[llvm-bugs] [Bug 33153] New: -polly-opt-isl -polly-parallel crashes for certain tile sizes

via llvm-bugs llvm-bugs at lists.llvm.org
Wed May 24 05:35:45 PDT 2017


https://bugs.llvm.org/show_bug.cgi?id=33153

            Bug ID: 33153
           Summary: -polly-opt-isl -polly-parallel crashes for certain
                    tile sizes
           Product: Polly
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Optimizer
          Assignee: polly-dev at googlegroups.com
          Reporter: mbdharan at gmail.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 18501
  --> https://bugs.llvm.org/attachment.cgi?id=18501&action=edit
nested_par.ll

For certain tile sizes, -polly-opt-isl generates nested OpenMP parallel loops
as below. Polly doesn't seem to correctly generate code to pack values in
struct that is being passed to the nested polly_subfn.

In IslNodeBuilder::createForParallel, when the code generation continues in the
nested subfunctions, the values that are being packed into the struct still
refer to their old values of the parent function, but they should refer to the
new Values of the current subfunction. 

One fix is to replace those old values which have a corresponding new values
stored in the IslNodeBuilder::ValueMap, while generating this code.

Is this a correct way to handle nested OpenMP parallel loops? 

opt -S -basicaa -polly-process-unprofitable -polly-ignore-aliasing
-polly-opt-isl -polly-vectorizer=polly --polly-parallel
-polly-pattern-matching-based-opts=false --polly-tile-sizes=11,32,32 
-polly-codegen -polly-codegen-verify=true -debug-only=polly-ast nested_par.ll 
:: isl ast :: simple_test :: %entry.split---%for.end10
[p_0, p_1] -> {  : -2147483648 <= p_0 <= 2147483647 and -2147483648 <= p_1 <=
2147483647 }
{ domain: "[p_0, p_1] -> { Stmt4[i0, i1] : 0 <= i0 < p_0 and 0 <= i1 < p_1 }",
child: { mark: "1st level tiling - Tiles", child: { schedule: "[p_0, p_1] -> [{
Stmt4[i0, i1] -> [(floor((i0)/11))] }, { Stmt4[i0, i1] -> [(floor((i1)/32))]
}]", permutable: 1, coincident: [ 1, 0 ], child: { mark: "1st level tiling -
Points", child: { schedule: "[p_0, p_1] -> [{ Stmt4[i0, i1] ->
[(-3*floor((i0)/11) + floor((3i0)/11))] }]", permutable: 1, coincident: [ 1 ],
options: "[p_0, p_1] -> { isolate[[i0, i1] -> [i2]] : i0 >= 0 and i1 >= 0 and
32i1 < p_1 and 0 <= i2 <= 1 and 11i2 <= -11 + 3p_0 - 33i0; atomic[0] }", child:
{ schedule: "[p_0, p_1] -> [{ Stmt4[i0, i1] -> [(i1 - 32*floor((i1)/32))] }]",
permutable: 1, child: { mark: "SIMD", child: { schedule: "[p_0, p_1] -> [{
Stmt4[i0, i1] -> [(i0 + floor((i0)/11) - 4*floor((3i0)/11))] }]", permutable:
1, coincident: [ 1 ] } } } } } } } }
if (p_0 <= 100)

    // 1st level tiling - Tiles
    #pragma omp parallel for
    for (int c0 = 0; c0 <= floord(p_0 - 1, 11); c0 += 1)
      for (int c1 = 0; c1 <= floord(p_1 - 1, 32); c1 += 1) {
        // 1st level tiling - Points
        {
          for (int c2 = 0; c2 <= min(1, -3 * c0 + 3 * p_0 / 11 - 1); c2 += 1)
            for (int c3 = 0; c3 <= min(31, p_1 - 32 * c1 - 1); c3 += 1) {
              // SIMD
              for (int c4 = 0; c4 <= 3; c4 += 1)
                Stmt4(11 * c0 + 4 * c2 + c4, 32 * c1 + c3);
            }
          if (p_0 >= 11 * c0 + 9 || 3 * p_0 % 11 >= 3)
            #pragma omp parallel for
            for (int c2 = 0; c2 <= min(2, -3 * c0 + (3 * p_0 - 3) / 11); c2 +=
1)
              for (int c3 = 0; c3 <= min(31, p_1 - 32 * c1 - 1); c3 += 1) {
                // SIMD
                if (c2 <= 1 && 33 * c0 + 11 * c2 + 10 >= 3 * p_0) {
                  for (int c4 = 0; c4 < p_0 - 11 * c0 - 4 * c2; c4 += 1)
                    Stmt4(11 * c0 + 4 * c2 + c4, 32 * c1 + c3);
                } else if (c2 == 2) {
                  for (int c4 = 0; c4 <= min(2, p_0 - 11 * c0 - 9); c4 += 1)
                    Stmt4(11 * c0 + c4 + 8, 32 * c1 + c3);
                }
              }
        }
      }

else
    {  /* original code */ }

Referring to an argument in another function!
  store [100 x float]* %data, [100 x float]** %polly.subfn.storeaddr.data
Referring to an argument in another function!
  store float* %mean, float** %polly.subfn.storeaddr.mean
Referring to an argument in another function!
  store i32 %n, i32* %polly.subfn.storeaddr.n
Polly generated function could not be verified. Add -polly-codegen-verify=false
to disable this assertion.
UNREACHABLE executed at
/home/bmohan/data/llvm_git/tools/polly/lib/CodeGen/CodeGeneration.cpp:89!
#0 0x00000000023d9a84 (opt+0x23d9a84)
#1 0x00000000023d9b17 (opt+0x23d9b17)
#2 0x00000000023d8044 (opt+0x23d8044)
#3 0x00000000023d93fc (opt+0x23d93fc)
#4 0x00007fe2a9de9fe0 __restore_rt (/usr/lib/libpthread.so.0+0x11fe0)
#5 0x00007fe2a8926a10 __GI_raise (/usr/lib/libc.so.6+0x33a10)
#6 0x00007fe2a892813a __GI_abort (/usr/lib/libc.so.6+0x3513a)
#7 0x0000000002362b73 (opt+0x2362b73)
#8 0x000000000275b7f1 (opt+0x275b7f1)
#9 0x000000000275c210 (opt+0x275c210)
#10 0x0000000002751a49 (opt+0x2751a49)
#11 0x0000000001682df5 (opt+0x1682df5)
#12 0x0000000001cf7daf (opt+0x1cf7daf)
#13 0x0000000001cf7f26 (opt+0x1cf7f26)
#14 0x0000000001cf8273 (opt+0x1cf8273)
#15 0x0000000001cf8927 (opt+0x1cf8927)
#16 0x0000000001cf8b1f (opt+0x1cf8b1f)
#17 0x000000000106757a (opt+0x106757a)
#18 0x00007fe2a8913511 __libc_start_main (/usr/lib/libc.so.6+0x20511)
#19 0x000000000104b98a (opt+0x104b98a)
Stack dump:
0.      Program arguments: opt -S -basicaa -polly-process-unprofitable
-polly-ignore-aliasing -polly-opt-isl -polly-vectorizer=polly --polly-parallel
-polly-codegen-verify=false -polly-pattern-matching-based-opts=false
--polly-tile-sizes=11,32,32 -polly-codegen -polly-codegen-verify=true
-debug-only=polly-ast /home/bmohan/Downloads/polly_tiling_test/nested_par.ll 
1.      Running pass 'Function Pass Manager' on module
'/home/bmohan/Downloads/polly_tiling_test/nested_par.ll'.
2.      Running pass 'Region Pass Manager' on function '@simple_test'
3.      Running pass 'Polly - Create LLVM-IR from SCoPs' on basic block
'%entry.split'

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