Constant propagation is not really cheating though: it's a completely safe and accurate optimization. We use that in the PPC->X86 Jit of the Dolphin Emulator to reduce register pressure and use the fact that X86 instructions can have 32 bit constants (while PPC is usually limited to 16 bit consts, and 32 bit values are loaded with 2 instructions: lis/ori). If you implement it properly, you can actually brag about it :) (we have an abstract object that can be either an X86 register or a constant value, and instruction handlers handle these two cases differently - when they can't, the constant is loaded to a register).

+1 for IDA Pro. It's a shame this software is so expensive. The UI is actually pretty decent when you get used to it, and there are a ton of good plugins.