From nobody Wed Aug 26 07:48:17 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=ziglang.org ARC-Seal: i=1; a=rsa-sha256; t=1785849425; cv=none; d=zohomail.com; s=zohoarc; b=gX4uUk3di7LtTS1xdRhkv0molQeohVVz4nREEJFbq0CG6bptkiBjtApsSoWWOKyOhyfI9wTL1q/e2rDWDM5wZ0+ebqGZAd2AMArxmGb0UrfaSbhVlqFpOLHiMLIpZF5n/uLX2heGlBB4DXipk1du9h/23cCgp5+FpchzBJjno2M= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1785849425; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=SnbJVNe3T6XZa7Vk/Urh3e8MfFhkWSymJI2RcI5QY48=; b=Gz3dXTP7cKyaPgGSm+S8IeN+PsQLfqDcYA1WQe7sSUBnoow/czBlOfqHNTqir355hxQoVg/3nrEQdOsoqNu+4E66wFKfogT5HOA4ZgkuFwKVsI+bY+U2Mezp5FZehMVK3OpjKWFdK57PG8za6WbU8mjoKhoPwHigsMUt2VWrVGI= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1785849425543271.89565935522785; Tue, 4 Aug 2026 06:17:05 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wrF0a-000598-R1; Tue, 04 Aug 2026 09:16:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wr8eV-00016b-SF for qemu-devel@nongnu.org; Tue, 04 Aug 2026 02:29:27 -0400 Received: from mail.ziglang.org ([108.61.23.47]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wr8eU-0004bY-GQ for qemu-devel@nongnu.org; Tue, 04 Aug 2026 02:29:27 -0400 From: Jacob Young DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ziglang.org; s=mail; t=1785824965; bh=gc84vgb2W4xTObRjAYWW1Xv+TZyjLcRjlC87tPKM4Pg=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=WNGXwkWhKlZmA8AQ3b3l/6goj/0HGetckY+S2RbB9q06O0LjHSU+ja1q3Ax34LROg 9qyyqsCmQ0/M0n6U4M/61njE+mJlLlnOLvlUEdgFxt5KSZe8nUE/S8LrbA/TRQYKR2 aLGxaKwmmrPmAkPKL1PMkhFvlPWYebW/7m+M+ax8= Date: Tue, 04 Aug 2026 02:27:23 -0400 Subject: [PATCH] tcg/optimize: Fix s_mask computation for shifts MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260804-fix-shift-smask-v1-1-8ce16b4000d1@ziglang.org> References: <20260804-fix-shift-smask-v1-0-8ce16b4000d1@ziglang.org> In-Reply-To: <20260804-fix-shift-smask-v1-0-8ce16b4000d1@ziglang.org> To: qemu-devel@nongnu.org Cc: Richard Henderson , Jacob Young Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; Received-SPF: pass client-ip=108.61.23.47; envelope-from=jacobly@ziglang.org; helo=mail.ziglang.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Tue, 04 Aug 2026 09:15:48 -0400 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @ziglang.org) X-ZM-MESSAGEID: 1785849426688158500 Previously, we would produce an incorrect smask in this case: t1.smask =3D 0xffffffff80000000 shr_i32 t0,t1,$0x1 t0.smask =3D 0xffffffffc0000000 because `do_constant_folding` would produce `smask =3D 0x40000000` which was passed unchanged to `fold_masks_zos` which would then update with `s_mask |=3D INT32_MIN;`, producing the incorrect result above. Reproducer (i386 assembly): .text .globl _start _start: movw $0x4000, %ax addw %ax, %ax cwtl shrl %eax xorl %ebx, %ebx cmpw $-0x3fff, %ax setnl %bl movl $1, %eax int $0x80 Signed-off-by: Jacob Young --- tcg/optimize.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/tcg/optimize.c b/tcg/optimize.c index fcdef25bee..96f7841afa 100644 --- a/tcg/optimize.c +++ b/tcg/optimize.c @@ -2658,6 +2658,14 @@ static bool fold_shift(OptContext *ctx, TCGOp *op) o_mask =3D do_constant_folding(op->opc, ctx->type, o_mask, sh); s_mask =3D do_constant_folding(op->opc, ctx->type, s_mask, sh); =20 + /* + * If the bit shifted into the result sign was not in the + * input s_mask, then no bits are known to match it. + */ + if ((int64_t)s_mask >=3D 0) { + s_mask =3D 0; + } + return fold_masks_zos(ctx, op, z_mask, o_mask, s_mask); } =20 --=20 2.55.0