Shift operation is undefined if the shift count greater than or equals to the length in bits of the promoted left operand. https://stackoverflow.com/a/18918340/5262383

 

Here is an example:

static int test_shift(int nbit) { return 1U << nbit;}

static int test_shift_32() {  return 1U << 32;}

int main(int argc, char **argv) {
  int r;
  r = test_shift(32); 
  printf("%d\n", r);  // 1
  r = test_shift_32(); 
  printf("%d\n", r);  // 0
  return 0;
}
 

For c2, Instruction_aarch64::patch(https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/aarch64/assembler_aarch64.hpp#L218)&#xA0;shared the same problem. 

// piece of code from assembler_aarch64.hpp
 static void patch(address a, int msb, int lsb, uint64_t val) {
    int nbits = msb - lsb + 1;
    guarantee(val < (1ULL << nbits), "Field too big for insn");
    assert_cond(msb >= lsb);
    unsigned mask = (1U << nbits) - 1;
    val <<= lsb;
    mask <<= lsb;
    unsigned target = *(unsigned *)a;
    target &= ~mask;
    target |= val;
    *(unsigned *)a = target;
  }
  When someone intends to patch an entire instruction with msb=31, lsb=0, there would be   an unexpected result.