[ Thanks to Michael Larabel for
this link. ]
“LLVM-GCC is a C front-end for the Low-Level Virtual
Machine but its back-end is a modified version of GCC (4.2). LLVM
has its own compiler front-end, clang, for C and C++, but it is not
nearly as complete or mature as the GNU Compiler Collection. Clang
has been improving in recent times, but some portions are still
incomplete (largely with C++). LLVM-GCC is provided with Xcode 3.2
found in Mac OS X 10.6, but it can also be found in several
distribution package repositories, including Ubuntu. Apple though
is the primary sponsor of the Low-Level Virtual Machine. LLVM/Clang
is actually replacing GCC in FreeBSD Base. While we are not testing
Clang in this article, for a comparison of Clang against GCC, read
LLVM’s comparison. Additional information on this open-source
compiler infrastructure is available from the project’s web-site.
LLVM is also used by Apple in their OpenCL implementation and is
finding uses on Linux within Gallium3D.“For this benchmarking we used several test profiles from the
Phoronix Test Suite that are written in C and are built from source
during their installation procedure. Prior to running one of the
tests, we set the default compiler to GCC 4.2.1 (Apple Build 5646)
and then set the default compiler to LLVM-GCC (GCC 4.2.1, Apple
Build 5646, LLVM Build 2118) prior to reinstalling the tests. With
the resulting binaries from GCC and LLVM-GCC, we then looked at
their performance. Compiler flags and other settings were
maintained the same. These tests included LAME MP3 encoding, dcraw,
OpenSSL, BYTE Unix Benchmark, John The Ripper, timed MAFFT
alignment, Crafty, TSCP, Tachyon, and C-Ray.”