From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 40D76C433ED for ; Sun, 18 Apr 2021 15:32:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 13B14610C7 for ; Sun, 18 Apr 2021 15:32:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231578AbhDRPdO (ORCPT ); Sun, 18 Apr 2021 11:33:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229998AbhDRPdO (ORCPT ); Sun, 18 Apr 2021 11:33:14 -0400 Received: from mail-ej1-x634.google.com (mail-ej1-x634.google.com [IPv6:2a00:1450:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE0BDC061760 for ; Sun, 18 Apr 2021 08:32:45 -0700 (PDT) Received: by mail-ej1-x634.google.com with SMTP id w3so49152530ejc.4 for ; Sun, 18 Apr 2021 08:32:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=7mTDPMx1aYnlOGqFSax2OjMQRk5DqmfeLh7StN5YDao=; b=AYyXUBCcAkNlhSYgaQQpX4jt4zH+4iPY23zkCGcYj5onmv7abAlfJ+Tu1ob2Lu/nb4 QsDH0rs3Cm1DNlyRFGuQKG59A+RadmKJ43v7IiLcaiuVqt1m+q+tLQ1/hL5B1ywOkO4D g8sJkMevzUS5j3/s9NBzgxTL4dLyFF/K9AMtTq2NUho0oPgi3+3wDbwz5LEVGb1WVabK 2scuJpLTnkmVW/GW04JD0RqLK0fjJEjhrAStOnS6y8R8L7dP5ut+B44oAyoAWI8emmg8 ZskDRrJNJNhxUzmsBq+N8cnuIn28fUrwDsDlBTge9x63KDbnr2saHbb+8XU/WYyWoUl7 CPGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=7mTDPMx1aYnlOGqFSax2OjMQRk5DqmfeLh7StN5YDao=; b=qt1dCHgeMDu2bcyjewNpbptN+KveKjLUoguRbImaizZ5gC5gjvulzL3sndvOxbsm/1 nmqk3d7dOYANPaOgSa+wE19UYL7Lat4h/8P1ZPZXIHnjNpvVKWQ4ZGOrFSSJSlx85PYG 1pePMm0g6M3wH5E/PmdSECUbWSqZv/O0yTdEJtVsj9UEtoaXrpuppiz8hptxTI+nBvwN NmfR3jmezsPzUaSvo6aVSc02tdqBdObFvv5O2gw7YJpBNkvXBeNYSnusTn/g8c8lzujB 0aAe2QS7FN7loK5ezYYjpSfYL9DE0BVx4Lft9ReME2XXokF4I9cesUhwvPmTh+6vRZhD pmiQ== X-Gm-Message-State: AOAM530BOGL+9PJdgct3fJVkXfbQ6esAaub0YqlrYMD2IDGqWGS2YAmC +uSMxV3GdiYHpKzoVa4IcaUkuEoR14Q= X-Google-Smtp-Source: ABdhPJwmW/etaUp8vOnoZZNXQ31OuEQ6Bq4V4FiecS+Z2zeIyIVDzGTyHSH8RU7SL+ZGX+7P/a64AA== X-Received: by 2002:a17:906:b01:: with SMTP id u1mr18192508ejg.310.1618759964502; Sun, 18 Apr 2021 08:32:44 -0700 (PDT) Received: from localhost.localdomain ([2a02:a03f:b7fe:f700:959c:c85:d486:38cf]) by smtp.gmail.com with ESMTPSA id k9sm8632888eje.102.2021.04.18.08.32.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 18 Apr 2021 08:32:44 -0700 (PDT) From: Luc Van Oostenryck To: linux-sparse@vger.kernel.org Cc: Linus Torvalds , Luc Van Oostenryck Subject: [SPARSE 1/4] canonicalize constant signed compares toward zero Date: Sun, 18 Apr 2021 17:32:30 +0200 Message-Id: <20210418153233.45234-2-luc.vanoostenryck@gmail.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210418153233.45234-1-luc.vanoostenryck@gmail.com> References: <20210418153233.45234-1-luc.vanoostenryck@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-sparse@vger.kernel.org Currently, signed compares against a constant are canonicalized toward the smallest possible constant. So, the following canonicalization are done: x < 256 --> x <= 255 x < -2047 --> x <= -2048 This has two advantages: 1) it maximalizes the number of constants possible for a given bit size. 2) it allows to remove all < and all >= But it has also a serious disadvantages: a simple comparison against zero, like: x >= 0 is canonicalized into: x > -1 Which can be more costly for some architectures if translated as such , is also less readable than the version using 0 and is also sometimes quite more complicated to match in some simplification patterns. So, canonicalize it using 'towards 0' / using the smallest constant in absolute value. Signed-off-by: Luc Van Oostenryck --- simplify.c | 34 +++++++++--- validation/optim/canonical-cmp-zero.c | 74 +++++++++++++++++++++++++++ 2 files changed, 102 insertions(+), 6 deletions(-) create mode 100644 validation/optim/canonical-cmp-zero.c diff --git a/simplify.c b/simplify.c index 9e3514d838a9..e0e4f9ebcba9 100644 --- a/simplify.c +++ b/simplify.c @@ -1178,38 +1178,52 @@ static int simplify_compare_constant(struct instruction *insn, long long value) switch (insn->opcode) { case OP_SET_LT: + if (!value) + break; if (value == sign_bit(size)) // (x < SMIN) --> 0 return replace_with_pseudo(insn, value_pseudo(0)); if (value == sign_mask(size)) // (x < SMAX) --> (x != SMAX) return replace_opcode(insn, OP_SET_NE); if (value == sign_bit(size) + 1)// (x < SMIN + 1) --> (x == SMIN) return replace_binop_value(insn, OP_SET_EQ, sign_bit(size)); - changed |= replace_binop_value(insn, OP_SET_LE, (value - 1) & bits); + if (!(value & sign_bit(size))) + changed |= replace_binop_value(insn, OP_SET_LE, (value - 1) & bits); break; case OP_SET_LE: + if (!value) + break; if (value == sign_mask(size)) // (x <= SMAX) --> 1 return replace_with_pseudo(insn, value_pseudo(1)); if (value == sign_bit(size)) // (x <= SMIN) --> (x == SMIN) return replace_opcode(insn, OP_SET_EQ); if (value == sign_mask(size) - 1) // (x <= SMAX - 1) --> (x != SMAX) return replace_binop_value(insn, OP_SET_NE, sign_mask(size)); + if (value & sign_bit(size)) + changed |= replace_binop_value(insn, OP_SET_LT, (value + 1) & bits); break; case OP_SET_GE: + if (!value) + break; if (value == sign_bit(size)) // (x >= SMIN) --> 1 return replace_with_pseudo(insn, value_pseudo(1)); if (value == sign_mask(size)) // (x >= SMAX) --> (x == SMAX) return replace_opcode(insn, OP_SET_EQ); if (value == sign_bit(size) + 1)// (x >= SMIN + 1) --> (x != SMIN) return replace_binop_value(insn, OP_SET_NE, sign_bit(size)); - changed |= replace_binop_value(insn, OP_SET_GT, (value - 1) & bits); + if (!(value & sign_bit(size))) + changed |= replace_binop_value(insn, OP_SET_GT, (value - 1) & bits); break; case OP_SET_GT: + if (!value) + break; if (value == sign_mask(size)) // (x > SMAX) --> 0 return replace_with_pseudo(insn, value_pseudo(0)); if (value == sign_bit(size)) // (x > SMIN) --> (x != SMIN) return replace_opcode(insn, OP_SET_NE); if (value == sign_mask(size) - 1) // (x > SMAX - 1) --> (x == SMAX) return replace_binop_value(insn, OP_SET_EQ, sign_mask(size)); + if (value & sign_bit(size)) + changed |= replace_binop_value(insn, OP_SET_GE, (value + 1) & bits); break; case OP_SET_B: @@ -1271,8 +1285,10 @@ static int simplify_compare_constant(struct instruction *insn, long long value) if ((value & bits) != value) return replace_with_value(insn, 1); break; - case OP_SET_LE: + case OP_SET_LE: case OP_SET_LT: value = sign_extend(value, def->size); + if (insn->opcode == OP_SET_LT) + value -= 1; if (bits & sign_bit(def->size)) break; if (value < 0) @@ -1282,8 +1298,10 @@ static int simplify_compare_constant(struct instruction *insn, long long value) if (value == 0) return replace_opcode(insn, OP_SET_EQ); break; - case OP_SET_GT: + case OP_SET_GT: case OP_SET_GE: value = sign_extend(value, def->size); + if (insn->opcode == OP_SET_GE) + value -= 1; if (bits & sign_bit(def->size)) break; if (value < 0) @@ -1340,16 +1358,20 @@ static int simplify_compare_constant(struct instruction *insn, long long value) if (bits >= value) return replace_with_value(insn, 1); break; + case OP_SET_LT: + value -= 1; case OP_SET_LE: - value = sign_extend(value, def->size); if (bits & sign_bit(def->size)) { + value = sign_extend(value, def->size); if (value >= -1) return replace_with_value(insn, 1); } break; + case OP_SET_GE: + value -= 1; case OP_SET_GT: - value = sign_extend(value, def->size); if (bits & sign_bit(def->size)) { + value = sign_extend(value, def->size); if (value >= -1) return replace_with_value(insn, 0); } diff --git a/validation/optim/canonical-cmp-zero.c b/validation/optim/canonical-cmp-zero.c new file mode 100644 index 000000000000..e01a00e637b6 --- /dev/null +++ b/validation/optim/canonical-cmp-zero.c @@ -0,0 +1,74 @@ +int f00(int x) { return x >= 0; } +int f01(int x) { return x > -1; } +int f02(int x) { return x < 1; } +int f03(int x) { return x <= 0; } + +int f10(int x) { return x < 16; } +int f11(int x) { return x <= 15; } + +int f20(int x) { return x > -9; } +int f21(int x) { return x >= -8; } + +/* + * check-name: canonical-cmp-zero + * check-command: test-linearize -Wno-decl $file + * + * check-output-start +f00: +.L0: + + setge.32 %r2 <- %arg1, $0 + ret.32 %r2 + + +f01: +.L2: + + setge.32 %r5 <- %arg1, $0 + ret.32 %r5 + + +f02: +.L4: + + setle.32 %r8 <- %arg1, $0 + ret.32 %r8 + + +f03: +.L6: + + setle.32 %r11 <- %arg1, $0 + ret.32 %r11 + + +f10: +.L8: + + setle.32 %r14 <- %arg1, $15 + ret.32 %r14 + + +f11: +.L10: + + setle.32 %r17 <- %arg1, $15 + ret.32 %r17 + + +f20: +.L12: + + setge.32 %r20 <- %arg1, $0xfffffff8 + ret.32 %r20 + + +f21: +.L14: + + setge.32 %r23 <- %arg1, $0xfffffff8 + ret.32 %r23 + + + * check-output-end + */ -- 2.31.1