Methods and systems to convert scalar computer program loops having loop carried dependences to vector computer program loops are disclosed. One example method and system generates a first predicate set associated with a first conditionally executed statement. The first predicate set contains a first set of predicates that cause a variable to be defined in a scalar computer program loop at or before the variable is defined by the first conditionally executed statement. The method and system also generates a second predicate set associated with the first conditionally executed statement. The second predicate set contains a second set of predicates that cause the variable to be used in the scalar computer program loop at or before the variable is defined by the first conditionally executed statement. The method and system determines whether the second predicate set is a subset of the first predicate set and, based on the determination, propagates a vector value in an element of a vector of the variable to a subsequent element of the vector.