JIT: Unnecessary bounds checks for MD array accesses

[jakobbotsch]

For code like:

void Foo(int[,] foo)
{
    for (int i = foo.GetLowerBound(0); i < foo.GetUpperBound(0); i++)
    {
        int count = i * 100;

        for (int j = foo.GetLowerBound(1); j < foo.GetUpperBound(1); j++)
        {
            foo[i, j] = count++;
        }
    }
}

we generate unnecessary bounds checks on the accesses within the loop. This pattern is also what Roslyn produces for foreach over MD arrays, so we should be able to optimize it better.

Reported by @richlander

category:cq theme:md-arrays skill-level:expert cost:large

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