In #149619, for the test of `@dot_follow_modulo_spec_2`, constant
folding the addition of two i32 1073741824 causes an overflow from 2^32
to -2^32=-2147483648, which triggers the UB sanitizer. This PR reapplies
the previous PR, explicitly casting the addition operand to int64_t
first before performing the addition before producing a int32 number via
`Constant *C = get(cast<IntegerType>(Ty->getScalarType()), V, isSigned)`
10d9e7b1b7