llvm dev - Jul 2010 - [LLVMdev] Is there a guide to LLVM's components?

One thing that helps me understand complex software is a dependency graph. I
found an LLVM dependency graph at

https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_16/docs/UsingLibraries.html#dependencies

but it's really messy and hard to follow. From that graph I made a cleaner
graph by hand (attached)... sorry about the fax-quality scan. But I have some
questions about it...


-          How old is this graph?

-          Is anything missing? (e.g. only SPARC stuff is present, I guess x86
et al would have similar dependencies?)

-          The web page says "Where a library has both archive and object
forms, only the archive form is shown." Are "archive library" and
"object library" the names Unix uses for dynamic link libraries and
static libraries? What difference does it make to the dependency graph whether a
library is "archive" or "object"?

From: David Piepgrass
Sent: Wednesday, July 21, 2010 4:16 PM
To: 'llvmdev at cs.uiuc.edu'
Subject: Is there a guide to LLVM's components?

I constructed an LLVM 2.7 VS solution with cmake, but it has 66 projects:

                ALL_BUILD, ".\ALL_BUILD.vcproj"
                BrainF, "examples\BrainF\BrainF.vcproj"
                Fibonacci, "examples\Fibonacci\Fibonacci.vcproj"
                FileCheck, "utils\FileCheck\FileCheck.vcproj"
                HowToUseJIT, "examples\HowToUseJIT\HowToUseJIT.vcproj"
                INSTALL, ".\INSTALL.vcproj"
                Kaleidoscope-Ch2,
"examples\Kaleidoscope\Chapter2\Kaleidoscope-Ch2.vcproj"
                Kaleidoscope-Ch3,
"examples\Kaleidoscope\Chapter3\Kaleidoscope-Ch3.vcproj"
                Kaleidoscope-Ch4,
"examples\Kaleidoscope\Chapter4\Kaleidoscope-Ch4.vcproj"
                Kaleidoscope-Ch5,
"examples\Kaleidoscope\Chapter5\Kaleidoscope-Ch5.vcproj"
                Kaleidoscope-Ch6,
"examples\Kaleidoscope\Chapter6\Kaleidoscope-Ch6.vcproj"
                Kaleidoscope-Ch7,
"examples\Kaleidoscope\Chapter7\Kaleidoscope-Ch7.vcproj"
                LLVMAnalysis, "lib\Analysis\LLVMAnalysis.vcproj"
                LLVMArchive, "lib\Archive\LLVMArchive.vcproj"
                LLVMAsmParser, "lib\AsmParser\LLVMAsmParser.vcproj"
                LLVMAsmPrinter,
"lib\CodeGen\AsmPrinter\LLVMAsmPrinter.vcproj"
                LLVMBitReader,
"lib\Bitcode\Reader\LLVMBitReader.vcproj"
                LLVMBitWriter,
"lib\Bitcode\Writer\LLVMBitWriter.vcproj"
                LLVMCodeGen, "lib\CodeGen\LLVMCodeGen.vcproj"
                LLVMCore, "lib\VMCore\LLVMCore.vcproj"
                LLVMExecutionEngine,
"lib\ExecutionEngine\LLVMExecutionEngine.vcproj"
                LLVMInstCombine,
"lib\Transforms\InstCombine\LLVMInstCombine.vcproj"
                LLVMInstrumentation,
"lib\Transforms\Instrumentation\LLVMInstrumentation.vcproj"
                LLVMInterpreter,
"lib\ExecutionEngine\Interpreter\LLVMInterpreter.vcproj"
                LLVMJIT, "lib\ExecutionEngine\JIT\LLVMJIT.vcproj"
                LLVMLinker, "lib\Linker\LLVMLinker.vcproj"
                LLVMMC, "lib\MC\LLVMMC.vcproj"
                LLVMMCParser, "lib\MC\MCParser\LLVMMCParser.vcproj"
                LLVMScalarOpts,
"lib\Transforms\Scalar\LLVMScalarOpts.vcproj"
                LLVMSelectionDAG,
"lib\CodeGen\SelectionDAG\LLVMSelectionDAG.vcproj"
                LLVMSupport, "lib\Support\LLVMSupport.vcproj"
                LLVMSystem, "lib\System\LLVMSystem.vcproj"
                LLVMTarget, "lib\Target\LLVMTarget.vcproj"
                LLVMTransformUtils,
"lib\Transforms\Utils\LLVMTransformUtils.vcproj"
                LLVMX86AsmParser,
"lib\Target\X86\AsmParser\LLVMX86AsmParser.vcproj"
                LLVMX86AsmPrinter,
"lib\Target\X86\AsmPrinter\LLVMX86AsmPrinter.vcproj"
                LLVMX86CodeGen, "lib\Target\X86\LLVMX86CodeGen.vcproj"
                LLVMX86Disassembler,
"lib\Target\X86\Disassembler\LLVMX86Disassembler.vcproj"
                LLVMX86Info,
"lib\Target\X86\TargetInfo\LLVMX86Info.vcproj"
                LLVMipa, "lib\Analysis\IPA\LLVMipa.vcproj"
                LLVMipo, "lib\Transforms\IPO\LLVMipo.vcproj"
                ModuleMaker, "examples\ModuleMaker\ModuleMaker.vcproj"
                X86CodeGenTable_gen,
"lib\Target\X86\X86CodeGenTable_gen.vcproj"
                ZERO_CHECK, ".\ZERO_CHECK.vcproj"
                bugpoint, "tools\bugpoint\bugpoint.vcproj"
                check, "test\check.vcproj"
                count, "utils\count\count.vcproj"
                intrinsics_gen, "include\llvm\intrinsics_gen.vcproj"
                llc, "tools\llc\llc.vcproj"
                lli, "tools\lli\lli.vcproj"
                llvm-ar, "tools\llvm-ar\llvm-ar.vcproj"
                llvm-as, "tools\llvm-as\llvm-as.vcproj"
                llvm-bcanalyzer,
"tools\llvm-bcanalyzer\llvm-bcanalyzer.vcproj"
                llvm-dis, "tools\llvm-dis\llvm-dis.vcproj"
                llvm-extract, "tools\llvm-extract\llvm-extract.vcproj"
                llvm-ld, "tools\llvm-ld\llvm-ld.vcproj"
                llvm-link, "tools\llvm-link\llvm-link.vcproj"
                llvm-mc, "tools\llvm-mc\llvm-mc.vcproj"
                llvm-nm, "tools\llvm-nm\llvm-nm.vcproj"
                llvm-prof, "tools\llvm-prof\llvm-prof.vcproj"
                llvm-ranlib, "tools\llvm-ranlib\llvm-ranlib.vcproj"
                llvm-stub, "tools\llvm-stub\llvm-stub.vcproj"
                llvm_headers_do_not_build,
"include\llvm\llvm_headers_do_not_build.vcproj"
                not, "utils\not\not.vcproj"
                opt, "tools\opt\opt.vcproj"
                tblgen, "utils\TableGen\tblgen.vcproj"

Is there a guide that explains the purpose of each? Obviously the ones in an
"example" folder are examples, but what about everything else? Is
there a guide to the LLVM components or source code?

If there are no such guides, could someone tell me which parts of LLVM are
needed for "minimal" JIT compilation? I would like to create small
amounts of IR at run-time, compile them in-memory, and run them. Basically I
would like to do as described at
http://www.codeproject.com/KB/cpp/runtime_compile.aspx, except that (in order to
minimize the code size), I would like to omit most/all optimizations.

Thanks,
David
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David Piepgrass <dpiepgrass at mentoreng.com> writes:
> One thing that helps me understand complex software is a dependency
> graph. I found an LLVM dependency graph at
>
>
https://llvm.org/svn/llvm-project/llvm/tags/RELEASE_16/docs/UsingLibraries.html#dependencies
>
> but it's really messy and hard to follow. From that graph I made a
> cleaner graph by hand (attached)... sorry about the fax-quality
> scan. But I have some questions about it...
>
>
> -          How old is this graph?
It is for the 1.6 release. Now we are at 2.7. So figure out.
> -          Is anything missing?
Sure.
> - The web page says "Where a library has both archive and object
> forms, only the archive form is shown." Are "archive
library" and
> "object library" the names Unix uses for dynamic link libraries
and
> static libraries? What difference does it make to the dependency graph
> whether a library is "archive" or "object"?
This is obsolete and never concerned to Visual Studio anyways.

If you are interested on dependency info look at
cmake/modules/LLVMLibDeps.cmake. It is not the prettiest thing to see,
but maybe you can get something from it.

> > I found an LLVM dependency graph at
> >
> > https://llvm.org/svn/llvm-
> project/llvm/tags/RELEASE_16/docs/UsingLibraries.html#dependencies
> >
> > but it's really messy and hard to follow. From that graph I made a
> > cleaner graph by hand (attached)... sorry about the fax-quality
> > scan. But I have some questions about it...
> >
> > -          How old is this graph?
> It is for the 1.6 release. Now we are at 2.7. So figure out.
> 
> > -          Is anything missing?
> Sure.
> 
> > - The web page says "Where a library has both archive and object
> > forms, only the archive form is shown." Are "archive
library" and
> > "object library" the names Unix uses for dynamic link
libraries and
> > static libraries? What difference does it make to the dependency
> graph whether a library is "archive" or "object"?
> This is obsolete and never concerned to Visual Studio anyways.
> 
> If you are interested on dependency info look at
> cmake/modules/LLVMLibDeps.cmake. It is not the prettiest thing to see,
> but maybe you can get something from it.
Well, I take it this means my manually-constructed graph is crap. Well, I
decided to try using automated tools such as graphvis and something called
"DepCharter" to construct a more up-to-date graph. Including all
targets on the graph produced a useless mess, so I removed most of the stuff
from "tools", "utils" and "examples" folders
(except HowToUseJIT) to produce another graph (attached).

But this graph raises some new questions, and I don't think it is
conceptually accurate.

- What is intrinsics_gen and why does pretty much everything depend on it?

- The graph says that nothing except HowToUseJIT depends on LLVMCore. In fact,
there are very few dependencies between different libraries.... for example,
unlike the earlier graph, it says LLVMAnalysis, LLVMTransformUtils and
LLVMScalarOpts DO NOT depend on each other. This is all wrong, right? I think
the problem is that it's a graph of BUILD dependencies, not real
dependencies: for example LLVMAnalysis and LLVMCore libraries can be BUILT
independently, because LLVMAnalysis' doesn't depend on LLVMCore until
link time. Therefore only executables, such as HowToUseJIT, actually needs to
list LLVMCore as a dependency. Yes?

I produced another graph by adapting cmake/modules/LLVMLibDeps.cmake to a
graphvis "dot" file, but the output is a useless rat's nest of
edges. I would need to somehow eliminate most of the "obvious" edges
to get something useful out of it...
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