1. A method in a data processing system for selectively prohibiting speculative conditional branch execution, said method comprising: selecting a particular type of conditional branch instruction; storing an indication within each instruction that is said particular type of conditional branch instruction; fetching, by a processor, a first instruction from code to be executed; determining whether said first instruction includes said indication; in response to determining that said instruction includes said indication: prohibiting speculative execution of said first instruction; resolving an actual location to which said first instruction will branch; and branching execution of said code to said actual location; speculatively executing conditional branch instructions that do not include said indication; and in response to determining that said instruction does not include said indication, speculatively executing said first instruction.