LLVM does not understand that inequality is transitive (even with constraint-elimination)

[jrmuizel]

GCC is able to eliminate the third assert in the following code:

#include <assert.h>
void f(int a, int b, int c) {
    assert(a < b);
    assert(b < c);
    assert(a < c);
}

https://gcc.godbolt.org/z/s9a9YM6GK

However, if I change the type from int to unsigned int LLVM is able to figure it out.

[thvdveld]

Looks like gcc 11.2 cannot eliminate the third assert when using unsigned int.
https://gcc.godbolt.org/z/Ph3bqjzbq

gcc 12 can do both.

[fhahn]

The reason this is not handled by constraint-elimination is that support for signed conditions is not available on main yet. I put up a patch for initial signed support: https://reviews.llvm.org/D118806

[fhahn]

Initial signed support landed in 0a781d9

[jrmuizel]

This seems fixed now.
https://gcc.godbolt.org/z/s9a9YM6GK