Bounds check is not eliminated ssize vs size

[Kojoley]

#define _GLIBCXX_ASSERTIONS
#include <vector>

void foo(std::vector<double> &vec)
{
   auto count = ssize(vec);
   for (decltype(count) i = 0; i < count; ++i)
     vec[i] += 1;
}

-mllvm -enable-constraint-elimination does not help.
With size instead of ssize bounds check is eliminated.
https://godbolt.org/z/f5Gn9eKrc

[fhahn]

To catch this in constraint-elimination, we need to use the info that the phi node will always be signed positive (due to the increment not wrapping). Looking.

[fhahn]

Put up PR (#72879) to solve this in Constraintelimination, but this is now also handled by IndVarSimplify