Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936959AbZAPUid (ORCPT ); Fri, 16 Jan 2009 15:38:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753167AbZAPUiX (ORCPT ); Fri, 16 Jan 2009 15:38:23 -0500 Received: from nlpi025.sbcis.sbc.com ([207.115.36.54]:58460 "EHLO nlpi025.prodigy.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752593AbZAPUiW (ORCPT ); Fri, 16 Jan 2009 15:38:22 -0500 Date: Fri, 16 Jan 2009 14:37:32 -0600 (CST) From: Christoph Lameter X-X-Sender: cl@quilx.com To: Richard Henderson cc: Rusty Russell , Ingo Molnar , akpm@linux-foundation.org, torvalds@linux-foundation.org, andi@firstfloor.org, ak@linux.intel.com, sfr@canb.auug.org.au, travis@sgi.com, linux-kernel@vger.kernel.org Subject: Re: [patch 2/8] compiler-gcc.h: add more comments to RELOC_HIDE In-Reply-To: <496FC375.90408@twiddle.net> Message-ID: References: <200901100040.n0A0eruc013680@imap1.linux-foundation.org> <20090110122945.GA28033@elte.hu> <200901151227.27935.rusty@rustcorp.com.au> <496FC375.90408@twiddle.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Spam-Score: -2.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1199 Lines: 29 On Thu, 15 Jan 2009, Richard Henderson wrote: > I didn't explore the space of possible solutions, merely gave Rusty a solution > that I knew would work, and would never fail because the compiler would never > look through the asm. > > I wouldn't be surprised if the compiler thought "(long)&foo - large_constant" > could be put back together into a small-data relocation, simply because at the > level at which that optimization is performed, we've thrown away type data > like long and void*; we only have modes. We are talking about (long)&foo + long_variable Are you saying that the compiler will be ignoring the high bits in variable because of the size of foo? > Why are you wanting to change this at all? It works as it is. It looks like its useless and more an indication of either a broken compiler or wrong assumptions about the compiler. Removing RELOC_HIDE should allow the compiler to freely optimize the per cpu address calculations. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/