is reduced from 7 instructions to 4 (or 3 with BMI2).\nA benchmark on Xeon w9-3495X shows a 1.67x speedup.\n\nChanges in v2:\n- Rebased on current master (post GCC 16 release).\n\nAffected divisors: 32-bit unsigned constant divisors where `mh != 0`\n(7, 19, 21, 27, 31, 35, 37, 107, etc.)\nArchitectures: 64-bit or wider targets with 64x64->128-bit high-part multiply\n(x86_64, AArch64, RISC-V64, etc.)\npatch2, patch3: x86_64 BMI2 targets only.\n\nTesting: Ran `make check-gcc RUNTESTFLAGS=\"i386.exp\"` before and after applying\nthe patches. The results are identical.\n\nNote: The same optimization technique has been applied to LLVM and merged into\nllvm:main at https://github.com/llvm/llvm-project/pull/181288.\n\nReferences:\n[1] T. Granlund, P. L. Montgomery, \"Division by Invariant Integers using\n Multiplication\", PLDI 1994\n[2] https://arxiv.org/abs/2604.07902\n\nMITSUNARI Shigeo (3):\n expmed: Optimize 32-bit unsigned division by constants on 64-bit\n targets\n i386: Add BMI2 MULX pattern for highpart-only multiplication\n i386: Add peephole2 to convert highpart mul to mulx\n\n gcc/config/i386/i386.md | 32 +++++++++++++++\n gcc/expmed.cc | 86 +++++++++++++++++++++++++++++------------\n 2 files changed, 93 insertions(+), 25 deletions(-)" }