You'll need to examine the binary generated for a particular architecture by the driver. It may work on one driver+GPU combination, but be slower on another. Al

You'll need to examine the binary generated for a particular architecture by the driver. It may work on one driver+GPU combination, but be slower on another. Also, the semantics for floating-point math are somewhat looser in GLSL so the driver is given more power to reorder expressions and might exploit this trick on its own. As usual, you should profile and benchmark.