Method using vector component comprising first and second bits to regulate movement of dependent instructions in a microprocessor

Abstract

A method and related apparatus is provided for a processor having a number of registers, wherein instructions are sequentially issued to move through a sequence of execution stages, from an initial stage to a final write back stage. As a method, an embodiment includes the step of issuing a first instruction, such as an FMA instruction, to move through the sequence of execution stages, the first instruction being directed to a specified one of the registers. The method further includes issuing a second instruction to move through the execution stages, the second instruction being issued after the first instruction has issued, but before the first instruction reaches the final write back stage. The second instruction is likewise directed to the specified register, and comprises either a store instruction or a load instruction, selectively. R and W bits corresponding to the specified register are used to ensure that a store instruction does not read data from, and that a load instruction does not write data to the specified register, respectively, before the first instruction is moved to the final write back stage.