From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH] lib/raid6: Add AVX2 optimized recovery functions Date: Thu, 29 Nov 2012 12:09:37 -0800 Message-ID: References: <1352411264-5156-1-git-send-email-james.t.kukunas@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <1352411264-5156-1-git-send-email-james.t.kukunas@linux.intel.com> (Jim Kukunas's message of "Thu, 8 Nov 2012 13:47:44 -0800") Sender: linux-raid-owner@vger.kernel.org To: Jim Kukunas Cc: Linux Raid , Linux Kernel , Neil Brown , "H. Peter Anvin" List-Id: linux-raid.ids Jim Kukunas writes: > + > + /* ymm0 = x0f[16] */ > + asm volatile("vpbroadcastb %0, %%ymm7" : : "m" (x0f)); > + > + while (bytes) { > +#ifdef CONFIG_X86_64 > + asm volatile("vmovdqa %0, %%ymm1" : : "m" (q[0])); > + asm volatile("vmovdqa %0, %%ymm9" : : "m" (q[32])); > + asm volatile("vmovdqa %0, %%ymm0" : : "m" (p[0])); > + asm volatile("vmovdqa %0, %%ymm8" : : "m" (p[32])); This is somewhat dangerous to assume registers do not get changed between assembler statements or assembler statements do not get reordered. Better always put such values into explicit variables or merge them into a single asm statement. asm volatile is also not enough to prevent reordering. If anything you would need a memory clobber. -Andi -- ak@linux.intel.com -- Speaking for myself only