From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 06A0D3858D39 for ; Wed, 1 Feb 2023 09:03:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 06A0D3858D39 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675242183; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=aX8X/xO5V5ykyqrmCuakBK3XPdNKyHkiLRFqPU/x8UY=; b=EySRJ4GjTUcs2GYpWnEBIqUT2njTZ+e66bP5U+jJw34+3YSqxP+n7bH4qelraYLN6WkHCN mvoZj/yvcFFOM+J4U1nh0c6fprUkSdc7UiPYcP3qp/tqCTQXmQggRURB/xIrOBzOUEXAom jG+CiRvhYJ3d9u510Cv8GC4TYDvoRMo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-231-NWkd5BYFNIqZhTxiDHZcHQ-1; Wed, 01 Feb 2023 04:01:55 -0500 X-MC-Unique: NWkd5BYFNIqZhTxiDHZcHQ-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6DF44100DEA1; Wed, 1 Feb 2023 09:01:51 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.223]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0FE21492B06; Wed, 1 Feb 2023 09:01:49 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.17.1/8.17.1) with ESMTPS id 31191isc3209322 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 1 Feb 2023 10:01:47 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 31191bdM3209319; Wed, 1 Feb 2023 10:01:37 +0100 Date: Wed, 1 Feb 2023 10:01:36 +0100 From: Jakub Jelinek To: Fangrui Song Cc: gcc-patches@gcc.gnu.org Subject: Re: [PATCH] x86: Use DW_EH_PE_indirect|DW_EH_PE_pcrel encodings for -fno-pic code Message-ID: Reply-To: Jakub Jelinek References: <20230201073859.3920910-1-maskray@google.com> MIME-Version: 1.0 In-Reply-To: <20230201073859.3920910-1-maskray@google.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-9.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,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 Tue, Jan 31, 2023 at 11:38:59PM -0800, Fangrui Song via Gcc-patches wrote: > Follow aarch64 and riscv ports by using (global ? DW_EH_PE_indirect : 0) > | DW_EH_PE_pcrel for -fno-pic code. This avoids a canonical PLT entry > for a personality reference in .eh_frame and a copy relocation for a > typeinfo reference in .gcc_except_table, when the definition is in > libstdc++.so.6. > > gcc/ > > PR target/108622 > * config/i386/i386.cc (asm_preferred_eh_data_format): Always use the > PIC encoding. Use DW_EH_PE_indirect if global. Not a review, just comments: > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc > index 3cacf738c4a..b572dd46a62 100644 > --- a/gcc/config/i386/i386.cc > +++ b/gcc/config/i386/i386.cc > @@ -22851,22 +22851,13 @@ ix86_stack_protect_fail (void) > int > asm_preferred_eh_data_format (int code, int global) > { > - /* PE-COFF is effectively always -fPIC because of the .reloc section. */ > - if (flag_pic || TARGET_PECOFF || !ix86_direct_extern_access) > - { > - int type = DW_EH_PE_sdata8; > - if (ptr_mode == SImode > - || ix86_cmodel == CM_SMALL_PIC > - || (ix86_cmodel == CM_MEDIUM_PIC && (global || code))) > - type = DW_EH_PE_sdata4; > - return (global ? DW_EH_PE_indirect : 0) | DW_EH_PE_pcrel | type; > - } > - > - if (ix86_cmodel == CM_SMALL > - || (ix86_cmodel == CM_MEDIUM && code)) > - return DW_EH_PE_udata4; > - > - return DW_EH_PE_absptr; > + int type = DW_EH_PE_sdata8; > + if (ptr_mode == SImode || ix86_cmodel == CM_SMALL || > + ix86_cmodel == CM_SMALL_PIC || > + (ix86_cmodel == CM_MEDIUM && code) || > + (ix86_cmodel == CM_MEDIUM_PIC && (global || code))) The above is incorrectly formatted, the GCC Coding Conventions say || etc. shouldn't be at the end of lines, but rather at the start of the next ones. And, while I can understand the rationale for global cases (though am not sure I agree, as currently the user can choose by using -mno-direct-extern-access or not using it, the above change disallows the choice), for !global I miss the point altogether. In non-PIC (and non-PECOFF maybe, don't know that format well) code if code references a local symbol, it will never generate a copy relocation and so DW_EH_PE_udata4 could be just fine and cheaper to handle on the consumer sides. Jakub