15 ms·

Does it? http://imagine-rt.blogspot.co.uk/2014/12/c-compiler-benchmarks.html http://imagine-rt.blogspot.co.uk/2014/12/c-compiler-benchmar...

phkahler 12y ago
Why yes, yes it does. There are exceptions of course, you seem to have found one. Here are some others: http://www.phoronix.com/scan.php?page=article&item=gcc49_compiler_llvm35&num=1 http://www.phoronix.com/scan.php?page=article&item=gcc49_com...
sanxiyn 12y ago
Yes it does. Did you read my links? Small benchmarks can go either way, but for large codebase (especially C++) inliner is more important than just about anything else. So GCC wins, because it has better inliner.
- darkpore 12y ago
  Yep - you evidently didn't read mine as 165 k lines of c++ isn't exactly a small benchmark :) Anecdotal, but I've seen similar improvements over g++ in my code.
  - sanxiyn 12y ago
    There are many measures of benchmark sizes. One important measure is size of codes that account for 99% of execution time. If your codebase is a million lines but your hotspot is a thousand lines, benchmark result is sensitive to optimization quirks and in some sense benchmark is small. More on this idea here: http://blog.pyston.org/2014/12/05/python-benchmark-sizes/ http://blog.pyston.org/2014/12/05/python-benchmark-sizes/
- darkpore 12y ago
  Yep - you evidently didn't read mine as 165 k lines of c++ isn't exactly a small benchmark :) Anecdotal, but I've seen similar improvements over g++ in my code.
berkut 12y ago
As the original author of that benchmark, I should point out that that was LLVM SVN (unreleased) against GCC 4.8 & 4.9 - I couldn't get GCC 5.0 SVN to build, so it's possible 5.0 will be faster again than LLVM in certain situations. However, I would also say that generally I've found LLVM is now producing faster code than GCC in most code I've tested both compilers with.
- sanxiyn 12y ago
  That is very interesting, because LLVM developers themselves admit LLVM generates slower code than GCC (in average). This is plain if you read LLVM Developers' Meeting talks. I think it is completely possible that LLVM developers are using wrong benchmarks. Benchmarks are mostly SPEC and some large Google C++ codebases; in some sense both are quite atypical. But then, entire problem is to understand how typical codebases look like.
  - DannyBee 12y ago
    I can hopefully settle this (as a developer of both). Assuming we stick to x86/x64, nowadays (literally, let's say as of January 2015) GCC and LLVM are within the noise for most people on most code (IE 1-2% of each other). You can certainly find benchmarks were LLVM does badly. Some are important to some people, some aren't. It is harder to find benchmarks where GCC does badly.

phkahler 12y ago

Why yes, yes it does. There are exceptions of course, you seem to have found one. Here are some others: http://www.phoronix.com/scan.php?page=article&item=gcc49_compiler_llvm35&num=1 http://www.phoronix.com/scan.php?page=article&item=gcc49_com...

sanxiyn 12y ago

Yes it does. Did you read my links? Small benchmarks can go either way, but for large codebase (especially C++) inliner is more important than just about anything else. So GCC wins, because it has better inliner.

darkpore 12y ago
Yep - you evidently didn't read mine as 165 k lines of c++ isn't exactly a small benchmark :) Anecdotal, but I've seen similar improvements over g++ in my code.
- sanxiyn 12y ago
  There are many measures of benchmark sizes. One important measure is size of codes that account for 99% of execution time. If your codebase is a million lines but your hotspot is a thousand lines, benchmark result is sensitive to optimization quirks and in some sense benchmark is small. More on this idea here: http://blog.pyston.org/2014/12/05/python-benchmark-sizes/ http://blog.pyston.org/2014/12/05/python-benchmark-sizes/
darkpore 12y ago
Yep - you evidently didn't read mine as 165 k lines of c++ isn't exactly a small benchmark :) Anecdotal, but I've seen similar improvements over g++ in my code.

berkut 12y ago

As the original author of that benchmark, I should point out that that was LLVM SVN (unreleased) against GCC 4.8 & 4.9 - I couldn't get GCC 5.0 SVN to build, so it's possible 5.0 will be faster again than LLVM in certain situations. However, I would also say that generally I've found LLVM is now producing faster code than GCC in most code I've tested both compilers with.

sanxiyn 12y ago
That is very interesting, because LLVM developers themselves admit LLVM generates slower code than GCC (in average). This is plain if you read LLVM Developers' Meeting talks. I think it is completely possible that LLVM developers are using wrong benchmarks. Benchmarks are mostly SPEC and some large Google C++ codebases; in some sense both are quite atypical. But then, entire problem is to understand how typical codebases look like.
- DannyBee 12y ago
  I can hopefully settle this (as a developer of both). Assuming we stick to x86/x64, nowadays (literally, let's say as of January 2015) GCC and LLVM are within the noise for most people on most code (IE 1-2% of each other). You can certainly find benchmarks were LLVM does badly. Some are important to some people, some aren't. It is harder to find benchmarks where GCC does badly.