Some porting problems may exist in the following areas:
I compile the code, and I get some error about /localhome.
-There are several possible causes for this. The first is that you didn't set -a pathname properly when using configure, and it defaulted to a -pathname that we use on our research machines.
- -Another possibility is that we hardcoded a path in our Makefiles. If you see -this, please email the LLVM bug mailing list with the name of the offending -Makefile and a description of what is wrong with it.
- -The configure script finds the right C compiler, but it uses the LLVM linker from a previous build. What do I do?
@@ -238,21 +226,23 @@ if it's grabbing the wrong linker/assembler/etc, there are two ways to fix it:Adjust your PATH environment variable so that the correct - program appears first in the PATH. This may work, but may not be - convenient when you want them first in your path for other - work.
Run configure with an alternative PATH that is - correct. In a Borne compatible shell, the syntax would be:
- -PATH=[the path without the bad program] ./configure ...
+ correct. In a Borne compatible shell, the syntax would be: + ++% PATH=[the path without the bad program] ./configure ... ++
This is still somewhat inconvenient, but it allows configure - to do its work without having to adjust your PATH - permanently.
I've updated my source tree from CVS, and now my build is trying to use a -file/directory that doesn't exist.
+I've updated my source tree from Subversion, and now my build is trying to +use a file/directory that doesn't exist.
If the Makefile already exists in your object tree, you can just run the following command in the top level directory of your object tree:
-./config.status <relative path to Makefile>
+
% ./config.status <relative path to Makefile>+
If the Makefile is new, you will have to modify the configure script to copy it over.
@@ -324,11 +315,18 @@ clean and then make in the directory that fails to build.For example, if you built LLVM with the command:
-gmake ENABLE_PROFILING=1 +
% gmake ENABLE_PROFILING=1+
...then you must run the tests with the following commands:
-cd llvm/test
gmake ENABLE_PROFILING=1
+% cd llvm/test +% gmake ENABLE_PROFILING=1 ++
This is a bug in GCC, and - affects projects other than LLVM. Try upgrading or downgrading your GCC.
+affects projects other than LLVM. Try upgrading or downgrading your GCC.After CVS update, rebuilding gives the error "No rule to make target".
+After Subversion update, rebuilding gives the error "No rule to make +target".
If the error is of the form:
gmake[2]: *** No rule to make target `/path/to/somefile', needed by `/path/to/another/file.d'.+
Stop. -
This may occur anytime files are moved within the CVS repository or removed -entirely. In this case, the best solution is to erase all .d files, -which list dependencies for source files, and rebuild:
+This may occur anytime files are moved within the Subversion repository or +removed entirely. In this case, the best solution is to erase all +.d files, which list dependencies for source files, and rebuild:
@@ -390,6 +389,15 @@ which list dependencies for source files, and rebuild: rebuilding.
llvmc is experimental and isn't really supported. We suggest +using llvm-gcc instead.
+There is an incomplete version of a Java front end available in the - llvm-java CVS repository. There is no documentation on this yet so + java module. There is no documentation on this yet so you'll need to download the code, compile it, and try it.
-In the examples/BFtoLLVM directory is a translator for the - BrainF*** language (2002 Language Specification).
-In the projects/Stacker directory is a compiler and runtime +
In the stacker module is a compiler and runtime library for the Stacker language, a "toy" language loosely based on Forth.
The PyPy developers are working on integrating LLVM into the PyPy backend so that PyPy language can translate to LLVM.
What support is there for a higher level source language constructs for + +
+Your compiler front-end will communicate with LLVM by creating a module in + the LLVM intermediate representation (IR) format. Assuming you want to + write your language's compiler in the language itself (rather than C++), + there are 3 major ways to tackle generating LLVM IR from a front-end:
+If you go with the first option, the C bindings in include/llvm-c should + help a lot, since most languages have strong support for interfacing with + C. The most common hurdle with calling C from managed code is interfacing + with the garbage collector. The C interface was designed to require very + little memory management, and so is straightforward in this regard.
+To work around this, perform the following steps:
--This will allow the gccld linker to create a native code executable instead of -a shell script that runs the JIT. Creating native code requires standard -linkage, which in turn will allow the configure script to find out if code is -not linking on your system because the feature isn't available on your system. -
+This will allow the llvm-ld linker to create a native code executable +instead of shell script that runs the JIT. Creating native code requires +standard linkage, which in turn will allow the configure script to find out if +code is not linking on your system because the feature isn't available on your +system.The only way this can happen is if you haven't installed the runtime library. To correct this, do:
+ +- % cd llvm/runtime - % make clean ; make install-bytecode +% cd llvm/runtime +% make clean ; make install-bytecode
@@ -501,33 +564,85 @@ code that you desire.
-The __main call is inserted by the C/C++ compiler in order to guarantee -that static constructors and destructors are called when the program starts up -and shuts down. In C, you can create static constructors and destructors by -using GCC extensions, and in C++ you can do so by creating a global variable -whose class has a ctor or dtor. +Can I use LLVM to convert C++ code to C code?
+-The actual implementation of __main lives in the -llvm/runtime/GCCLibraries/crtend/ directory in the source-base, and is -linked in automatically when you link the program. +
Yes, you can use LLVM to convert code from any language LLVM supports to C. +Note that the generated C code will be very low level (all loops are lowered +to gotos, etc) and not very pretty (comments are stripped, original source +formatting is totally lost, variables are renamed, expressions are regrouped), +so this may not be what you're looking for. However, this is a good way to add +C++ support for a processor that does not otherwise have a C++ compiler.
+ +Use commands like this:
+ +Compile your program as normal with llvm-g++:
+ ++% llvm-g++ x.cpp -o program +
or:
+ ++% llvm-g++ a.cpp -c +% llvm-g++ b.cpp -c +% llvm-g++ a.o b.o -o program ++
With llvm-gcc3, this will generate program and program.bc. The .bc + file is the LLVM version of the program all linked together.
Convert the LLVM code to C code, using the LLC tool with the C + backend:
+ ++% llc -march=c program.bc -o program.c ++
Finally, compile the C file:
+ ++% cc x.c ++
Note that, by default, the C backend does not support exception handling. If +you want/need it for a certain program, you can enable it by passing +"-enable-correct-eh-support" to the llc program. The resultant code will use +setjmp/longjmp to implement exception support that is correct but relatively +slow.
+ +Also note: this specific sequence of commands won't work if you use a +function defined in the C++ runtime library (or any other C++ library). To +access an external C++ library, you must manually compile libstdc++ to LLVM +bitcode, statically link it into your program, then use the commands above to +convert the whole result into C code. Alternatively, you can compile the +libraries and your application into two different chunks of C code and link +them.
+ +
+int X() { int i; return i; }
+
Is compiled to "ret int undef" because "i" never has a value -specified for it. -
+Is compiled to "ret i32 undef" because "i" never has +a value specified for it.