[Bug tree-optimization/101179] New: y % (x ? 16 : 4) and y % (4 << (2 * (bool)x)) produce different code

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101179

            Bug ID: 101179
           Summary: y % (x ? 16 : 4) and y % (4 << (2 * (bool)x)) produce
                    different code
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

These produces different assembly:

int f1(int y)
{
    const bool x = y % 100 == 0;
    return y % (x ? 16 : 4) == 0;
}

int f2(int y)
{
    const bool x = y % 100 == 0;
    return y % (4 << (x * 2)) == 0;
}

Since they do the same calculation, I would expect them to produce the same
code.

Currently f1 produces slightly smaller code for aarch64 and x86_64.

With Clang they produce the same code (but using cmov which might not be
optimal).