From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50530) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dPmMO-0003DQ-EE for qemu-devel@nongnu.org; Tue, 27 Jun 2017 05:00:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dPmMJ-00011b-RQ for qemu-devel@nongnu.org; Tue, 27 Jun 2017 05:00:36 -0400 Received: from mail-wr0-x230.google.com ([2a00:1450:400c:c0c::230]:36530) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dPmMJ-00010n-L5 for qemu-devel@nongnu.org; Tue, 27 Jun 2017 05:00:31 -0400 Received: by mail-wr0-x230.google.com with SMTP id c11so155787630wrc.3 for ; Tue, 27 Jun 2017 02:00:31 -0700 (PDT) References: <20170621024831.26019-1-rth@twiddle.net> <20170621024831.26019-11-rth@twiddle.net> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <20170621024831.26019-11-rth@twiddle.net> Date: Tue, 27 Jun 2017 10:01:21 +0100 Message-ID: <87tw31x0ri.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH 10/16] tcg: Avoid loops against variable bounds List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: qemu-devel@nongnu.org, aurelien@aurel32.net Richard Henderson writes: > Copy s->nb_globals or s->nb_temps to a local variable for the purposes > of iteration. This should allow the compiler to use low-overhead > looping constructs on some hosts. > > Signed-off-by: Richard Henderson > --- > tcg/tcg.c | 27 ++++++++++----------------- > 1 file changed, 10 insertions(+), 17 deletions(-) > > diff --git a/tcg/tcg.c b/tcg/tcg.c > index e78140b..c228f1e 100644 > --- a/tcg/tcg.c > +++ b/tcg/tcg.c > @@ -943,23 +943,16 @@ void tcg_gen_callN(TCGContext *s, void *func, TCGArg ret, > > static void tcg_reg_alloc_start(TCGContext *s) > { > - int i; > + int i, n; > TCGTemp *ts; > - for(i = 0; i < s->nb_globals; i++) { > + > + for (i = 0, n = s->nb_globals; i < n; i++) { > ts = &s->temps[i]; > - if (ts->fixed_reg) { > - ts->val_type = TEMP_VAL_REG; > - } else { > - ts->val_type = TEMP_VAL_MEM; > - } > + ts->val_type = (ts->fixed_reg ? TEMP_VAL_REG : TEMP_VAL_MEM); > } > - for(i = s->nb_globals; i < s->nb_temps; i++) { > + for (n = s->nb_temps; i < n; i++) { A one line comment like /* i continues on from s->nb_globals above */ might prevent a momentary confusion when reading through. > ts = &s->temps[i]; > - if (ts->temp_local) { > - ts->val_type = TEMP_VAL_MEM; > - } else { > - ts->val_type = TEMP_VAL_DEAD; > - } > + ts->val_type = (ts->temp_local ? TEMP_VAL_MEM : TEMP_VAL_DEAD); > ts->mem_allocated = 0; > ts->fixed_reg = 0; > } > @@ -2050,9 +2043,9 @@ static void temp_save(TCGContext *s, TCGTemp *ts, TCGRegSet allocated_regs) > temporary registers needs to be allocated to store a constant. */ > static void save_globals(TCGContext *s, TCGRegSet allocated_regs) > { > - int i; > + int i, n; > > - for (i = 0; i < s->nb_globals; i++) { > + for (i = 0, n = s->nb_globals; i < n; i++) { > temp_save(s, &s->temps[i], allocated_regs); > } > } > @@ -2062,9 +2055,9 @@ static void save_globals(TCGContext *s, TCGRegSet allocated_regs) > temporary registers needs to be allocated to store a constant. */ > static void sync_globals(TCGContext *s, TCGRegSet allocated_regs) > { > - int i; > + int i, n; > > - for (i = 0; i < s->nb_globals; i++) { > + for (i = 0, n = s->nb_globals; i < n; i++) { > TCGTemp *ts = &s->temps[i]; > tcg_debug_assert(ts->val_type != TEMP_VAL_REG > || ts->fixed_reg Otherwise: Reviewed-by: Alex Bennée -- Alex Bennée