From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e6.ny.us.ibm.com (e6.ny.us.ibm.com [32.97.182.146]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e1.ny.us.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 11DD067B58 for ; Sat, 19 Aug 2006 04:11:53 +1000 (EST) Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e6.ny.us.ibm.com (8.12.11.20060308/8.12.11) with ESMTP id k7IIBjwM029668 for ; Fri, 18 Aug 2006 14:11:45 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay02.pok.ibm.com (8.13.6/8.13.6/NCO v8.1.1) with ESMTP id k7IIBo3Q240684 for ; Fri, 18 Aug 2006 14:11:50 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id k7IIBn0P029578 for ; Fri, 18 Aug 2006 14:11:50 -0400 Subject: Re: [PATCH] powerpc: emulate power5 popcntb instruction From: Will Schmidt To: Segher Boessenkool In-Reply-To: <36A1A5C6-5269-4BDA-9F3E-A632B3A627DB@kernel.crashing.org> References: <1155840829.9659.16.camel@farscape.rchland.ibm.com> <36A1A5C6-5269-4BDA-9F3E-A632B3A627DB@kernel.crashing.org> Content-Type: text/plain Date: Fri, 18 Aug 2006 13:11:26 -0500 Message-Id: <1155924687.9659.25.camel@farscape.rchland.ibm.com> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Paul Mackerras Reply-To: will_schmidt@vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , In an attempt to make it easier for a power5 optimized app to run on a power4 or a 970 or random earlier machine, this provides emulation of the popcntb instruction. Rewritten to use a slicker algorithm as suggested by Segher. I left a 'tmp' variable in play, as it seemed cleaner to use tmp than referring to regs->gpr[rs] and [ra] multiple times within the magic algorithm. Also tested on power4 with both 32 and 64 userspace this time. *blush*. :-) Signed-off-by: Will Schmidt --- diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 2105767..a0e80dd 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -588,6 +588,8 @@ #define INST_LSWX 0x7c00042a #define INST_STSWI 0x7c0005aa #define INST_STSWX 0x7c00052a +#define INST_POPCNTB 0x7c0000f4 + static int emulate_string_inst(struct pt_regs *regs, u32 instword) { u8 rT = (instword >> 21) & 0x1f; @@ -656,6 +658,23 @@ static int emulate_string_inst(struct pt return 0; } +static int emulate_popcntb_inst(struct pt_regs *regs, u32 instword) +{ + u32 ra,rs; + unsigned long tmp; + + ra = (instword >> 16) & 0x1f; + rs = (instword >> 21) & 0x1f; + + tmp = regs->gpr[rs]; + tmp = tmp - ((tmp >> 1) & 0x5555555555555555); + tmp = (tmp & 0x3333333333333333) + ((tmp >> 2) & 0x3333333333333333); + tmp = (tmp + (tmp >> 4)) & 0x0f0f0f0f0f0f0f0f; + regs->gpr[ra] = tmp; + + return 0; +} + static int emulate_instruction(struct pt_regs *regs) { u32 instword; @@ -693,6 +712,11 @@ static int emulate_instruction(struct pt if ((instword & INST_STRING_GEN_MASK) == INST_STRING) return emulate_string_inst(regs, instword); + /* Emulate the popcntb (Population Count Bytes) instruction. */ + if ((instword & INST_POPCNTB) == INST_POPCNTB) { + return emulate_popcntb_inst(regs, instword); + } + return -EINVAL; }