From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:59037) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TF98i-00084K-GH for qemu-devel@nongnu.org; Fri, 21 Sep 2012 15:43:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TF98g-0002ke-Ri for qemu-devel@nongnu.org; Fri, 21 Sep 2012 15:43:52 -0400 Received: from hall.aurel32.net ([88.191.126.93]:43251) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TF98g-0002jR-KB for qemu-devel@nongnu.org; Fri, 21 Sep 2012 15:43:50 -0400 From: Aurelien Jarno Date: Fri, 21 Sep 2012 21:43:14 +0200 Message-Id: <1348256598-8146-7-git-send-email-aurelien@aurel32.net> In-Reply-To: <1348256598-8146-1-git-send-email-aurelien@aurel32.net> References: <1348256598-8146-1-git-send-email-aurelien@aurel32.net> Subject: [Qemu-devel] [PATCH v2 06/10] tcg/optimize: optimize "op r, a, a => movi r, 0" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Aurelien Jarno Now that it's possible to detect copies, we can optimize the case the "op r, a, a => movi r, 0". This helps in the computation of overflow flags when one of the two args is 0. Reviewed-by: Richard Henderson Signed-off-by: Aurelien Jarno --- tcg/optimize.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/tcg/optimize.c b/tcg/optimize.c index b9a7da9..ceea644 100644 --- a/tcg/optimize.c +++ b/tcg/optimize.c @@ -540,6 +540,22 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr, break; } + /* Simplify expression for "op r, a, a => movi r, 0" cases */ + switch (op) { + CASE_OP_32_64(sub): + CASE_OP_32_64(xor): + if (temps_are_copies(args[1], args[2])) { + gen_opc_buf[op_index] = op_to_movi(op); + tcg_opt_gen_movi(gen_args, args[0], 0); + gen_args += 2; + args += 3; + continue; + } + break; + default: + break; + } + /* Propagate constants through copy operations and do constant folding. Constants will be substituted to arguments by register allocator where needed and possible. Also detect copies. */ -- 1.7.10.4