Instruction Flow

Pixel shader versions 1.0, 1.1, 1.2, and 1.3 allow four types of instructions. The instructions must appear in the order shown below.

Pixel shader version 1.4 adds a phase instruction that allows double the number of texture addressing and arithmetic instructions. The shader is separated into phase 1 and phase 2 by a phase marker. Each phase begins with up to six texture instructions, followed by up to eight arithmetic instructions. If a shader does not contain a phase marker, the shader behaves as if all the instructions are phase 2 instructions.

The structure of a pixel shader version 1.4 shader is therefore:

• Version instruction (ps.1.4)
• Constant instructions
• Up to six texture addressing instructions
• Up to eight arithmetic instructions
• Phase marker
• Up to six texture addressing instructions
• Up to eight arithmetic instructions

The unfortunate side-effect of the phase transition is that the alpha component of temporary registers are unset or uninitialized during the transition. For additional information, see the phase instruction.