First, LLVM comes in two pieces. The first piece is the LLVM suite. This contains all of the tools, libraries, and header files needed to use the low -level virtual machine. It contains an assembler, disassembler, bytecode -analyzer and bytecode optimizer. It also contains a test suite that can be +level virtual machine. It contains an assembler, disassembler, bitcode +analyzer and bitcode optimizer. It also contains a test suite that can be used to test the LLVM tools and the GCC front end.
The second piece is the GCC front end. This component provides a version of -GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front +GCC that compiles C and C++ code into LLVM bitcode. Currently, the GCC front end uses the GCC parser to convert code to LLVM. Once -compiled into LLVM bytecode, a program can be manipulated with the LLVM tools +compiled into LLVM bitcode, a program can be manipulated with the LLVM tools from the LLVM suite.
@@ -114,13 +114,13 @@ and performance.
The LLVM suite may compile on other platforms, but it is not guaranteed to do so. If compilation is successful, the LLVM utilities should be -able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code +able to assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation should work as well, although the generated native code may not work on your platform.
The GCC front end is not very portable at the moment. If you want to get it to work on another platform, you can download a copy of the source and try to compile it on your platform.
+href="GCCFEBuildInstrs.html">try to compile it on your platform. @@ -469,7 +474,6 @@ href="CFEBuildInstrs.html">try to compile it on your platform.GCC 3.2.2: This version of GCC fails to compile LLVM.
+GCC 3.2.2 and 3.2.3: These versions of GCC fails to compile LLVM with +a bogus template error. This was fixed in later GCCs.
GCC 3.3.2: This version of GCC suffered from a serious bug which causes it to crash in the "convert_from_eh_region_ranges_1" GCC function.
Cygwin GCC 3.3.3: The version of GCC 3.3.3 commonly shipped with - Cygwin does not work. Please upgrade + Cygwin does not work. Please upgrade to a newer version if possible.
SuSE GCC 3.3.3: The version of GCC 3.3.3 shipped with SuSE 9.1 (and possibly others) does not compile LLVM correctly (it appears that exception handling is broken in some cases). Please download the FSF 3.3.3 or upgrade to a newer version of GCC.
-GCC 3.4.0 on linux/x86 (32-bit): GCC miscompiles portions of the +
GCC 3.4.0 on linux/x86 (32-bit): GCC miscompiles portions of the code generator, causing an infinite loop in the llvm-gcc build when built with optimizations enabled (i.e. a release build).
-GCC 3.4.2 on linux/x86 (32-bit): GCC miscompiles portions of the +
GCC 3.4.2 on linux/x86 (32-bit): GCC miscompiles portions of the code generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0) correctly compiles LLVM at -O2. A work around is to build release LLVM builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."
-GCC 3.4.x on X86-64/amd64: GCC
+ GCC 3.4.x on X86-64/amd64: GCC
miscompiles portions of LLVM. GCC 3.4.4 (CodeSourcery ARM 2005q3-2): this compiler miscompiles LLVM
+ when building with optimizations enabled. It appears to work with
+ "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1" or build a debug
+ build. IA-64 GCC 4.0.0: The IA-64 version of GCC 4.0.0 is known to
miscompile LLVM. Apple Xcode 2.3: GCC crashes when compiling LLVM at -O3 (which is the
@@ -629,11 +638,11 @@ In order to compile and use LLVM, you may need to set some environment
variables.
-
@@ -691,8 +700,8 @@ follows:
If you want to get a specific release (as opposed to the most recent -revision), you can specify a label. The following releases have the following -labels:
+revision), you can checkout it from the 'tags' directory (instead of +'trunk'). The following releases are located in the following + subdirectories of the 'tags' directory:If you would like to get the LLVM test suite (a separate package as of 1.4), you get it from the Subversion repository:
+ +- cd llvm/projects - svn so http://llvm.org/svn/llvm-project/test-suite/trunk test-suite +% cd llvm/projects +% svn co http://llvm.org/svn/llvm-project/test-suite/trunk llvm-test+
By placing it in the llvm/projects, it will be automatically configured by the LLVM configure script as well as automatically updated when you run svn update.
If you would like to get the GCC front end source code, you can also get it -and build it yourself. Please follow these +and build it yourself. Please follow these instructions to successfully get and build the LLVM GCC front-end.
@@ -745,7 +762,7 @@ instructions to successfully get and build the LLVM GCC front-end.Before configuring and compiling the LLVM suite, you can optionally extract the LLVM GCC front end from the binary distribution. It is used for running the llvm-test testsuite and for compiling C/C++ programs. Note that you can optionally -build llvm-gcc yourself after building the +build llvm-gcc yourself after building the main LLVM repository.
To install the GCC front end, do the following:
@@ -770,7 +787,7 @@ file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with libraries not available on your system.In cases like these, you may want to try building the GCC front end from source. This is +href="GCCFEBuildInstrs.html">building the GCC front end from source. This is much easier now than it was in the past.
@@ -825,7 +842,7 @@ script to configure the build system: will fail as these libraries require llvm-gcc and llvm-g++. See Install the GCC Front End for details on installing the C/C++ Front End. See - Bootstrapping the LLVM C/C++ Front-End + Bootstrapping the LLVM C/C++ Front-End for details on building the C/C++ Front End.To configure LLVM, follow these steps:
Change directory into the object root directory:
-% cd OBJ_ROOT
Run the configure script located in the LLVM source + tree:
+ +% SRC_ROOT/configure --prefix=/install/path [other options]+
Once you have LLVM configured, you can build it by entering the OBJ_ROOT directory and issuing the following command:
-gmake
+% gmake
If the build fails, please check here to see if you are using a version of GCC that is known not to compile LLVM.
@@ -943,7 +961,7 @@ If you have multiple processors in your machine, you may wish to use some of the parallel build options provided by GNU Make. For example, you could use the command: -gmake -j2
+% gmake -j2
There are several special targets which are useful when working with the LLVM source code:
@@ -973,8 +991,8 @@ source code:Change directory to where the LLVM object files should live:
-cd OBJ_ROOT
% cd OBJ_ROOT
Run the configure script found in the LLVM source directory:
-SRC_ROOT/configure
% SRC_ROOT/configure
The LLVM build will place files underneath OBJ_ROOT in directories @@ -1134,23 +1152,22 @@ named after the build type:
If you're running on a Linux system that supports the " - binfmt_misc" +href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc" module, and you have root access on the system, you can set your system up to -execute LLVM bytecode files directly. To do this, use commands like this (the +execute LLVM bitcode files directly. To do this, use commands like this (the first command may not be required if you are already using the module):
- $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc - $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register - $ chmod u+x hello.bc (if needed) - $ ./hello.bc +$ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc +$ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register +$ chmod u+x hello.bc (if needed) +$ ./hello.bc
-This allows you to execute LLVM bytecode files directly. Thanks to Jack +This allows you to execute LLVM bitcode files directly. Thanks to Jack Cummings for pointing this out!
@@ -1224,8 +1241,8 @@ different tools.This directory contains libraries which are compiled into LLVM bytecode and +
This directory contains libraries which are compiled into LLVM bitcode and used when linking programs with the GCC front end. Most of these libraries are skeleton versions of real libraries; for example, libc is a stripped down version of glibc.
@@ -1341,22 +1358,22 @@ information is in the Command Guide. be configured to utilize both LLVM and non-LLVM compilation tools to enable pre-processing, translation, optimization, assembly, and linking of programs all from one command line. llvmc also takes care of processing the - dependent libraries found in bytecode. This reduces the need to get the + dependent libraries found in bitcode. This reduces the need to get the traditional -l<name> options right on the command line. Please note that this tool, while functional, is still experimental and not feature complete.Note: The gcc4 frontend's invocation is considerably different from the previous gcc3 frontend. In particular, the gcc4 frontend does not -create bytecode by default: gcc4 produces native code. As the example below illustrates, -the '--emit-llvm' flag is needed to produce LLVM bytecode output. For makefiles and -configure scripts, the CFLAGS variable needs '--emit-llvm' to produce bytecode +create bitcode by default: gcc4 produces native code. As the example below illustrates, +the '--emit-llvm' flag is needed to produce LLVM bitcode output. For makefiles and +configure scripts, the CFLAGS variable needs '--emit-llvm' to produce bitcode output.
@@ -1501,41 +1515,46 @@ output.
- #include <stdio.h>
- int main() {
- printf("hello world\n");
- return 0;
- }
- First, create a simple C file, name it 'hello.c':
+ +
+#include <stdio.h>
+
+int main() {
+ printf("hello world\n");
+ return 0;
+}
+Next, compile the C file into a native executable:
-% llvm-gcc hello.c -o hello
+% llvm-gcc hello.c -o hello
Note that llvm-gcc works just like GCC by default. The standard -S and -c arguments work as usual (producing a native .s or .o file, - respectively).
+ respectively).Next, compile the C file into a LLVM bitcode file:
-Next, compile the C file into a LLVM bytecode file:
-% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc
+% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc
The -emit-llvm option can be used with the -S or -c options to emit an LLVM ".ll" or ".bc" file (respectively) for the code. This allows you to use the standard LLVM tools on - the bytecode file.
+ the bitcode file.Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
Run the program in both forms. To run the program, use:
-% ./hello
+% ./hello
and
-% lli hello.bc
+% lli hello.bc
The second examples shows how to invoke the LLVM JIT, lli.
Use the llvm-dis utility to take a look at the LLVM assembly code:
-% llvm-dis < hello.bc | less
llvm-dis < hello.bc | less+
Compile the program to native assembly using the LLC code generator:
-% llc hello.bc -o hello.s
+% llc hello.bc -o hello.s
Assemble the native assembly language file into a program:
-Solaris:% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
-Others:% gcc hello.s -o hello.native
++Solaris: % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native + +Others: % gcc hello.s -o hello.native ++
Execute the native code program:
-% ./hello.native
+% ./hello.native
Note that using llvm-gcc to compile directly to native code (i.e. when the -emit-llvm option is not present) does steps 6/7/8 for you.