[Bug tree-optimization/81423] New: Wrong code at -O2

["babokin at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81423

            Bug ID: 81423
           Summary: Wrong code at -O2
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: babokin at gmail dot com
  Target Milestone: ---

gcc trunk, rev250140, x86_64.

Test case has no undefined behavior, but -O2 produces incorrect result.

> cat f.cpp
#include <iostream>

unsigned long long int ll = 0;
unsigned long long int ull1 = 1ULL;
unsigned long long int ull2 = 12008284144813806346ULL;
unsigned long long int ull3;

void foo() {
  ll = -5597998501375493990LL;

  ll = unsigned(5677365550390624949L - ll) - (ull1 > 0);
  ull3 = unsigned(2067854353L << (((ll + -2129105131L) ^
10280750144413668236ULL) - 10280750143997242009ULL)) >>
((2873442921854271231ULL | ull2) - 12098357307243495419ULL);
}

int main() {
  foo();
  std::cout << ull3 << " (expected 3998784)\n";
  return 0;
}

> g++ f.cpp -O0 -o out; ./out
3998784 (expected 3998784)

> g++ f.cpp -O2 -o out; ./out
3493659712 (expected 3998784)