There is a new 8051 C compiler in beta test that beats Keil's compiler by 35% code size, and 14% speed, on the Dhrystone benchmark. And, there is no need to select a memory model or use special keywords to control data placement.
More details here: www.htsoft.com/.../silabs8051beta
Were you not, at least once in your (presumably) long career, been tempted to win a few nanos here and there by using a platform specific, nasty trick? the only "platform specific tricks" I have implemented are 'tricks' specific to the particular derivative I am working with. If a given derivative as far as platform specific has e.g. multiple datapointers and the compiler does not use them, I will, in a time critical application, go straight to assembler. And there I use very platform(derivative) specific trick.
If by platformk specific you refer to the (re the '51)stupid 'portability' (who has ever heard of a 'small embedded" project being 'ported') I confess that if the Keil compiler aloow me to specify DATA I do it.
Erik