Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754598AbcDAKAr (ORCPT ); Fri, 1 Apr 2016 06:00:47 -0400 Received: from e23smtp04.au.ibm.com ([202.81.31.146]:39376 "EHLO e23smtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754119AbcDAKAp (ORCPT ); Fri, 1 Apr 2016 06:00:45 -0400 X-IBM-Helo: d23dlp03.au.ibm.com X-IBM-MailFrom: naveen.n.rao@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Naveen N. Rao" To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: oss@buserror.net, Matt Evans , Michael Ellerman , Paul Mackerras , Alexei Starovoitov , "David S. Miller" , Ananth N Mavinakayanahalli Subject: [RFC PATCH 1/6] ppc: bpf/jit: Fix/enhance 32-bit Load Immediate implementation Date: Fri, 1 Apr 2016 15:28:26 +0530 Message-Id: <770e1d46546d93be5248fb9d398bf57a925faa74.1459504223.git.naveen.n.rao@linux.vnet.ibm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: In-Reply-To: References: X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16040110-0013-0000-0000-000004A8C604 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2105 Lines: 53 The existing LI32() macro can sometimes result in a sign-extended 32-bit load that does not clear the top 32-bits properly. As an example, loading 0x7fffffff results in the register containing 0xffffffff7fffffff. While this does not impact classic BPF JIT implementation (since that only uses the lower word for all operations), we would like to share this macro between classic BPF JIT and extended BPF JIT, wherein the entire 64-bit value in the register matters. Fix this by first doing a shifted LI followed by ORI. An additional optimization is with loading values between -32768 to -1, where we now only need a single LI. The new implementation now generates the same or less number of instructions. Cc: Matt Evans Cc: Michael Ellerman Cc: Paul Mackerras Cc: Alexei Starovoitov Cc: "David S. Miller" Cc: Ananth N Mavinakayanahalli Signed-off-by: Naveen N. Rao --- arch/powerpc/net/bpf_jit.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h index 889fd19..a9882db 100644 --- a/arch/powerpc/net/bpf_jit.h +++ b/arch/powerpc/net/bpf_jit.h @@ -232,10 +232,17 @@ DECLARE_LOAD_FUNC(sk_load_byte_msh); (((cond) & 0x3ff) << 16) | \ (((dest) - (ctx->idx * 4)) & \ 0xfffc)) -#define PPC_LI32(d, i) do { PPC_LI(d, IMM_L(i)); \ - if ((u32)(uintptr_t)(i) >= 32768) { \ - PPC_ADDIS(d, d, IMM_HA(i)); \ +/* Sign-extended 32-bit immediate load */ +#define PPC_LI32(d, i) do { \ + if ((int)(uintptr_t)(i) >= -32768 && \ + (int)(uintptr_t)(i) < 32768) \ + PPC_LI(d, i); \ + else { \ + PPC_LIS(d, IMM_H(i)); \ + if (IMM_L(i)) \ + PPC_ORI(d, d, IMM_L(i)); \ } } while(0) + #define PPC_LI64(d, i) do { \ if (!((uintptr_t)(i) & 0xffffffff00000000ULL)) \ PPC_LI32(d, i); \ -- 2.7.4