A computer has instruction pipeline circuitry capable of executing two instruction set architectures (ISA's). A binary translator translates at least a selected portion of a computer program from a lower-performance one of the ISA's to a higher-performance one of the ISA's. Hardware initiates a query when about to execute a program region coded in the lower-performance ISA, to determine whether a higher-performance translation exists. If so, the about-to-be-executed instruction is aborted, and control transfers to the higher-performance translation. After execution of the higher-performance translation, execution of the lower-performance region is reestablished at a point downstream from the aborted instruction, in a context logically equivalent to that which would have prevailed had the code of the lower-performance region been allowed to proceed.