Comments on: ARM compiler shoot-out, round 2

By: Mans

Mans — Wed, 18 Nov 2009 12:25:00 +0000

I already said I’m using –translate_gcc which maps -O3 to -O3 -Otime.

By: Marcus Harnisch

Marcus Harnisch — Wed, 18 Nov 2009 09:19:12 +0000

Just as a reminder: Unlike gcc, armcc optimizes for space by default. Please also specify -Otime to make sure it directs its effort to execution time. Please check this out, too. No guarantees, though.

By: Anton Korobeynikov

Anton Korobeynikov — Fri, 13 Nov 2009 13:12:39 +0000

Sorry, I really have no idea what you’ve downloaded. Release tarballs contains all the code from the SVN repository. For ARM stuff you might really want do checkout code from SVN, since after the 2.6 release bunch of stuff was fixed / improved.

By: Mans

Mans — Thu, 12 Nov 2009 21:27:30 +0000

That is most definitely not what was in a tarball I downloaded. The only instructions I found involved a complicated procedure combining parts from an llvm base tarball with some llvm-gcc bits, and none of it made much sense, so I gave up.

By: Anton Korobeynikov

Anton Korobeynikov — Thu, 12 Nov 2009 21:19:10 +0000

Huh, how so? There is definitely one:
http://llvm.org/viewvc/llvm-project/llvm-gcc-4.2/trunk/configure

Make sure you checked out stuff properly. README.LLVM is also a good thing to read before building.

There is a script for almost automatic build of cross-compilers. See http://llvm.org/viewvc/llvm-project/llvm/trunk/utils/crosstool/ARM/README

By: Mans

Mans — Thu, 12 Nov 2009 13:36:18 +0000

I see nothing usual about building llvm-gcc. There isn’t even a configure script.

By: Anton Korobeynikov

Anton Korobeynikov — Thu, 12 Nov 2009 13:18:09 +0000

Build llvm-gcc as usual gcc. There is even script to use codesourcery-provided binutils as a “bootstrap” toolchain.

By: Mans

Mans — Tue, 10 Nov 2009 13:08:32 +0000

Most of the compilers support only softfp ABI. I compared soft and hard with gcc-csl 2009q1, and there was very little difference. FFmpeg passes floats as arguments or return values in very few places.

I’m planning a new round soon, and I’d be happy to include LLVM, if only I could figure out how to configure it as a cross-compiler.

By: Anton Korobeynikov

Anton Korobeynikov — Tue, 10 Nov 2009 12:57:51 +0000

Why are you using softfp ABI for the benchmarks? Hardware FP ABI is much better suited for such of applications and might yield a noticeable speedup.

PS: Could you please also include LLVM for the tests?

By: Reimar

Reimar — Tue, 25 Aug 2009 13:01:41 +0000

s/incredibly bad/useless/
Really, you just can’t use gcc to do multiplications larger than the native size if speed or code size are in any way relevant.