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I have a ModulePass that's working with the opt tool, but I'm having trouble figuring out how to make it available to clang at the command line. My current workflow for using my pass is:
I would like to get my pass integrated with the clang command line so that it could be invoked as part of the build of existing software (e.g. c++ standard library) without having to remake the whole build system for each thing I compile. I've seen hints about how to do this, but I haven't been able to put the pieces together into a working setup.
Run an LLVM Pass Automatically with Clang describes exactly what I want, but the method appears to be deprecated in LLVM 3.4 (PassManagerBuilder has been moved to the legacy namespace).
LLVM - Run Own Pass automatically with clang seems to address the basic issue, but I was hoping I could do this without having to modify clang (which seems to be what's suggested there).
What is the best way to make a new pass available from clang using LLVM 3.4?
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Clang uses the LLVM compiler as its back end and it has been included in the release of the LLVM since the LLVM 2.6. Clang is also built to be a drop-in replacement for GCC command. In its design, the Clang compiler has been constructed to work very similarly to GCC to ensure that portability is maximized.
LLVM uses ID's address to identify a pass, so initialization value is not important. static RegisterPass<Hello> X("hello", "Hello World Pass", false /* Only looks at CFG */, false /* Analysis Pass */); Lastly, we register our class Hello , giving it a command line argument “ hello ”, and a name “Hello World Pass”.
LLVM is a backend compiler meant to build compilers on top of it. It deals with optimizations and production of code adapted to the target architecture. CLang is a front end which parses C, C++ and Objective C code and translates it into a representation suitable for LLVM.
clang is a C, C++, and Objective-C compiler which encompasses preprocessing, parsing, optimization, code generation, assembly, and linking. Depending on which high-level mode setting is passed, Clang will stop before doing a full link.
Clang still uses PassManagerBuilder as of 3.5 (see the PassManagerBuilderWrapper class in BackendUtil.cpp). So I believe extending it with RegisterStandardPasses, as in my blog post, is still the only way to add a pass to Clang's pass manager.
It's frustratingly difficult to find any information about how deprecated the "old" pass manager infrastructure is. But since Clang is still using it, it can't be that deprecated. :)
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