From patchwork Wed Nov 24 08:35:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Jelinek X-Patchwork-Id: 48052 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 7DDD23858000 for ; Wed, 24 Nov 2021 08:36:19 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7DDD23858000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1637742979; bh=Y8X3cxzwoOS0jjEfaraTPiGy4OaoHGFREnhdmvDAB+I=; h=Date:To:Subject:References:In-Reply-To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=x8yLi4DnNHLUF0BriHj9chtMSKQt6pthIcDjG4HrSVh9CVw6kto7hV/DhDSlErpdl 9CiYHjG1WzwGyXw/2GN53C5lAUFzhXORGqwRX5PqUo7qjgUbP5bE+9wDa59uQJGf9w eWOZmE42qR55juxrWeEQe3tz/zsSlQb/sx43Gnvo= X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 27229385841B for ; Wed, 24 Nov 2021 08:35:49 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 27229385841B Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-590-gaGHw6fBNau99ybtJ5DunQ-1; Wed, 24 Nov 2021 03:35:45 -0500 X-MC-Unique: gaGHw6fBNau99ybtJ5DunQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7938B81CCB4; Wed, 24 Nov 2021 08:35:44 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F35EF13AA5; Wed, 24 Nov 2021 08:35:43 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.16.1/8.16.1) with ESMTPS id 1AO8ZehU3985142 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 24 Nov 2021 09:35:41 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 1AO8Zdoq3985141; Wed, 24 Nov 2021 09:35:39 +0100 Date: Wed, 24 Nov 2021 09:35:39 +0100 To: Richard Biener , Roger Sayle Subject: [PATCH] bswap: Fix up symbolic merging for xor and plus [PR103376] Message-ID: <20211124083539.GI2646553@tucnak> References: <001601d7df7c$7f739920$7e5acb60$@nextmovesoftware.com> MIME-Version: 1.0 In-Reply-To: <001601d7df7c$7f739920$7e5acb60$@nextmovesoftware.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-5.7 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Jakub Jelinek via Gcc-patches From: Jakub Jelinek Reply-To: Jakub Jelinek Cc: gcc-patches@gcc.gnu.org Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" On Mon, Nov 22, 2021 at 08:39:42AM -0000, Roger Sayle wrote: > This patch implements PR tree-optimization/103345 to merge adjacent > loads when combined with addition or bitwise xor. The current code > in gimple-ssa-store-merging.c's find_bswap_or_nop alreay handles ior, > so that all that's required is to treat PLUS_EXPR and BIT_XOR_EXPR in > the same way at BIT_IOR_EXPR. Unfortunately they aren't exactly the same. They work the same if always at least one operand (or corresponding byte in it) is known to be 0, 0 | 0 = 0 ^ 0 = 0 + 0 = 0. But for | also x | x = x for any other x, so perform_symbolic_merge has been accepting either that at least one of the bytes is 0 or that both are the same, but that is wrong for ^ and +. The following patch fixes that by passing through the code of binary operation and allowing non-zero masked1 == masked2 through only for BIT_IOR_EXPR. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? Thinking more about it, perhaps we could do more for BIT_XOR_EXPR. We could allow masked1 == masked2 case for it, but would need to do something different than the n->n = n1->n | n2->n; we do on all the bytes together. In particular, for masked1 == masked2 if masked1 != 0 (well, for 0 both variants are the same) and masked1 != 0xff we would need to clear corresponding n->n byte instead of setting it to the input as x ^ x = 0 (but if we don't know what x and y are, the result is also don't know). Now, for plus it is much harder, because not only for non-zero operands we don't know what the result is, but it can modify upper bytes as well. So perhaps only if current's byte masked1 && masked2 set the resulting byte to 0xff (unknown) iff the byte above it is 0 and 0, and set that resulting byte to 0xff too. Also, even for | we could instead of return NULL just set the resulting byte to 0xff if it is different, perhaps it will be masked off later on. Ok to handle that incrementally? 2021-11-24 Jakub Jelinek PR tree-optimization/103376 * gimple-ssa-store-merging.c (perform_symbolic_merge): Add CODE argument. If CODE is not BIT_IOR_EXPR, ensure that one of masked1 or masked2 is 0. (find_bswap_or_nop_1, find_bswap_or_nop, imm_store_chain_info::try_coalesce_bswap): Adjust perform_symbolic_merge callers. * gcc.c-torture/execute/pr103376.c: New test. Jakub --- gcc/gimple-ssa-store-merging.c.jj 2021-11-23 10:26:30.000000000 +0100 +++ gcc/gimple-ssa-store-merging.c 2021-11-23 11:49:33.806168782 +0100 @@ -434,14 +434,14 @@ find_bswap_or_nop_load (gimple *stmt, tr return true; } -/* Compute the symbolic number N representing the result of a bitwise OR on 2 - symbolic number N1 and N2 whose source statements are respectively - SOURCE_STMT1 and SOURCE_STMT2. */ +/* Compute the symbolic number N representing the result of a bitwise OR, + bitwise XOR or plus on 2 symbolic number N1 and N2 whose source statements + are respectively SOURCE_STMT1 and SOURCE_STMT2. CODE is the operation. */ gimple * perform_symbolic_merge (gimple *source_stmt1, struct symbolic_number *n1, gimple *source_stmt2, struct symbolic_number *n2, - struct symbolic_number *n) + struct symbolic_number *n, enum tree_code code) { int i, size; uint64_t mask; @@ -563,7 +563,9 @@ perform_symbolic_merge (gimple *source_s masked1 = n1->n & mask; masked2 = n2->n & mask; - if (masked1 && masked2 && masked1 != masked2) + /* For BIT_XOR_EXPR or PLUS_EXPR, at least one of masked1 and masked2 + has to be 0, for BIT_IOR_EXPR x | x is still x. */ + if (masked1 && masked2 && (code != BIT_IOR_EXPR || masked1 != masked2)) return NULL; } n->n = n1->n | n2->n; @@ -769,7 +771,8 @@ find_bswap_or_nop_1 (gimple *stmt, struc return NULL; source_stmt - = perform_symbolic_merge (source_stmt1, &n1, source_stmt2, &n2, n); + = perform_symbolic_merge (source_stmt1, &n1, source_stmt2, &n2, n, + code); if (!source_stmt) return NULL; @@ -943,7 +946,8 @@ find_bswap_or_nop (gimple *stmt, struct else if (!do_shift_rotate (LSHIFT_EXPR, &n0, eltsz)) return NULL; ins_stmt - = perform_symbolic_merge (ins_stmt, &n0, source_stmt, &n1, n); + = perform_symbolic_merge (ins_stmt, &n0, source_stmt, &n1, n, + BIT_IOR_EXPR); if (!ins_stmt) return NULL; @@ -2881,7 +2885,7 @@ imm_store_chain_info::try_coalesce_bswap end = MAX (end, info->bitpos + info->bitsize); ins_stmt = perform_symbolic_merge (ins_stmt, &n, info->ins_stmt, - &this_n, &n); + &this_n, &n, BIT_IOR_EXPR); if (ins_stmt == NULL) return false; } --- gcc/testsuite/gcc.c-torture/execute/pr103376.c.jj 2021-11-23 12:03:38.339948150 +0100 +++ gcc/testsuite/gcc.c-torture/execute/pr103376.c 2021-11-23 12:02:44.668723595 +0100 @@ -0,0 +1,29 @@ +/* PR tree-optimization/103376 */ + +long long a = 0x123456789abcdef0LL, f; +int b, c, *d; + +__attribute__((noipa)) void +foo (int x) +{ + asm volatile ("" : : "r" (x)); +} + +int +main () +{ + long long e; + e = a; + if (b) + { + foo (c); + d = (int *) 0; + while (*d) + ; + } + f = a ^ e; + asm volatile ("" : "+m" (f)); + if (f != 0) + __builtin_abort (); + return 0; +}