Switch default destination not eliminated despite known value range

[mattiase]

A fully populated switch with known value range (but no explicit default clause) will still generate a conditional jump to the default destination:

void canthappen(void);
int g(int);

int f(int x) {
  if (x >= 0 && x <= 3) {
    switch (x) {
    case 0: return g(2);
    case 1: return g(3);
    case 2: return g(4);
    case 3: return g(5);
    }
    canthappen();
  }
  return -23;
}

results in a never-taken conditional branch to code that calls canthappen.
llvm 18.0.0git (9f74e6e).

[nikic]

https://llvm.godbolt.org/z/bMc4xv5dW

[mattiase]

Nice, thank you!