LLVM is very demanding of the host C++ compiler, and as such tends to expose
bugs in the compiler. In particular, several versions of GCC crash when trying
-to compile LLVM. We routinely use GCC 3.3.3 and GCC 3.4.0 and have had success
-with them. Other versions of GCC will probably work as well. GCC versions listed
+to compile LLVM. We routinely use GCC 3.3.3, 3.4.0, and Apple 4.0.1
+successfully with them (however, see below). Other versions of GCC will
+probably work as well. GCC versions listed
here are known to not work. If you are using one of these versions, please try
to upgrade your GCC to something more recent. If you run into a problem with a
version of GCC not listed here, please let
@@ -450,10 +512,40 @@ of GCC you are using.
problems in the STL that effectively prevent it from compiling LLVM.
+
- This is the where the LLVM GCC Front End is installed.
+ This is where the LLVM GCC Front End is installed.
For the pre-built GCC front end binaries, the LLVMGCCDIR is
- cfrontend/platform/llvm-gcc.
+ llvm-gcc/platform/llvm-gcc.
@@ -521,23 +613,17 @@ All these paths are absolute:
-In order to compile and use LLVM, you will need to set some environment
-variables. There are also some shell aliases which you may find useful.
-You can set these on the command line, or better yet, set them in your
-.cshrc or .profile.
+In order to compile and use LLVM, you may need to set some environment
+variables.
- - LLVM_LIB_SEARCH_PATH=LLVMGCCDIR/bytecode-libs
-
-
- This environment variable helps the LLVM GCC front end find bytecode
- libraries that it will need for compilation.
-
-
-
- alias llvmgcc LLVMGCCDIR/bin/gcc
-
- alias llvmg++ LLVMGCCDIR/bin/g++
-
-
- This alias allows you to use the LLVM C and C++ front ends without putting
- them in your PATH or typing in their complete pathnames.
+
- LLVM_LIB_SEARCH_PATH=/path/to/your/bytecode/libs
+ - [Optional] This environment variable helps LLVM linking tools find the
+ locations of your bytecode libraries. It is provided only as a
+ convenience since you can specify the paths using the -L options of the
+ tools and the C/C++ front-end will automatically use the bytecode files
+ installed in its
+ lib directory.
@@ -552,32 +638,32 @@ You can set these on the command line, or better yet, set them in your
If you have the LLVM distribution, you will need to unpack it before you
can begin to compile it. LLVM is distributed as a set of two files: the LLVM
-suite and the LLVM GCC front end compiled for your platform. Each
-file is a TAR archive that is compressed with the gzip program.
+suite and the LLVM GCC front end compiled for your platform. There is an
+additional test suite that is optional. Each file is a TAR archive that is
+compressed with the gzip program.
- The files are as follows:
+
The files are as follows, with x.y marking the version number:
- - llvm-1.3.tar.gz
-
- This is the source code to the LLVM suite.
-
+
- llvm-x.y.tar.gz
+ - Source release for the LLVM libraries and tools.
- - cfrontend-1.3.sparc-sun-solaris2.8.tar.gz
-
- This is the binary release of the GCC front end for Solaris/Sparc.
-
+
- llvm-test-x.y.tar.gz
+ - Source release for the LLVM test suite.
- - cfrontend-1.3.i686-redhat-linux-gnu.tar.gz
-
- This is the binary release of the GCC front end for Linux/x86.
-
+
- llvm-gcc4-x.y.source.tar.gz
+ - Source release of the llvm-gcc4 front end. See README.LLVM in the root
+ directory for build instructions.
- - cfrontend-1.3.i386-unknown-freebsd5.1.tar.gz
-
- This is the binary release of the GCC front end for FreeBSD/x86.
-
+
- llvm-gcc4-x.y-platform.tar.gz
+ - Binary release of the llvm-gcc4 front end for a specific platform.
- - cfrontend-1.3.powerpc-apple-darwin7.0.0.tar.gz
-
- This is the binary release of the GCC front end for MacOS X/PPC.
+It is also possible to download the sources of the llvm-gcc4 front end from a
+read-only subversion mirror at
+svn://anonsvn.opensource.apple.com/svn/llvm/trunk.
+
@@ -593,9 +679,9 @@ follows:
- cd where-you-want-llvm-to-live
-
- cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login
+
- cvs -d :pserver:anon@llvm.org:/var/cvs/llvm login
- Hit the return key when prompted for the password.
-
- cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
+
- cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co
llvm
@@ -605,41 +691,35 @@ test directories, and local copies of documentation files.
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
-label:
+labels:
+- Release 1.9: RELEASE_19
+- Release 1.8: RELEASE_18
+- Release 1.7: RELEASE_17
+- Release 1.6: RELEASE_16
+- Release 1.5: RELEASE_15
+- Release 1.4: RELEASE_14
- Release 1.3: RELEASE_13
- Release 1.2: RELEASE_12
- Release 1.1: RELEASE_11
- Release 1.0: RELEASE_1
-If you would like to get the GCC front end source code, you can also get it
-from the CVS repository:
-
+If you would like to get the LLVM test suite (a separate package as of 1.4),
+you get it from the CVS repository:
- cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
+ cd llvm/projects
+ cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co 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 cvs update.
-Please note that you must follow these
-instructions to successfully build the LLVM C front-end.
-
-
+If you would like to get the GCC front end source code, you can also get it
+and build it yourself. Please follow these
+instructions to successfully get and build the LLVM GCC front-end.
-
-
-
-
-
-
If the main CVS server is overloaded or inaccessible, you can try one of
-these user-hosted mirrors:
-
-
-
Before configuring and compiling the LLVM suite, you need to extract the LLVM
-GCC front end from the binary distribution. It is used for building the
-bytecode libraries later used by the GCC front end for linking programs, and its
-location must be specified when the LLVM suite is configured.
+
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
+main LLVM repository.
To install the GCC front end, do the following:
- cd where-you-want-the-front-end-to-live
- - gunzip --stdout cfrontend-version.platform.tar.gz | tar -xvf
+
- gunzip --stdout llvmgcc-version.platform.tar.gz | tar -xvf
-
-
If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
-header files:
-
-
cd cfrontend/platform
- ./fixheaders
+
Once the binary is uncompressed, you should add a symlink for llvm-gcc and
+llvm-g++ to some directory in your path. When you configure LLVM, it will
+automatically detect llvm-gcc's presence (if it is in your path) enabling its
+use in llvm-test. Note that you can always build or install llvm-gcc at any
+pointer after building the main LLVM repository: just reconfigure llvm and
+llvm-test will pick it up.
+
The binary versions of the GCC front end may not suit all of your needs. For
example, the binary distribution may include an old version of a system header
@@ -675,7 +758,7 @@ 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
-not for the faint of heart, so be forewarned.
+much easier now than it was in the past.
Once checked out from the CVS repository, the LLVM suite source code must be
-configured via the configure script. This script sets variables in
-llvm/Makefile.config and llvm/include/Config/config.h. It
-also populates OBJ_ROOT with the Makefiles needed to begin building
-LLVM.
+configured via the
configure script. This script sets variables in the
+various
*.in files, most notably
llvm/Makefile.config and
+
llvm/include/Config/config.h. It also populates
OBJ_ROOT with
+the Makefiles needed to begin building LLVM.
The following environment variables are used by the configure
script to configure the build system:
-
+
| Variable | Purpose |
|---|
| CC |
@@ -716,47 +799,69 @@ script to configure the build system:
The following options can be used to set or enable LLVM specific options:
- - --with-llvmgccdir=LLVMGCCDIR
-
-
- Path to the location where the LLVM GCC front end binaries and
- associated libraries were installed. This must be specified as an
- absolute pathname.
-
-
- --enable-optimized
+
- --with-llvmgccdir
+ - Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
+ The value of this option should specify the full pathname of the C/C++ Front
+ End to be used. If this option is not provided, the PATH will be searched for
+ a program named llvm-gcc and the C/C++ FrontEnd install directory will
+ be inferred from the path found. If the option is not given, and no llvm-gcc
+ can be found in the path then a warning will be produced by
+ configure indicating this situation. LLVM may still be built with
+ the tools-only target but attempting to build the runtime libraries
+ 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
+ for details on building the C/C++ Front End.
+ - --with-tclinclude
+ - Path to the tcl include directory under which tclsh can be
+ found. Use this if you have multiple tcl installations on your machine and you
+ want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
+ dejagnu based test suite in llvm/test. If you don't specify this
+ option, the LLVM configure script will search for the tcl 8.4 and 8.3
+ releases.
+
+
+ - --enable-optimized
-
Enables optimized compilation by default (debugging symbols are removed
and GCC optimization flags are enabled). The default is to use an
unoptimized build (also known as a debug build).
-
-
- --enable-jit
+
+
+ - --enable-debug-runtime
+ -
+ Enables debug symbols in the runtime libraries. The default is to strip
+ debug symbols from the runtime libraries.
+
+ - --enable-jit
-
Compile the Just In Time (JIT) compiler functionality. This is not
available
on all platforms. The default is dependent on platform, so it is best
to explicitly enable it if you want it.
-
-
- --enable-spec2000
-
- --enable-spec2000=<directory>
-
-
- Enable the use of SPEC2000 when testing LLVM. This is disabled by default
- (unless configure finds SPEC2000 installed). By specifying
- directory, you can tell configure where to find the SPEC2000
- benchmarks. If directory is left unspecified, configure
- uses the default value
- /home/vadve/shared/benchmarks/speccpu2000/benchspec.
-
-
- --enable-spec95
-
- --enable-spec95=<directory>
-
-
- Enable the use of SPEC95 when testing LLVM. It is similar to the
- --enable-spec2000 option.
-
-
- --enable-povray
-
- --enable-povray=<directory>
-
-
- Enable the use of Povray as an external test. Versions of Povray written
- in C should work. This option is similar to the --enable-spec2000
- option.
+
+
+ - --enable-targets=target-option
+ - Controls which targets will be built and linked into llc. The default
+ value for target_options is "all" which builds and links all
+ available targets. The value "host-only" can be specified to build only a
+ native compiler (no cross-compiler targets available). The "native" target is
+ selected as the target of the build host. You can also specify a comma
+ separated list of target names that you want available in llc. The target
+ names use all lower case. The current set of targets is:
+ alpha, ia64, powerpc, skeleton, sparc, x86.
+
+ - --enable-doxygen
+ - Look for the doxygen program and enable construction of doxygen based
+ documentation from the source code. This is disabled by default because
+ generating the documentation can take a long time and producess 100s of
+ megabytes of output.
+ - --with-udis86
+ - LLVM can use external disassembler library for various purposes (now it's
+ used only for examining code produced by JIT). This option will enable usage
+ of udis86 x86 (both 32 and 64
+ bits) disassembler library.
To configure LLVM, follow these steps:
@@ -765,24 +870,14 @@ script to configure the build system:
Change directory into the object root directory:
cd OBJ_ROOT
-
+
Run the configure script located in the LLVM source tree:
- SRC_ROOT/configure
-
+ SRC_ROOT/configure --prefix=/install/path [other options]
+
-
In addition to running configure, you must set the
-LLVM_LIB_SEARCH_PATH environment variable in your startup scripts.
-This environment variable is used to locate "system" libraries like
-"-lc" and "-lm" when linking. This variable should be set to
-the absolute path of the bytecode-libs subdirectory of the GCC front
-end, or LLVMGCCDIR/bytecode-libs. For example, one might set
-LLVM_LIB_SEARCH_PATH to
-/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs for the x86
-version of the GCC front end on our research machines.
-
@@ -802,7 +897,7 @@ builds:
--enable-optimized option was used during configuration). The
build system will compile the tools and libraries with debugging
information.
-
+
Release (Optimized) Builds
@@ -811,7 +906,7 @@ builds:
gmake command line. For these builds, the build system will
compile the tools and libraries with GCC optimizations enabled and strip
debugging information from the libraries and executables it generates.
-
+
Profile Builds
@@ -827,7 +922,7 @@ builds:
gmake
If the build fails, please check here to see if you
-are using a known broken version of GCC to compile LLVM with.
+are using a version of GCC that is known not to compile LLVM.
If you have multiple processors in your machine, you may wish to use some of
@@ -844,30 +939,36 @@ source code:
Removes all files generated by the build. This includes object files,
generated C/C++ files, libraries, and executables.
-
+
-
gmake distclean
+ gmake dist-clean
Removes everything that gmake clean does, but also removes files
generated by configure. It attempts to return the source tree to the
original state in which it was shipped.
-
+
gmake install
- Installs LLVM libraries and tools in a heirarchy under $PREFIX, specified with
- ./configure --prefix=[dir], defaults to /usr/local.
-
-
-
gmake -C runtime install
+ Installs LLVM header files, libraries, tools, and documentation in a
+ hierarchy
+ under $PREFIX, specified with ./configure --prefix=[dir], which
+ defaults to /usr/local.
+
+
+ gmake -C runtime install-bytecode
Assuming you built LLVM into $OBJDIR, when this command is run, it will
install bytecode libraries into the GCC front end's bytecode library
directory. If you need to update your bytecode libraries,
this is the target to use once you've built them.
-
+
+
Please see the Makefile Guide for further
+details on these make targets and descriptions of other targets
+available.
+
It is also possible to override default values from configure by
declaring variables on the command line. The following are some examples:
@@ -875,17 +976,27 @@ declaring variables on the command line. The following are some examples:
gmake ENABLE_OPTIMIZED=1
Perform a Release (Optimized) build.
-
+
+
+
gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1
+
+ Perform a Release (Optimized) build without assertions enabled.
+
gmake ENABLE_PROFILING=1
Perform a Profiling build.
-
+
gmake VERBOSE=1
Print what gmake is doing on standard output.
-
+
+
+
gmake TOOL_VERBOSE=1
+ Ask each tool invoked by the makefiles to print out what it is doing on
+ the standard output. This also implies VERBOSE=1.
+
Every directory in the LLVM object tree includes a Makefile to build
@@ -895,6 +1006,51 @@ that directory that is out of date.
+
+
+
+
+
It is possible to cross-compile LLVM. That is, you can create LLVM
+ executables and libraries for a platform different than the one one which you
+ are compiling. To do this, a few additional steps are
+ required. 1 To cross-compile LLVM, use
+ these instructions:
+
+ - Configure and build LLVM as a native compiler. You will need
+ just TableGen from that build.
+
+ - If you have $LLVM_OBJ_ROOT=$LLVM_SRC_ROOT just execute
+ make -C utils/TableGen after configuring.
+ - Otherwise you will need to monitor building process and terminate
+ it just after TableGen was built.
+
+
+ - Copy the TableGen binary to somewhere safe (out of your build tree).
+
+ - Configure LLVM to build with a cross-compiler. To do this, supply the
+ configure script with --build and --host options that
+ are different. The values of these options must be legal target triples
+ that your GCC compiler supports.
+ - Put the saved TableGen executable into the
+ into $LLVM_OBJ_ROOT/{BUILD_TYPE}/bin directory (e.g. into
+ .../Release/bin for a Release build).
+ - Build LLVM as usual.
+
+
The result of such a build will produce executables that are not executable
+ on your build host (--build option) but can be executed on your compile host
+ (--host option).
+
Notes:
+
+
+ - Cross-compiling was tested only with Linux as
+ build platform and Windows as host using mingw32 cross-compiler. Other
+ combinations have not been tested.
+
+
+
The Location of LLVM Object Files
@@ -927,29 +1083,29 @@ named after the build type:
- Tools
-
- OBJ_ROOT/tools/Debug
+
- OBJ_ROOT/Debug/bin
- Libraries
-
- OBJ_ROOT/lib/Debug
+
- OBJ_ROOT/Debug/lib
-
+
Release Builds
- Tools
-
- OBJ_ROOT/tools/Release
+
- OBJ_ROOT/Release/bin
- Libraries
-
- OBJ_ROOT/lib/Release
+
- OBJ_ROOT/Release/lib
-
+
Profile Builds
- Tools
-
- OBJ_ROOT/tools/Profile
+
- OBJ_ROOT/Profile/bin
- Libraries
-
- OBJ_ROOT/lib/Profile
+
- OBJ_ROOT/Profile/lib
@@ -963,18 +1119,21 @@ named after the build type:
-If you're running on a linux system that supports the "binfmt_misc"
+If you're running on a Linux system that supports the "
+ 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
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
+ $ 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
@@ -994,24 +1153,27 @@ Cummings for pointing this out!
One useful source of information about the LLVM source base is the LLVM doxygen documentation available at http://llvm.cs.uiuc.edu/doxygen/.
+href="http://llvm.org/doxygen/">http://llvm.org/doxygen/.
The following is a brief introduction to code layout:
-
-
Every directory checked out of CVS will contain a CVS directory; for
the most part these can just be ignored.
+
+
This directory contains some simple examples of how to use the LLVM IR and
+ JIT.
This directory contains public header files exported from the LLVM
@@ -1040,7 +1202,6 @@ library. The three main subdirectories of this directory are:
-
This directory contains most of the source files of the LLVM system. In LLVM,
@@ -1072,9 +1233,9 @@ different tools.
llvm/lib/Target/
This directory contains files that describe various target architectures
- for code generation. For example, the llvm/lib/Target/SparcV9
- directory holds the Sparc machine description while
- llvm/lib/Target/CBackend implements the LLVM-to-C converter
+ for code generation. For example, the
llvm/lib/Target/X86
+ directory holds the X86 machine description while
+
llvm/lib/Target/CBackend implements the LLVM-to-C converter.
llvm/lib/CodeGen/
This directory contains the major parts of the code generator: Instruction
@@ -1100,6 +1261,16 @@ different tools.
+
+
+
+
This directory contains projects that are not strictly part of LLVM but are
+ shipped with LLVM. This is also the directory where you should create your own
+ LLVM-based projects. See llvm/projects/sample for an example of how
+ to set up your own project. See llvm/projects/Stacker for a fully
+ functional example of a compiler front end.
+
+
@@ -1125,12 +1296,13 @@ end to compile.
-
This is not a directory in the normal llvm module, it is a separate CVS
- module that must be checked out (usually to test/projects). This
- module contains a comprehensive correctness, performance and benchmarking test
+
This is not a directory in the normal llvm module; it is a separate CVS
+ module that must be checked out (usually to projects/llvm-test). This
+ module contains a comprehensive correctness, performance, and benchmarking
+ test
suite for LLVM. It is a separate CVS module because not every LLVM user is
- interested in downloading or building such a comprehensive test. For further
- details on this test suite, please see the
+ interested in downloading or building such a comprehensive test suite. For
+ further details on this test suite, please see the
Testing Guide document.
@@ -1141,14 +1313,10 @@ end to compile.
The tools directory contains the executables built out of the
libraries above, which form the main part of the user interface. You can
always get help for a tool by typing tool_name --help. The
-following is a brief introduction to the most important tools:
+following is a brief introduction to the most important tools. More detailed
+information is in the
Command Guide.
- - analyze
- - analyze is used to run a specific
- analysis on an input LLVM bytecode file and print out the results. It is
- primarily useful for debugging analyses, or familiarizing yourself with
- what an analysis does.
- bugpoint
- bugpoint is used to debug
@@ -1164,7 +1332,9 @@ following is a brief introduction to the most important tools:
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
- traditional -l<name> options right on the command line.
+ traditional -l<name> options right on the command line. Please
+ note that this tool, while functional, is still experimental and not feature
+ complete.
- llvm-ar
- The archiver produces an archive containing
@@ -1179,6 +1349,12 @@ following is a brief introduction to the most important tools:
- The disassembler transforms the LLVM bytecode to human readable
LLVM assembly.
+ - llvm-ld
+ - llvm-ld is a general purpose and extensible linker for LLVM.
+ This is the linker invoked by llvmc. It performsn standard link time
+ optimizations and allows optimization modules to be loaded and run so that
+ language specific optimizations can be applied at link time.
+
- llvm-link
- llvm-link, not surprisingly, links multiple LLVM modules into
a single program.
@@ -1188,55 +1364,33 @@ following is a brief introduction to the most important tools:
can directly execute LLVM bytecode (although very slowly...). In addition
to a simple interpreter, lli also has a tracing mode (entered by
specifying -trace on the command line). Finally, for
- architectures that support it (currently only x86 and Sparc), by default,
+ architectures that support it (currently x86, Sparc, and PowerPC), by default,
lli will function as a Just-In-Time compiler (if the
functionality was compiled in), and will execute the code much
faster than the interpreter.
- llc
- llc is the LLVM backend compiler, which
- translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
+ translates LLVM bytecode to a native code assembly file or to C code (with
the -march=c option).
- - llvmgcc
- - llvmgcc is a GCC-based C frontend
- that has been retargeted to emit LLVM code as the machine code output. It
- works just like any other GCC compiler, taking the typical -c, -S, -E,
- -o options that are typically used. The source code for the
- llvmgcc tool is currently not included in the LLVM CVS tree
- because it is quite large and not very interesting.
-
-
- - gccas
- - This tool is invoked by the llvmgcc frontend as the
- "assembler" part of the compiler. This tool actually assembles LLVM
- assembly to LLVM bytecode, performs a variety of optimizations, and
- outputs LLVM bytecode. Thus when you invoke
- llvmgcc -c x.c -o x.o, you are causing gccas to be
- run, which writes the x.o file (which is an LLVM bytecode file
- that can be disassembled or manipulated just like any other bytecode
- file). The command line interface to gccas is designed to be
- as close as possible to the system `as' utility so that
- the gcc frontend itself did not have to be modified to interface to
- a "weird" assembler.
-
- - gccld
- - gccld links together several LLVM bytecode files into one
- bytecode file and does some optimization. It is the linker invoked by
- the GCC frontend when multiple .o files need to be linked together.
- Like gccas, the command line interface of gccld is
- designed to match the system linker, to aid interfacing with the GCC
- frontend.
-
-
-
+ - llvm-gcc
+ - llvm-gcc is a GCC-based C frontend that has been retargeted to
+ use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
+ byte code or assembly (with the -emit-llvm option) instead of the
+ usual machine code output. It works just like any other GCC compiler,
+ taking the typical -c, -S, -E, -o options that are typically used.
+ Additionally, the the source code for llvm-gcc is available as a
+ separate CVS module.
- opt
- - opt reads LLVM bytecode, applies a
- series of LLVM to LLVM transformations (which are specified on the command
- line), and then outputs the resultant bytecode. The 'opt --help'
- command is a good way to get a list of the program transformations
- available in LLVM.
+ - opt reads LLVM bytecode, applies a series of LLVM to LLVM
+ transformations (which are specified on the command line), and then outputs
+ the resultant bytecode. The 'opt --help' command is a good way to
+ get a list of the program transformations available in LLVM.
+ - opt can also be used to run a specific analysis on an input
+ LLVM bytecode file and print out the results. It is primarily useful for
+ debugging analyses, or familiarizing yourself with what an analysis does.
@@ -1249,16 +1403,11 @@ of the utilities are actually required as part of the build process because they
are code generators for parts of LLVM infrastructure.
- - Burg/
- Burg is an instruction selector
- generator -- it builds trees on which it then performs pattern-matching to
- select instructions according to the patterns the user has specified. Burg
- is currently used in the Sparc V9 backend.
-
- codegen-diff
- codegen-diff is a script
that finds differences between code that LLC generates and code that LLI
generates. This is a useful tool if you are debugging one of them,
assuming that the other generates correct output. For the full user
- manual, run `perldoc codegen-diff'.
+ manual, run `perldoc codegen-diff'.
- cvsupdate
- cvsupdate is a script that will
update your CVS tree, but produce a much cleaner and more organized output
@@ -1266,21 +1415,21 @@ are code generators for parts of LLVM infrastructure.
together all the new and updated files and modified files in separate
sections, so you can see at a glance what has changed. If you are at the
top of your LLVM CVS tree, running utils/cvsupdate is the
- preferred way of updating the tree.
+ preferred way of updating the tree.
- emacs/
- The emacs directory contains
syntax-highlighting files which will work with Emacs and XEmacs editors,
providing syntax highlighting support for LLVM assembly files and TableGen
description files. For information on how to use the syntax files, consult
- the README file in that directory.
+ the README file in that directory.
- getsrcs.sh
- The getsrcs.sh script finds
and outputs all non-generated source files, which is useful if one wishes
to do a lot of development across directories and does not want to
individually find each file. One way to use it is to run, for example:
xemacs `utils/getsources.sh` from the top of your LLVM source
- tree.
-
+ tree.
+
- llvmgrep
- This little tool performs an "egrep -H -n" on each source file in LLVM and
passes to it a regular expression provided on llvmgrep's command
@@ -1293,35 +1442,60 @@ are code generators for parts of LLVM infrastructure.
llvm/lib/Target/Sparc, if makellvm is in your path,
simply running makellvm llc will make a build of the current
directory, switch to directory llvm/tools/llc and build it,
- causing a re-linking of LLC.
+ causing a re-linking of LLC.
- NightlyTest.pl and
NightlyTestTemplate.html
- These files are used in a
cron script to generate nightly status reports of the functionality of
tools, and the results can be seen by following the appropriate link on
- the LLVM homepage.
+ the LLVM homepage.
- TableGen/
- The TableGen directory contains
the tool used to generate register descriptions, instruction set
descriptions, and even assemblers from common TableGen description
- files.
+ files.
- vim/
- The vim directory contains
syntax-highlighting files which will work with the VIM editor, providing
syntax highlighting support for LLVM assembly files and TableGen
description files. For information on how to use the syntax files, consult
- the README file in that directory.
+ the README file in that directory.
+
+
+
+
This directory contains build scripts and project files for use with
+ Visual C++. This allows developers on Windows to build LLVM without the need
+ for Cygwin. The contents of this directory should be considered experimental
+ at this time.
+
+
+
This section gives an example of using LLVM. llvm-gcc3 is now obsolete,
+so we only include instructiosn for llvm-gcc4.
+
+
+
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
+output.
+
@@ -1334,33 +1508,40 @@ are code generators for parts of LLVM infrastructure.
}
+ Next, compile the C file into a native executable:
+
+ % 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).
+
Next, compile the C file into a LLVM bytecode file:
- % llvmgcc hello.c -o hello
+ % llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc
- Note that you should have already built the tools and they have to be
- in your path, at least gccas and gccld.
+ 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.
- This will create two result files: hello and
- hello.bc. The hello.bc is the LLVM bytecode that
- corresponds the the compiled program and the library facilities that it
- required. hello is a simple shell script that runs the bytecode
- file with lli, making the result directly executable. Note that
- all LLVM optimizations are enabled by default, so there is no need for a
- "-O3" switch.
Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
+
- Run the program. To make sure the program ran, execute one of the
- following commands:
+ Run the program in both forms. To run the program, use:
% ./hello
- or
+ 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:
@@ -1374,12 +1555,17 @@ are code generators for parts of LLVM infrastructure.
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.
+
+