[LLVMdev] speed and code size issues

Jonathan Gray jsg at goblin.cx
Fri Jul 17 18:18:47 PDT 2009


Yes, a full list which includes some generated .h files can
be found at
http://goblin.cx/llvm/
specifically
http://goblin.cx/llvm/LLVM-bakeoff-clang-hsize
http://goblin.cx/llvm/LLVM-bakeoff-gcc335-hsize
http://goblin.cx/llvm/LLVM-bakeoff-gcc424-hsize
http://goblin.cx/llvm/LLVM-bakeoff-llvmgcc-hsize

drop -hsize for the plain sizes.

http://goblin.cx/llvm/LLVM-bakeoff-comparison
has these merged into a single line format of the form

if_spppsubr.o, clang: 124440, gcc335: 48968, gcc424: 49272, llvmgcc: 120400

On Fri, Jul 17, 2009 at 05:46:20PM -0700, Dale Johannesen wrote:
> I'd look at  if_spppsubr.o, which is big in the llvm directories and  
> doesn't appear in the gcc directory listings at all (I assume the  
> listings were fed through tail or something, but there's clearly a  
> sizeable difference there)
> 
> On Jul 17, 2009, at 5:41 PMPDT, Daniel Dunbar wrote:
> 
> > On Fri, Jul 17, 2009 at 5:12 PM, Jonathan Gray<jsg at goblin.cx> wrote:
> >> On Fri, Jul 17, 2009 at 04:41:55PM -0700, Eli Friedman wrote:
> >>> On Fri, Jul 17, 2009 at 4:14 PM, Jonathan Gray<jsg at goblin.cx> wrote:
> >>>> This seems to go against notes such as
> >>>> http://clang.llvm.org/features.html#performance
> >>>> which claim clang is signifcantly faster than gcc.
> >>>
> >>> I think the URL you want is actually
> >>> http://clang.llvm.org/performance.html.  The difference isn't as
> >>> dramatic when you consider code generation, at least for the moment.
> >>
> >> Are these scripts to break down the time spent
> >> in different stages available somewhere?
> >
> > Not currently, I've never bothered to make them public because they
> > aren't very generic. They more or less amount to running the compiler
> > with extra options like -fsyntax-only, or -E, and timing those. Its
> > worth trying to reproduce the performance issue on a single file
> > before going down this road. However, if you really want them I can
> > ship you what I have, I just don't promise it will be very useful.
> >
> > - Daniel
> >
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