llvm dev - Jun 2013 - [LLVMdev] does clang and llvm take more time to compile c code

Hello, all

When I compile mpeg2enc of Mediabench, it seems clang and llvm take longer
time than gcc. I meausre the time as follow:

gcc -O3   8.190s
clang  -O3  20.253s

will this means clang and llvm are slower than gcc in compiling c code.


Eric
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On 27.06.2013, at 13:40, Eric Lu <eirc.lew at gmail.com> wrote:
> Hello, all
> 
> When I compile mpeg2enc of Mediabench, it seems clang and llvm take longer
time than gcc. I meausre the time as follow:
> 
> gcc -O3   8.190s
> clang  -O3  20.253s
> 
> will this means clang and llvm are slower than gcc in compiling c code.
Possibly. The timings are useless without information about the versions of GCC
and clang used and the build configuration (clang is extremely slow when built
without optimization).

- Ben

Hi, Ben
gcc version is: 4.7.0
clang version is: 3.2

The command options are:
1) clang
generated object files: clang -O3 -c *.c -o x.o
link:  clang  *.o -lm -o  mpeg2enc

2) gcc
generated object files: gcc -O3 -c *.c -o x.o
link:  gcc  *.o -lm -o  mpeg2enc


Yes, maybe it is the config introduced problems, I build it with enable
debug options.

Thanks!

Eric




On Thu, Jun 27, 2013 at 7:49 PM, Benjamin Kramer <benny.kra at
gmail.com>wrote:
>
> On 27.06.2013, at 13:40, Eric Lu <eirc.lew at gmail.com> wrote:
>
> > Hello, all
> >
> > When I compile mpeg2enc of Mediabench, it seems clang and llvm take
> longer time than gcc. I meausre the time as follow:
> >
> > gcc -O3   8.190s
> > clang  -O3  20.253s
> >
> > will this means clang and llvm are slower than gcc in compiling c
code.
>
> Possibly. The timings are useless without information about the versions
> of GCC and clang used and the build configuration (clang is extremely slow
> when built without optimization).
>
> - Ben
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