[Bug tree-optimization/46928] data dependence analysis fails on constant array accesses

[spop at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46928

Sebastian Pop  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution||FIXED

--- Comment #7 from Sebastian Pop  2010-12-15 05:07:27 
UTC ---
Fixed.

[Bug tree-optimization/46928] data dependence analysis fails on constant array accesses

[spop at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46928

--- Comment #6 from Sebastian Pop  2010-12-15 05:04:43 
UTC ---
Author: spop
Date: Wed Dec 15 05:04:40 2010
New Revision: 167843

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=167843
Log:
Fix PR46928: handle "A[p] == A[p]" in data dep analysis with p a parameter of
the loop.

2010-12-14  Sebastian Pop  

PR tree-optimization/46928
* tree-data-ref.c (analyze_overlapping_iterations): Handle "A[p] == A[p]"
in data dependence analysis with p a parameter of the loop.

* gcc.dg/tree-ssa/ldist-17.c: New.

Added:
trunk/gcc/testsuite/gcc.dg/tree-ssa/ldist-17.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-data-ref.c

[Bug tree-optimization/46928] data dependence analysis fails on constant array accesses

[spop at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46928

--- Comment #5 from Sebastian Pop  2010-12-13 19:30:19 
UTC ---
The code from comment #4 comes from 
./cc1 -O2 -ftree-loop-distribution -fdump-tree-ldist-details
as on -O3 we end up unrolling all the loops.

[Bug tree-optimization/46928] data dependence analysis fails on constant array accesses

[sebpop at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46928

--- Comment #4 from sebpop at gmail dot com  
2010-12-13 19:05:58 UTC ---
The code that is produced looks like this just after loop
distribution, i.e., we generate memset zero only by distributing the
innermost loop:

mad_synth_mute (struct mad_synth * synth)
{
  long unsigned int D.2739;
  long unsigned int D.2740;
  long unsigned int D.2741;
  long unsigned int D.2742;
  long unsigned int D.2743;
  struct mad_synth * D.2744;
  long unsigned int D.2730;
  long unsigned int D.2731;
  long unsigned int D.2732;
  long unsigned int D.2733;
   D.2734;
   D.2735;
   D.2736;
  long unsigned int D.2737;
  struct mad_synth * D.2738;
  long unsigned int D.2721;
  long unsigned int D.2722;
  long unsigned int D.2723;
  long unsigned int D.2724;
   D.2725;
   D.2726;
   D.2727;
  long unsigned int D.2728;
  struct mad_synth * D.2729;
  long unsigned int D.2712;
  long unsigned int D.2713;
  long unsigned int D.2714;
  long unsigned int D.2715;
   D.2716;
   D.2717;
   D.2718;
  long unsigned int D.2719;
  struct mad_synth * D.2720;
  unsigned int pretmp.2;
  unsigned int v;
  unsigned int s;
  unsigned int ch;

:
  goto ;

:
Invalid sum of incoming frequencies 139, should be 
  s_9 = s_29 + 1;
  if (s_9 != 16)
goto ;
  else
goto ;

:

:
Invalid sum of outgoing probabilities 12.5%
  # s_29 = PHI <0(10), s_9(6)>
  D.2712_25 = (long unsigned int) s_29;
  D.2713_22 = (long unsigned int) ch_28;
  D.2714_1 = D.2713_22 * 64;
  D.2715_2 = D.2712_25 + D.2714_1;
  D.2716_3 = () D.2715_2;
  D.2717_26 = D.2716_3 + 48;
  D.2718_27 = D.2717_26 * 32;
  D.2719_24 = (long unsigned int) D.2718_27;
  D.2720_23 = synth_7(D) + D.2719_24;
  __builtin_memset (D.2720_23, 0, 32);
  D.2721_13 = (long unsigned int) s_29;
  D.2722_12 = (long unsigned int) ch_28;
  D.2723_11 = D.2722_12 * 64;
  D.2724_6 = D.2721_13 + D.2723_11;
  D.2725_20 = () D.2724_6;
  D.2726_32 = D.2725_20 + 32;
  D.2727_33 = D.2726_32 * 32;
  D.2728_34 = (long unsigned int) D.2727_33;
  D.2729_35 = synth_7(D) + D.2728_34;
  __builtin_memset (D.2729_35, 0, 32);
  D.2730_36 = (long unsigned int) s_29;
  D.2731_37 = (long unsigned int) ch_28;
  D.2732_38 = D.2731_37 * 64;
  D.2733_39 = D.2730_36 + D.2732_38;
  D.2734_40 = () D.2733_39;
  D.2735_41 = D.2734_40 + 16;
  D.2736_42 = D.2735_41 * 32;
  D.2737_43 = (long unsigned int) D.2736_42;
  D.2738_44 = synth_7(D) + D.2737_43;
  __builtin_memset (D.2738_44, 0, 32);
  D.2739_45 = (long unsigned int) ch_28;
  D.2740_46 = D.2739_45 * 64;
  D.2741_47 = (long unsigned int) s_29;
  D.2742_48 = D.2740_46 + D.2741_47;
  D.2743_49 = D.2742_48 * 32;
  D.2744_50 = synth_7(D) + D.2743_49;
  __builtin_memset (D.2744_50, 0, 32);
  goto ;

:
  ch_10 = ch_28 + 1;
  if (ch_10 != 2)
goto ;
  else
goto ;

:

:
  # ch_28 = PHI <0(2), ch_10(9)>
  goto ;

:
  return;

}

and the assembler:

mad_synth_mute:
.LFB0:
.cfi_startproc
movq%rdi, %r9
xorl%r8d, %r8d
.L2:
leaq16(%r8), %rsi
movq%r9, %rdx
movq%r8, %rax
.p2align 4,,10
.p2align 3
.L3:
leaq48(%rax), %rcx
salq$5, %rcx
addq%rdi, %rcx
movq$0, (%rcx)
movq$0, 8(%rcx)
movq$0, 16(%rcx)
movq$0, 24(%rcx)
leaq32(%rax), %rcx
salq$5, %rcx
addq%rdi, %rcx
movq$0, (%rcx)
movq$0, 8(%rcx)
movq$0, 16(%rcx)
movq$0, 24(%rcx)
leaq16(%rax), %rcx
addq$1, %rax
salq$5, %rcx
addq%rdi, %rcx
movq$0, (%rcx)
movq$0, 8(%rcx)
movq$0, 16(%rcx)
movq$0, 24(%rcx)
movq$0, (%rdx)
movq$0, 8(%rdx)
movq$0, 16(%rdx)
movq$0, 24(%rdx)
addq$32, %rdx
cmpq%rsi, %rax
jne.L3
addq$64, %r8
addq$2048, %r9
cmpq$128, %r8
jne.L2
rep
ret

[Bug tree-optimization/46928] data dependence analysis fails on constant array accesses

[spop at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46928

--- Comment #3 from Sebastian Pop  2010-12-13 18:58:41 
UTC ---
Patch here:
http://gcc.gnu.org/ml/gcc-patches/2010-12/msg01016.html

[Bug tree-optimization/46928] data dependence analysis fails on constant array accesses

[xinliangli at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46928

davidxl  changed:

   What|Removed |Added

 CC||xinliangli at gmail dot com

--- Comment #2 from davidxl  2010-12-13 18:38:40 
UTC ---
Is memset guaranteed to be asynchronous safe? Otherwise such transformation is
not legal in signal handle code.

Icc does not covert it to memset, but unrolls differently -- this is where the
tuing in gcc should be done as well.

David

[Bug tree-optimization/46928] data dependence analysis fails on constant array accesses

[spop at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46928

Sebastian Pop  changed:

   What|Removed |Added

 Status|UNCONFIRMED |ASSIGNED
   Last reconfirmed||2010.12.13 18:09:36
 AssignedTo|unassigned at gcc dot   |spop at gcc dot gnu.org
   |gnu.org |
 Ever Confirmed|0   |1

--- Comment #1 from Sebastian Pop  2010-12-13 18:09:36 
UTC ---
Mine.

BTW, this PR comes from example 2 of http://blog.regehr.org/archives/320