[LLVMdev] PR723: Default To Optimized Build

[Chris Lattner]

On Mon, 27 Mar 2006, Eric van Riet Paap wrote:
> I think using different settings is generally (and this this case too) a bad 
> idea because it makes things more complicated. All developers know how to 
> build LLVM. Most (new/casual) users expect a certain behaviour and they will 
> judge LLVM on subjective grounds. If linking/performance suffers they will 
> continue looking for whatever gives them that extra bit of performance. 
> People like me that take the time to file bugreport are willing to invest 
> time in LLVM and are most probably also willing to recompile a full-debug 
> LLVM.

I agree, but there is a balance here:

Users almost ALWAYS use releases.
Developers almost ALWAYS use CVS.

Also, developers configure a lot more often than users ;)

-Chris

> On Mar 27, 2006, at 9:09 PM, Chris Lattner wrote:
>
>> On Mon, 27 Mar 2006, Andrew Lenharth wrote:
>>>> Another option is to build an optimized build with assertions on.  Do to
>>>> local demand, I added a build option 'make ENABLE_OPTIMIZED=1
>>>> ENABLE_ASSERTIONS=1' that provides this.
>>> 
>>> How does this compare size and performance wise with a debug build or a
>>> release build?
>> 
>> I haven't done any scientific measurements.  Here is some educated guessing 
>> :)
>> 
>> I know that a debug build is about 10x bigger and 10x slower than a release 
>> build.  Linking also takes about 10x as long with a debug build than it 
>> does for a release build.
>> 
>> With assertions on, linking takes virtually the same time as a release 
>> build, I would expect it to also be about the same speed as a release 
>> build: a WAG would be within 10%.
>> 
>> For the people that requested the optimized+assertions build, the big issue 
>> was link-time.  Having a huge link time significantly impacted their 
>> productivity and they happened to not care about performance for most 
>> development.  OTOH, not getting assertions was preventing them from finding 
>> bugs.
>> 
>> The more I think about it, the more I like a configuration that looks like 
>> this:
>> 
>> 'llvm --enable-optimized' should always build a release build.
>> 
>> LLVM from CVS should always default to a debug build.
>> 
>> LLVM releases should default to 'release + assertions'.
>> 
>> Thoughts?
>> 
>> -Chris
>> 
>> -- 
>> http://nondot.org/sabre/
>> http://llvm.org/
>> 
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-Chris

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