From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 7075 invoked by alias); 20 Apr 2014 06:37:54 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 7066 invoked by uid 89); 20 Apr 2014 06:37:53 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.1 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: atrey.karlin.mff.cuni.cz Received: from atrey.karlin.mff.cuni.cz (HELO atrey.karlin.mff.cuni.cz) (195.113.26.193) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sun, 20 Apr 2014 06:37:51 +0000 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 4018) id 0C637819CB; Sun, 20 Apr 2014 08:37:48 +0200 (CEST) Date: Sun, 20 Apr 2014 07:09:00 -0000 From: Jan Hubicka To: Richard Biener Cc: gcc-patches@gcc.gnu.org Subject: Re: [PATCH][RFC] Remove RTL loop unswitching Message-ID: <20140420063748.GB23141@atrey.karlin.mff.cuni.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) X-IsSubscribed: yes X-SW-Source: 2014-04/txt/msg01136.txt.bz2 > > This removes RTL loop unswitching (see last years discussion about > compile-time issues of that pass). RTL loop unswitching is > enabled together with GIMPLE loop unswitching at -O3 and by > -floop-unswitch. It's clearly the wrong place to do high-level > loop transforms these days, and the cost of maintainance doesn't > outweight the questionable benefit. > > Thus the following patch removes it. > > Bootstrap / regtest pending on x86_64-unknown-linux-gnu (I hope > for testsuite fallout). > > Any objections? Not really, I am all for moving more of loop stuff to trees. Did you performed some benchmarks? (I remember I did in 2012 but completely forgot the outcome). On related note, shall I try to update the following? http://gcc.gnu.org/ml/gcc-patches/2013-11/msg02270.html Honza > > Thanks, > Richard. > > 2014-04-15 Richard Biener > > * Makefile.in (OBJS): Remove loop-unswitch.o. > * loop-unswitch.c: Delete. > * tree-pass.h (make_pass_rtl_unswitch): Remove. > * passes.def (pass_rtl_unswitch): Likewise. > * loop-init.c (gate_rtl_unswitch): Likewise. > (rtl_unswitch): Likewise. > (pass_data_rtl_unswitch): Likewise. > (pass_rtl_unswitch): Likewise. > (make_pass_rtl_unswitch): Likewise. > * rtl.h (reversed_condition): Likewise. > (compare_and_jump_seq): Likewise. > * loop-iv.c (reversed_condition): Move here from loop-unswitch.c > and make static. > * loop-unroll.c (compare_and_jump_seq): Likewise. > > Index: gcc/Makefile.in > =================================================================== > --- gcc/Makefile.in (revision 209410) > +++ gcc/Makefile.in (working copy) > @@ -1294,7 +1294,6 @@ OBJS = \ > loop-invariant.o \ > loop-iv.o \ > loop-unroll.o \ > - loop-unswitch.o \ > lower-subreg.o \ > lra.o \ > lra-assigns.o \ > Index: gcc/tree-pass.h > =================================================================== > --- gcc/tree-pass.h (revision 209410) > +++ gcc/tree-pass.h (working copy) > @@ -512,7 +512,6 @@ extern rtl_opt_pass *make_pass_outof_cfg > extern rtl_opt_pass *make_pass_loop2 (gcc::context *ctxt); > extern rtl_opt_pass *make_pass_rtl_loop_init (gcc::context *ctxt); > extern rtl_opt_pass *make_pass_rtl_move_loop_invariants (gcc::context *ctxt); > -extern rtl_opt_pass *make_pass_rtl_unswitch (gcc::context *ctxt); > extern rtl_opt_pass *make_pass_rtl_unroll_and_peel_loops (gcc::context *ctxt); > extern rtl_opt_pass *make_pass_rtl_doloop (gcc::context *ctxt); > extern rtl_opt_pass *make_pass_rtl_loop_done (gcc::context *ctxt); > Index: gcc/passes.def > =================================================================== > --- gcc/passes.def (revision 209410) > +++ gcc/passes.def (working copy) > @@ -341,7 +341,6 @@ along with GCC; see the file COPYING3. > PUSH_INSERT_PASSES_WITHIN (pass_loop2) > NEXT_PASS (pass_rtl_loop_init); > NEXT_PASS (pass_rtl_move_loop_invariants); > - NEXT_PASS (pass_rtl_unswitch); > NEXT_PASS (pass_rtl_unroll_and_peel_loops); > NEXT_PASS (pass_rtl_doloop); > NEXT_PASS (pass_rtl_loop_done); > Index: gcc/loop-init.c > =================================================================== > --- gcc/loop-init.c (revision 209410) > +++ gcc/loop-init.c (working copy) > @@ -518,61 +518,7 @@ make_pass_rtl_move_loop_invariants (gcc: > } > > > -/* Loop unswitching for RTL. */ > -static bool > -gate_rtl_unswitch (void) > -{ > - return flag_unswitch_loops; > -} > - > -static unsigned int > -rtl_unswitch (void) > -{ > - if (number_of_loops (cfun) > 1) > - unswitch_loops (); > - return 0; > -} > - > -namespace { > - > -const pass_data pass_data_rtl_unswitch = > -{ > - RTL_PASS, /* type */ > - "loop2_unswitch", /* name */ > - OPTGROUP_LOOP, /* optinfo_flags */ > - true, /* has_gate */ > - true, /* has_execute */ > - TV_LOOP_UNSWITCH, /* tv_id */ > - 0, /* properties_required */ > - 0, /* properties_provided */ > - 0, /* properties_destroyed */ > - 0, /* todo_flags_start */ > - TODO_verify_rtl_sharing, /* todo_flags_finish */ > -}; > - > -class pass_rtl_unswitch : public rtl_opt_pass > -{ > -public: > - pass_rtl_unswitch (gcc::context *ctxt) > - : rtl_opt_pass (pass_data_rtl_unswitch, ctxt) > - {} > - > - /* opt_pass methods: */ > - bool gate () { return gate_rtl_unswitch (); } > - unsigned int execute () { return rtl_unswitch (); } > - > -}; // class pass_rtl_unswitch > - > -} // anon namespace > - > -rtl_opt_pass * > -make_pass_rtl_unswitch (gcc::context *ctxt) > -{ > - return new pass_rtl_unswitch (ctxt); > -} > - > - > -/* Loop unswitching for RTL. */ > +/* Loop unrolling and peeling for RTL. */ > static bool > gate_rtl_unroll_and_peel_loops (void) > { > Index: gcc/loop-iv.c > =================================================================== > --- gcc/loop-iv.c (revision 209410) > +++ gcc/loop-iv.c (working copy) > @@ -1732,6 +1732,21 @@ canon_condition (rtx cond) > return cond; > } > > +/* Reverses CONDition; returns NULL if we cannot. */ > + > +static rtx > +reversed_condition (rtx cond) > +{ > + enum rtx_code reversed; > + reversed = reversed_comparison_code (cond, NULL); > + if (reversed == UNKNOWN) > + return NULL_RTX; > + else > + return gen_rtx_fmt_ee (reversed, > + GET_MODE (cond), XEXP (cond, 0), > + XEXP (cond, 1)); > +} > + > /* Tries to use the fact that COND holds to simplify EXPR. ALTERED is the > set of altered regs. */ > > Index: gcc/loop-unroll.c > =================================================================== > --- gcc/loop-unroll.c (revision 209410) > +++ gcc/loop-unroll.c (working copy) > @@ -1060,6 +1060,59 @@ split_edge_and_insert (edge e, rtx insns > return bb; > } > > +/* Prepare a sequence comparing OP0 with OP1 using COMP and jumping to LABEL if > + true, with probability PROB. If CINSN is not NULL, it is the insn to copy > + in order to create a jump. */ > + > +static rtx > +compare_and_jump_seq (rtx op0, rtx op1, enum rtx_code comp, rtx label, int prob, > + rtx cinsn) > +{ > + rtx seq, jump, cond; > + enum machine_mode mode; > + > + mode = GET_MODE (op0); > + if (mode == VOIDmode) > + mode = GET_MODE (op1); > + > + start_sequence (); > + if (GET_MODE_CLASS (mode) == MODE_CC) > + { > + /* A hack -- there seems to be no easy generic way how to make a > + conditional jump from a ccmode comparison. */ > + gcc_assert (cinsn); > + cond = XEXP (SET_SRC (pc_set (cinsn)), 0); > + gcc_assert (GET_CODE (cond) == comp); > + gcc_assert (rtx_equal_p (op0, XEXP (cond, 0))); > + gcc_assert (rtx_equal_p (op1, XEXP (cond, 1))); > + emit_jump_insn (copy_insn (PATTERN (cinsn))); > + jump = get_last_insn (); > + gcc_assert (JUMP_P (jump)); > + JUMP_LABEL (jump) = JUMP_LABEL (cinsn); > + LABEL_NUSES (JUMP_LABEL (jump))++; > + redirect_jump (jump, label, 0); > + } > + else > + { > + gcc_assert (!cinsn); > + > + op0 = force_operand (op0, NULL_RTX); > + op1 = force_operand (op1, NULL_RTX); > + do_compare_rtx_and_jump (op0, op1, comp, 0, > + mode, NULL_RTX, NULL_RTX, label, -1); > + jump = get_last_insn (); > + gcc_assert (JUMP_P (jump)); > + JUMP_LABEL (jump) = label; > + LABEL_NUSES (label)++; > + } > + add_int_reg_note (jump, REG_BR_PROB, prob); > + > + seq = get_insns (); > + end_sequence (); > + > + return seq; > +} > + > /* Unroll LOOP for which we are able to count number of iterations in runtime > LOOP->LPT_DECISION.TIMES times. The transformation does this (with some > extra care for case n < 0): > Index: gcc/rtl.h > =================================================================== > --- gcc/rtl.h (revision 209410) > +++ gcc/rtl.h (working copy) > @@ -2743,10 +2743,6 @@ extern unsigned int variable_tracking_ma > extern void get_mode_bounds (enum machine_mode, int, enum machine_mode, > rtx *, rtx *); > > -/* In loop-unswitch.c */ > -extern rtx reversed_condition (rtx); > -extern rtx compare_and_jump_seq (rtx, rtx, enum rtx_code, rtx, int, rtx); > - > /* In loop-iv.c */ > extern rtx canon_condition (rtx); > extern void simplify_using_condition (rtx, rtx *, bitmap);