Patent ID: 7240185

Claim:
A computer system for executing predicated instructions wherein each instruction includes a guard, the value of which determines whether or not that instruction is executed, the computer system comprising: a fetch unit for fetching instructions to be executed; a decode unit for decoding said instructions; at least one pipelined execution unit for executing decoded instructions and being associated with a guard register file holding values of the guards to allow resolution of the guards to be made; and an emulation unit including control circuitry which cooperates with the decode unit to selectively control the decode unit to implement a precise watch mode or a non-precise watch mode on detection of a breakpoint caused by a fetched instruction having a specified program count or a fetched instruction having a specified opcode, wherein when the decode unit implements the precise watch mode, the fetched instruction causing the breakpoint and at least one subsequent instruction are not permitted to be executed until after a guard value associated with the fetched instruction is resolved and, when the decode unit implements the non-precise watch mode, the instruction causing the breakpoint and at least one subsequent instruction are permitted to be executed before the guard value associated with the fetched instruction is resolved.