[Bug tree-optimization/111780] New: Missed optimization of '(t*4)/(t*2) -> 2'

["652023330028 at smail dot nju.edu.cn" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111780

            Bug ID: 111780
           Summary: Missed optimization of '(t*4)/(t*2) -> 2'
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 652023330028 at smail dot nju.edu.cn
  Target Milestone: ---

Hello, we found some optimizations (regarding Arithmetic optimization) that GCC
may have missed. We would greatly appreicate if you can take a look and let us
know what you think.

Given the following code:
https://godbolt.org/z/G9rWK7c3q
int n1;
void func1(int a){
    if(a>1&&a<4) n1=(a+a+a+a)/(a+a);
}

Different from PR 111718, this missed optimization appears to be due to a
missed pattern: (t*4)/(t*2) -> 2

  # DEBUG BEGIN_STMT
  # RANGE [irange] int [8, 8][12, 12] NONZERO 0xc
  _3 = a_7(D) * 4;
  # RANGE [irange] int [4, 4][6, 6] NONZERO 0x6
  _4 = a_7(D) * 2;
  # RANGE [irange] int [1, 3] NONZERO 0x3
  _5 = _3 / _4;
  # .MEM_9 = VDEF <.MEM_8(D)>
  n1D.2761 = _5;

Or a more general pattern: (t*m)/(t*n) -> m/n , where m and n are constants.

Thank you very much for your time and effort! We look forward to hearing from
you.