Method and apparatus for executing a predefined instruction set

In a programmable vertex shader comprising a controller coupled to a programmable vertex shader engine and a two-port temporary register memory coupled to the programmable vertex shader engine, a method for executing a three-input operand MADD (multiply and add) instruction that requires three-input operands at a time from the two-port temporary register memory, the method comprising:

• recognizing, by the controller, occurrence of the thee-input operand MADD instruction requiring the three-input operands from the two-port temporary register memory;
• providing, by the controller to the programmable vertex shader engine, a substitute two input operand MUL instruction and a substitute three-input operand MADD instruction;
• executing, by the programmable vertex shader engine, the substitute two input operand MUL instruction using no more than two input operands at a time from the two-port temporary register memory to provide an intermediate result;
• temporarily storing, by the programmable vertex shader engine, the intermediate result;
• and
• executing, by the programmable vertex shader engine, the substitute three-input operand MADD instruction using no more than two input operands at a time from the two-port temporary register memory.

A programmable vertex shader comprising:

• a programmable vertex shader engine;
• a code memory comprising a plurality of instructions for execution by the programmable vertex shader engine;
• an n-output temporary register memory, coupled to the programmable vertex shader engine, that provides as output no more than n operands at a time;
• and
• a programmable vertex shader controller, coupled to the code memory and the programmable vertex shader engine, that receives the plurality of instructions and monitors the plurality of instructions for occurrence of at least one (n+m) input operand instruction that requires (n+m) input operands from the n-output temporary register memory,
• wherein the programmable vertex shader controller provides at least two substitute instructions to the programmable vertex shader engine upon detecting the at least one (n+m) input operand instruction that requires the (n+m) input operands from the n-output temporary register memory,
• and wherein each of the at least two substitute instructions requires no more than n-input operands from to n-output temporary register memory.

An apparatus for executing a predefined code set which includes at least one (n+m) input operand instruction that requires (n+m) input operands at a time, the apparatus comprising:

• means for recognizing occurrence of the at least one (n+m) input operand instruction in which the (n+m) input operands are received from an n-output data source that provides no more than n operands at a time;
• means, responsive to the means for recognizing, for providing at least two substitute instructions in place of the at least one (n+m) input operand instruction in which the (n+m) input operands are received from the n-output data source, wherein each of the at least two substitute instructions requires no more than n-input operands from the n-output data source;
• and
• means, coupled to the means for providing, for executing a first of the at least two substitute instructions using no more than n-input operands from the n-output data source to provide an intermediate result, and for executing another of the at least two substitute instructions using the intermediate result and no more than a operands from the n-output data source.