[PATCH, Loop optimizer]: Add logic to disable certain loop optimizations on pre-/post-loops
Jack Howarth
howarth@bromo.med.uc.edu
Fri Dec 17 16:13:00 GMT 2010
On Fri, Dec 17, 2010 at 01:14:49AM -0600, Fang, Changpeng wrote:
> Hi, Jack:
>
> Thanks for the testing.
>
> This patch is not supposed to slow down a program by 10% (rnflow and test_fpu).
> It would be helpful if you can provide analysis why they are slowed down.
Unfortunately gprof is pretty broken on darwin10 but I can try to do profiling
in Shark with -fno-omit-frame-pointer. Could you try rebenchmarking with the flags...
-ffast-math -funroll-loops -O3 -fPIC -mtune=generic
I'll try benchmarking again with '-Ofast -funroll-loops -mtune=generic' and
see if the performance loss is reduced.
>
> We did see a significant compilation time reduction for most pb05 programs.
> (I don't know why you do not have executable size data).
The sources I have for pb05 aren't fixed for detecting the code size properly
under darwin and I never spent the the time trying to fix that.
>
> >I would note that intel darwin now defaults
> >to -mtune=core2 and always has defaulted to -fPIC.
>
> I could not understand these default for darwin. My understanding is that,
> for x86_64, the default should be -mtune=generic.
This is a recent change.
Author: mrs
Date: Wed Dec 8 23:32:27 2010
New Revision: 167611
URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=167611
Log:
2010-12-08 Iain Sandoe <iains@gcc.gnu.org>
gcc/config.gcc (with_cpu): Default i[34567]86-*-darwin* and
x86_64-*-darwin* to with_cpu:-core2.
gcc/config/i386/mmx.md (*mov<mode>_internal_rex64): Replace movq
with movd for darwin assembler.
gcc/config/i386/sse.md (*vec_concatv2di_rex64_sse4_1): Ditto.
(*vec_concatv2di_rex64_sse): Ditto.
Modified:
trunk/gcc/ChangeLog
trunk/gcc/config.gcc
trunk/gcc/config/i386/mmx.md
trunk/gcc/config/i386/sse.md
We had intended to do this awhile back (since all darwin hardware is core2
or recent Xeon), but held off until the core2 costs tables were improved to
match those of generic.
http://gcc.gnu.org/ml/gcc-patches/2010-12/msg00000.html
>
> Thanks,
>
> Changpeng
>
> ________________________________________
> From: Jack Howarth [howarth@bromo.med.uc.edu]
> Sent: Thursday, December 16, 2010 11:31 PM
> To: Fang, Changpeng
> Cc: Zdenek Dvorak; Richard Guenther; Xinliang David Li; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH, Loop optimizer]: Add logic to disable certain loop optimizations on pre-/post-loops
>
> On Thu, Dec 16, 2010 at 06:13:52PM -0600, Fang, Changpeng wrote:
> > Hi,
> >
> > Based on previous discussions, I modified the patch as such.
> >
> > If a loop is marked as non-rolling, optimize_loop_for_size_p returns TRUE
> > and optimize_loop_for_speed_p returns FALSE. All users of these two
> > functions will be affected.
> >
> > After applying the modified patch, pb05 compilation time decreases 29%, binary
> > size decreases 20%, while a small (0.5%) performance increase was found which may
> > be just noise.
> >
> > Modified patch passed bootstrapping and gcc regression tests on x86_64-unknown-linux-gnu.
> >
> > Is it OK to commit to trunk?
>
> Changpeng,
> On x86_64-apple-darwin10, I am finding a more severe penalty for this patch with
> the pb05 benchmarks. Using a profiledbootstrap BOOT_CFLAGS="-g -O3" build with...
>
> Configured with: ../gcc-4.6-20101216/configure --prefix=/sw --prefix=/sw/lib/gcc4.6 --mandir=/sw/share/man --infodir=/sw/lib/gcc4.6/info --enable-languages=c,c++,fortran,objc,obj-c++,java --with-gmp=/sw --with-libiconv-prefix=/sw --with-ppl=/sw --with-cloog=/sw --with-mpc=/sw --with-system-zlib --x-includes=/usr/X11R6/include --x-libraries=/usr/X11R6/lib --program-suffix=-fsf-4.6 --enable-checking=yes --enable-cloog-backend=isl --enable-build-with-cxx
>
> I get without the patch...
>
> ================================================================================
> Date & Time : 16 Dec 2010 23:36:27
> Test Name : gfortran_lin_O3
> Compile Command : gfortran -ffast-math -funroll-loops -O3 %n.f90 -o %n
> Benchmarks : ac aermod air capacita channel doduc fatigue gas_dyn induct linpk mdbx nf protein rnflow test_fpu tfft
> Maximum Times : 2000.0
> Target Error % : 0.100
> Minimum Repeats : 10
> Maximum Repeats : 100
>
> Benchmark Compile Executable Ave Run Number Estim
> Name (secs) (bytes) (secs) Repeats Err %
> --------- ------- ---------- ------- ------- ------
> ac 1.76 10000 8.78 12 0.0081
> aermod 54.94 10000 17.28 10 0.0307
> air 3.44 10000 5.53 13 0.0734
> capacita 2.64 10000 32.65 10 0.0096
> channel 0.89 10000 1.84 20 0.0977
> doduc 8.12 10000 27.00 10 0.0132
> fatigue 3.06 10000 8.36 10 0.0104
> gas_dyn 5.00 10000 4.30 17 0.0915
> induct 6.24 10000 12.42 10 0.0100
> linpk 1.02 10000 15.50 12 0.0542
> mdbx 2.55 10000 11.24 10 0.0256
> nf 2.90 10000 30.16 20 0.0989
> protein 7.98 10000 33.72 10 0.0070
> rnflow 9.34 10000 23.21 10 0.0551
> test_fpu 6.72 10000 8.05 10 0.0426
> tfft 0.76 10000 1.87 10 0.0597
>
> Geometric Mean Execution Time = 10.87 seconds
>
> and with the patch...
>
> ================================================================================
> Date & Time : 16 Dec 2010 21:31:06
> Test Name : gfortran_lin_O3
> Compile Command : gfortran -ffast-math -funroll-loops -O3 %n.f90 -o %n
> Benchmarks : ac aermod air capacita channel doduc fatigue gas_dyn induct linpk mdbx nf protein rnflow test_fpu tfft
> Maximum Times : 2000.0
> Target Error % : 0.100
> Minimum Repeats : 10
> Maximum Repeats : 100
>
> Benchmark Compile Executable Ave Run Number Estim
> Name (secs) (bytes) (secs) Repeats Err %
> --------- ------- ---------- ------- ------- ------
> ac 1.19 10000 8.78 10 0.0099
> aermod 47.91 10000 16.95 10 0.0123
> air 2.85 10000 5.34 12 0.0715
> capacita 1.63 10000 33.10 10 0.0361
> channel 0.67 10000 1.87 10 0.0884
> doduc 6.42 10000 27.35 10 0.0206
> fatigue 2.10 10000 8.32 10 0.0194
> gas_dyn 2.07 10000 4.30 17 0.0843
> induct 5.38 10000 12.58 10 0.0088
> linpk 0.71 10000 15.69 18 0.0796
> mdbx 1.95 10000 11.41 10 0.0238
> nf 1.24 10000 31.34 12 0.0991
> protein 3.88 10000 35.13 10 0.0659
> rnflow 4.73 10000 25.97 10 0.0629
> test_fpu 3.66 10000 8.88 11 0.0989
> tfft 0.52 10000 1.89 10 0.0403
>
> Geometric Mean Execution Time = 11.09 seconds
>
> This shows about a 2.0% performance reduction in the Geometric
> Mean Execution Time. I would note that intel darwin now defaults
> to -mtune=core2 and always has defaulted to -fPIC.
> Jack
>
> >
> > Thanks,
> >
> > Changpeng
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > ________________________________________
> > From: Zdenek Dvorak [rakdver@kam.mff.cuni.cz]
> > Sent: Thursday, December 16, 2010 12:47 PM
> > To: Fang, Changpeng
> > Cc: Richard Guenther; Xinliang David Li; gcc-patches@gcc.gnu.org
> > Subject: Re: [PATCH, Loop optimizer]: Add logic to disable certain loop optimizations on pre-/post-loops
> >
> > Hi,
> >
> > > For prefetching of prologue or epilogue loops, we have two choices (1) prefetching not
> > > not unrolling, (2) not prefetching. Which one do you prefer?
> >
> > it is better not to prefetch (the current placement of prefetches is not good for non-rolling
> > loops),
> >
> > Zdenek
> >
>
> Content-Description: polyhedron1.txt
> > Comparison of Polyhedron (2005) Compile Time, Binary Size and Performance After Applying the NON-ROLLING Marking Patch
> >
> > gfortran -Ofast -funroll-loops -march=amdfam10 %n.f90 -o %n
> > ============================================================================================================================
> > || | Before Patch | After Patch | Changes ||
> > ||========================================================================================================================||
> > || Benchmark | Compile Binary Size Run Time | Compile Binary Size Run Time | Compile Binary Performance ||
> > || Name | Time (s) (bytes) (s) | Time(s) (bytes) (secs) | Time (%) Size(%) (%) ||
> > ||========================================================================================================================||
> > || ac | 3.36 41976 13.26 | 2.52 34424 13.21 | -25.00 -17.99 0.38 ||
> > || aermod | 103.45 1412221 44.36 | 86.55 1268861 43.08 | -16.34 -10.15 2.97 ||
> > || air | 6.11 75186 11.73 | 5.72 71090 11.56 | -6.38 -5.45 1.47 ||
> > || capacita | 6.83 91257 88.40 | 4.70 74585 88.01 | -31.19 -18.27 0.44 ||
> > || channel | 2.14 39984 6.65 | 1.84 35888 6.69 | -14.02 -10.24 -0.60 ||
> > || doduc | 12.78 198624 38.59 | 12.20 186336 38.18 | -4.54 -6.19 1.07 ||
> > || fatigue | 9.11 110008 10.15 | 5.93 92472 10.12 | -34.91 -15.94 0.30 ||
> > || gas_dyn | 15.69 149726 7.14 | 8.45 109342 6.96 | -46.14 -26.97 2.59 ||
> > || induct | 10.98 191800 20.66 | 10.62 188168 20.61 | -3.28 -1.89 0.24 ||
> > || linpk | 2.27 46073 19.03 | 1.68 33401 19.03 | -25.99 -27.50 0.00 ||
> > || mdbx | 5.63 103731 21.41 | 4.24 83251 21.33 | -24.69 -19.74 0.38 ||
> > || nf | 14.18 118451 22.88 | 5.55 60499 23.14 | -60.86 -48.92 -1.12 ||
> > || protein | 34.20 177700 47.04 | 19.16 135012 46.94 | -43.98 -24.02 0.21 ||
> > || rnflow | 42.13 283645 40.30 | 20.92 178477 40.65 | -50.34 -37.08 -0.86 ||
> > || test_fpu | 30.17 252080 14.46 | 14.44 149136 14.32 | -52.14 -40.84 0.98 ||
> > || tfft | 1.50 32450 7.71 | 1.12 26546 7.67 | -25.33 -18.19 0.52 ||
> > ||========================================================================================================================||
> > || average | 19.57 | 19.46 | -29.07 -20.59 0.56 ||
> > ============================================================================================================================
>
> Content-Description: 0001-Don-t-perform-certain-loop-optimizations-on-pre-post.patch
> > From cd8b85bba1b39e108235f44d9d07918179ff3d79 Mon Sep 17 00:00:00 2001
> > From: Changpeng Fang <chfang@houghton.(none)>
> > Date: Mon, 13 Dec 2010 12:01:49 -0800
> > Subject: [PATCH] Don't perform certain loop optimizations on pre/post loops
> >
> > * basic-block.h (bb_flags): Add a new flag BB_HEADER_OF_NONROLLING_LOOP.
> > * cfg.c (clear_bb_flags): Keep BB_HEADER_OF_NONROLLING marker.
> > * cfgloop.h (mark_non_rolling_loop): New function declaration.
> > (non_rolling_loop_p): New function declaration.
> > * predict.c (optimize_loop_for_size_p): Return true if the loop was marked
> > NON-ROLLING. (optimize_loop_for_speed_p): Return false if the loop was
> > marked NON-ROLLING.
> > * tree-ssa-loop-manip.c (tree_transform_and_unroll_loop): Mark the
> > non-rolling loop.
> > * tree-ssa-loop-niter.c (mark_non_rolling_loop): Implement the new
> > function. (non_rolling_loop_p): Implement the new function.
> > * tree-vect-loop-manip.c (vect_do_peeling_for_loop_bound): Mark the
> > non-rolling loop. (vect_do_peeling_for_alignment): Mark the non-rolling
> > loop.
> > ---
> > gcc/basic-block.h | 6 +++++-
> > gcc/cfg.c | 7 ++++---
> > gcc/cfgloop.h | 2 ++
> > gcc/predict.c | 6 ++++++
> > gcc/tree-ssa-loop-manip.c | 3 +++
> > gcc/tree-ssa-loop-niter.c | 20 ++++++++++++++++++++
> > gcc/tree-vect-loop-manip.c | 8 ++++++++
> > 7 files changed, 48 insertions(+), 4 deletions(-)
> >
> > diff --git a/gcc/basic-block.h b/gcc/basic-block.h
> > index be0a1d1..850472d 100644
> > --- a/gcc/basic-block.h
> > +++ b/gcc/basic-block.h
> > @@ -245,7 +245,11 @@ enum bb_flags
> >
> > /* Set on blocks that cannot be threaded through.
> > Only used in cfgcleanup.c. */
> > - BB_NONTHREADABLE_BLOCK = 1 << 11
> > + BB_NONTHREADABLE_BLOCK = 1 << 11,
> > +
> > + /* Set on blocks that are headers of non-rolling loops. */
> > + BB_HEADER_OF_NONROLLING_LOOP = 1 << 12
> > +
> > };
> >
> > /* Dummy flag for convenience in the hot/cold partitioning code. */
> > diff --git a/gcc/cfg.c b/gcc/cfg.c
> > index c8ef799..e59a637 100644
> > --- a/gcc/cfg.c
> > +++ b/gcc/cfg.c
> > @@ -425,8 +425,8 @@ redirect_edge_pred (edge e, basic_block new_pred)
> > connect_src (e);
> > }
> >
> > -/* Clear all basic block flags, with the exception of partitioning and
> > - setjmp_target. */
> > +/* Clear all basic block flags, with the exception of partitioning,
> > + setjmp_target, and the non-rolling loop marker. */
> > void
> > clear_bb_flags (void)
> > {
> > @@ -434,7 +434,8 @@ clear_bb_flags (void)
> >
> > FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
> > bb->flags = (BB_PARTITION (bb)
> > - | (bb->flags & (BB_DISABLE_SCHEDULE + BB_RTL + BB_NON_LOCAL_GOTO_TARGET)));
> > + | (bb->flags & (BB_DISABLE_SCHEDULE + BB_RTL + BB_NON_LOCAL_GOTO_TARGET
> > + + BB_HEADER_OF_NONROLLING_LOOP)));
> > }
> >
> > /* Check the consistency of profile information. We can't do that
> > diff --git a/gcc/cfgloop.h b/gcc/cfgloop.h
> > index bf2614e..e856a78 100644
> > --- a/gcc/cfgloop.h
> > +++ b/gcc/cfgloop.h
> > @@ -279,6 +279,8 @@ extern rtx doloop_condition_get (rtx);
> > void estimate_numbers_of_iterations_loop (struct loop *, bool);
> > HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
> > bool estimated_loop_iterations (struct loop *, bool, double_int *);
> > +void mark_non_rolling_loop (struct loop *);
> > +bool non_rolling_loop_p (struct loop *);
> >
> > /* Loop manipulation. */
> > extern bool can_duplicate_loop_p (const struct loop *loop);
> > diff --git a/gcc/predict.c b/gcc/predict.c
> > index c691990..bf729f8 100644
> > --- a/gcc/predict.c
> > +++ b/gcc/predict.c
> > @@ -279,6 +279,9 @@ optimize_insn_for_speed_p (void)
> > bool
> > optimize_loop_for_size_p (struct loop *loop)
> > {
> > + /* Loops marked NON-ROLLING are not likely to be hot. */
> > + if (non_rolling_loop_p (loop))
> > + return true;
> > return optimize_bb_for_size_p (loop->header);
> > }
> >
> > @@ -287,6 +290,9 @@ optimize_loop_for_size_p (struct loop *loop)
> > bool
> > optimize_loop_for_speed_p (struct loop *loop)
> > {
> > + /* Loops marked NON-ROLLING are not likely to be hot. */
> > + if (non_rolling_loop_p (loop))
> > + return false;
> > return optimize_bb_for_speed_p (loop->header);
> > }
> >
> > diff --git a/gcc/tree-ssa-loop-manip.c b/gcc/tree-ssa-loop-manip.c
> > index 87b2c0d..bc977bb 100644
> > --- a/gcc/tree-ssa-loop-manip.c
> > +++ b/gcc/tree-ssa-loop-manip.c
> > @@ -931,6 +931,9 @@ tree_transform_and_unroll_loop (struct loop *loop, unsigned factor,
> > gcc_assert (new_loop != NULL);
> > update_ssa (TODO_update_ssa);
> >
> > + /* NEW_LOOP is a non-rolling loop. */
> > + mark_non_rolling_loop (new_loop);
> > +
> > /* Determine the probability of the exit edge of the unrolled loop. */
> > new_est_niter = est_niter / factor;
> >
> > diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
> > index ee85f6f..1e2e4b2 100644
> > --- a/gcc/tree-ssa-loop-niter.c
> > +++ b/gcc/tree-ssa-loop-niter.c
> > @@ -3011,6 +3011,26 @@ estimate_numbers_of_iterations (bool use_undefined_p)
> > fold_undefer_and_ignore_overflow_warnings ();
> > }
> >
> > +/* Mark LOOP as a non-rolling loop. */
> > +
> > +void
> > +mark_non_rolling_loop (struct loop *loop)
> > +{
> > + gcc_assert (loop && loop->header);
> > + loop->header->flags |= BB_HEADER_OF_NONROLLING_LOOP;
> > +}
> > +
> > +/* Return true if LOOP is a non-rolling loop. */
> > +
> > +bool
> > +non_rolling_loop_p (struct loop *loop)
> > +{
> > + int masked_flags;
> > + gcc_assert (loop && loop->header);
> > + masked_flags = (loop->header->flags & BB_HEADER_OF_NONROLLING_LOOP);
> > + return (masked_flags != 0);
> > +}
> > +
> > /* Returns true if statement S1 dominates statement S2. */
> >
> > bool
> > diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
> > index 6ecd304..216de78 100644
> > --- a/gcc/tree-vect-loop-manip.c
> > +++ b/gcc/tree-vect-loop-manip.c
> > @@ -1938,6 +1938,10 @@ vect_do_peeling_for_loop_bound (loop_vec_info loop_vinfo, tree *ratio,
> > cond_expr, cond_expr_stmt_list);
> > gcc_assert (new_loop);
> > gcc_assert (loop_num == loop->num);
> > +
> > + /* NEW_LOOP is a non-rolling loop. */
> > + mark_non_rolling_loop (new_loop);
> > +
> > #ifdef ENABLE_CHECKING
> > slpeel_verify_cfg_after_peeling (loop, new_loop);
> > #endif
> > @@ -2191,6 +2195,10 @@ vect_do_peeling_for_alignment (loop_vec_info loop_vinfo)
> > th, true, NULL_TREE, NULL);
> >
> > gcc_assert (new_loop);
> > +
> > + /* NEW_LOOP is a non-rolling loop. */
> > + mark_non_rolling_loop (new_loop);
> > +
> > #ifdef ENABLE_CHECKING
> > slpeel_verify_cfg_after_peeling (new_loop, loop);
> > #endif
> > --
> > 1.6.3.3
> >
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