C++: Only propagate smallest/largest range bound in conditional expressions #18461
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This PR changes how bounds are propagated for the ternary operator.
Currently, for
c ? e1 : e2the union of the bounds fore1ande2are propagated. With this change the bounds are combined with the smallest/greatest (for lower bounds/upper bounds respectively) being propagated.Hence the number of bounds for
c ? e1 : e2changes from|e1| + |e2|to|e1| * |e2|. This is good when the number of bounds is 1 and worse otherwise. DCA will hopefully tell of if the overall impact is good or bad.