From mboxrd@z Thu Jan 1 00:00:00 1970 From: Luc Van Oostenryck Subject: [PATCH v2 7/8] transform (A << S) >> S into A & (-1 >> S) Date: Mon, 7 Aug 2017 21:12:04 +0200 Message-ID: <20170807191205.86590-8-luc.vanoostenryck@gmail.com> References: <20170807191205.86590-1-luc.vanoostenryck@gmail.com> Return-path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:38359 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927AbdHGTMT (ORCPT ); Mon, 7 Aug 2017 15:12:19 -0400 Received: by mail-wm0-f66.google.com with SMTP id y206so2036310wmd.5 for ; Mon, 07 Aug 2017 12:12:18 -0700 (PDT) In-Reply-To: <20170807191205.86590-1-luc.vanoostenryck@gmail.com> Sender: linux-sparse-owner@vger.kernel.org List-Id: linux-sparse@vger.kernel.org To: Dibyendu Majumdar Cc: linux-sparse@vger.kernel.org, Luc Van Oostenryck This is especially usefull when simplifying code accessing bitfields. Signed-off-by: Luc Van Oostenryck --- simplify.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/simplify.c b/simplify.c index f1a898700..cdc244c17 100644 --- a/simplify.c +++ b/simplify.c @@ -416,6 +416,7 @@ static int simplify_lsr(struct instruction *insn, pseudo_t pseudo, long long val { struct instruction *def; unsigned long long mask; + pseudo_t old; if (!value) return replace_with_pseudo(insn, pseudo); @@ -434,6 +435,20 @@ static int simplify_lsr(struct instruction *insn, pseudo_t pseudo, long long val insn->opcode = OP_AND; insn->src2 = value_pseudo(mask >> value); return REPEAT_CSE; + case OP_SHL: + // replace (A << S) >> S + // by A & (-1 >> S) + def = insn->src1->def; + if (!constant(def->src2)) + break; + if (def->src2->value != value) + break; + insn->opcode = OP_AND; + insn->src2 = value_pseudo(-1ULL >> value); + old = insn->src1; + use_pseudo(insn, def->src1, &insn->src1); + remove_usage(old, &insn->src1); + return REPEAT_CSE; } return 0; } -- 2.13.2