[LLVMdev] Stupid '-load-vn -licm' question (LLVM 1.6)

[Chris Lattner]

On Fri, 17 Mar 2006, Eric Kidd wrote:
>> I'm particularly confused by the rlwinm instructions that keep turning up 
>> in PowerPC output, and the double test against 98. I don't have a problem 
>> or anything; I'm just trying to figure out what's going on. :-)
>
> Ah! The backend is running -lowerswitch, which does a binary search of the 
> case labels (even when there's only two of them).

yup

> If I run -lowerswitch manually, though, I *do* get some very nice results out 
> of -cee. :-) It's automatically killing some backtrack nodes in my CFG, which 
> is a big (and unexpected) win.

Great.  Note that -cee is a beta pass... it has some known bugs and isn't 
planned to be worked on in the immediate future. :(

> Overall, I'm extremely impressed with the LLVM optimizer framework--even when 
> it does something weird, it's easy to dive in and read the code. In the past, 
> I've spent months working on compiler backends before feeling this 
> comfortable.

Great!  I'm glad to hear that!

-Chris

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