[Bug tree-optimization/67607] New: Failure to perform constant folding through type conversion

[miyuki at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67607

            Bug ID: 67607
           Summary: Failure to perform constant folding through type
                    conversion
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: miyuki at gcc dot gnu.org
  Target Milestone: ---

This code is taken from PR67606:

$ cat pr67606.c
int f(int a[], int length)
{
  int count=0;
  for (int i = 0 ; i < length ; i++)
    if (a[i] > 5)
      count++;

  return count;
}

$ g++ -S -O3 -fno-tree-vectorize pr67606.c -fverbose-asm -fdump-tree-optimized

We get:

  <bb 3>:
  ivtmp.6_1 = (unsigned long) a_7(D);
  _19 = (unsigned int) length_4(D);
  _18 = _19 + 4294967295;
  _21 = (sizetype) _18;
  _22 = _21 + 1;
  _23 = _22 * 4;
  _24 = a_7(D) + _23;
  _25 = (unsigned long) _24;

And this leads to generating some redundant code:

  leal    -1(%rsi), %eax  #, tmp114
  leaq    4(%rdi,%rax,4), %rcx    #, tmp111