What variable types I should NOT use in iPhone code?

Can't find it now, but I recall I should avoid using 开发者_开发问答double variables in iPhone coding for (poor) performance reasons? Is this true? Are there any other known problems with some variable types?

Using float or double on embedded devices is slow when there is no FPU.

About floating point performance on the iPhone, you can have a look at Break That Thumb For Best iPhone Performance and Cranking Up Floating Point Performance To 11: it deals with floating point performance and floating point operations causing the program to switch back and forth between Thumb mode and regular 32-bit mode.

See also Squeezing Every Drop Of Performance Out Of The iPhone.