From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3180 invoked by alias); 5 Mar 2008 11:11:14 -0000 Received: (qmail 2497 invoked by uid 48); 5 Mar 2008 11:10:31 -0000 Date: Wed, 05 Mar 2008 11:11:00 -0000 Message-ID: <20080305111031.2496.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug rtl-optimization/35281] [4.3/4.4 Regression] multiply with 0 generated for 64*32->64 In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "ubizjak at gmail dot com" Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2008-03/txt/msg00310.txt.bz2 ------- Comment #7 from ubizjak at gmail dot com 2008-03-05 11:10 ------- It looks that: 2006-11-03 Paolo Bonzini Steven Bosscher * fwprop.c: New file. ... * cse.c (fold_rtx_subreg, fold_rtx_mem, fold_rtx_mem_1, find_best_addr, canon_for_address, table_size): Remove. (new_basic_block, insert, remove_from_table): Remove references to table_size. (fold_rtx): Process SUBREGs and MEMs with equiv_constant, make simplification loop more straightforward by not calling fold_rtx recursively. (equiv_constant): Move here a small part of fold_rtx_subreg, do not call fold_rtx. Call avoid_constant_pool_reference to process MEMs. removed this functionality. Specifically this part: - /* If this is a constant pool reference, we can fold it into its - constant to allow better value tracking. */ - if (base && GET_CODE (base) == SYMBOL_REF - && CONSTANT_POOL_ADDRESS_P (base)) - { - rtx constant = get_pool_constant (base); - enum machine_mode const_mode = get_pool_mode (base); - rtx new; - - if (CONSTANT_P (constant) && GET_CODE (constant) != CONST_INT) - { - constant_pool_entries_cost = COST (constant); - constant_pool_entries_regcost = approx_reg_cost (constant); - } - - /* If we are loading the full constant, we have an - equivalence. */ - if (offset == 0 && mode == const_mode) - return constant; - - /* If this actually isn't a constant (weird!), we can't do - anything. Otherwise, handle the two most common cases: - extracting a word from a multi-word constant, and - extracting the low-order bits. Other cases don't seem - common enough to worry about. */ - if (! CONSTANT_P (constant)) - return x; - - if (GET_MODE_CLASS (mode) == MODE_INT - && GET_MODE_SIZE (mode) == UNITS_PER_WORD - && offset % UNITS_PER_WORD == 0 - && (new = operand_subword (constant, - offset / UNITS_PER_WORD, - 0, const_mode)) != 0) - return new; - - if (((BYTES_BIG_ENDIAN - && offset == GET_MODE_SIZE (GET_MODE (constant)) - 1) - || (! BYTES_BIG_ENDIAN && offset == 0)) - && (new = gen_lowpart (mode, constant)) != 0) - return new; - } This also explains why 4.2 doesn't fold HImode references ("Other cases don't seem common enough to worry about."). Can we have this functionality back, perhaps also for "Other cases", since there are people that worry about them? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35281