[Bug tree-optimization/65511] New: transform_to_exit_first_loop

[Bug tree-optimization/65511] New: transform_to_exit_first_loop

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65511

            Bug ID: 65511
           Summary: transform_to_exit_first_loop
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: trivial
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org

before transform_to_exit_first_loop the loop backedge/exit edge probabilities
are 99/1:
...
  if (i.0_21 < n_5(D))
    goto <bb 9>;
  else
    goto <bb 6>;
;;    succ:       9 [99.0%]  (TRUE_VALUE,EXECUTABLE)
;;                6 [1.0%]  (FALSE_VALUE,EXECUTABLE)
...

afterwards, they are 100/0:
...
  # ivtmp_25 = PHI <0(11), ivtmp_23(7)>
  if (ivtmp_25 < _12)
    goto <bb 13>;
  else
    goto <bb 14>;
;;    succ:       13 [100.0%]  (TRUE_VALUE,EXECUTABLE)
;;                14 (FALSE_VALUE,EXECUTABLE)
...

[Bug tree-optimization/65511] transform_to_exit_first_loop looses edge probabilities

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65511

--- Comment #2 from vries at gcc dot gnu.org ---
using tentative patch, we get:
...
  if (ivtmp_25 < _12)
    goto <bb 13>;
  else
    goto <bb 14>;
;;    succ:       13 [99.0%]  (TRUE_VALUE,EXECUTABLE)
;;                14 [1.0%]  (FALSE_VALUE,EXECUTABLE)
...

[Bug tree-optimization/65511] transform_to_exit_first_loop looses edge probabilities

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65511

--- Comment #3 from vries at gcc dot gnu.org ---
testcase:
...
#define N 1000

unsigned int a[N];
unsigned int b[N];
unsigned int c[N];

void __attribute__((noclone,noinline))
f (unsigned int n)
{
  int i;

#pragma omp parallel
  {
#pragma omp for
    for (i = 0; i < n; ++i)
      c[i] = a[i] + b[i];
  }
}
...

compiled with -O2 -ftree-parallelize-loops=2

[Bug tree-optimization/65511] transform_to_exit_first_loop looses edge probabilities

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65511

--- Comment #6 from vries at gcc dot gnu.org ---
bootstrapped and reg-tested:
- https://gcc.gnu.org/ml/gcc-patches/2015-03/msg01536.html
- https://gcc.gnu.org/ml/gcc-patches/2015-03/msg01537.html

[Bug tree-optimization/65511] transform_to_exit_first_loop looses edge probabilities

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65511

--- Comment #7 from vries at gcc dot gnu.org ---
pinged patches at:
- https://gcc.gnu.org/ml/gcc-patches/2015-06/msg00976.html
- https://gcc.gnu.org/ml/gcc-patches/2015-06/msg00977.html