Prerequisites:

1. LLVM_INSTALL set to the llvm-build directory created below
2. LLVM_HOME set to the llvm-src directory created below
3. CHIMES_HOME set to the root directory this repo is cloned to
4. CUDA_HOME set to the root of your CUDA installation
5. LD_LIBRARY_PATH/DYLD_LIBRARY_PATH has ${CHIMES_HOME}/src/libchimes and ${CHIMES_HOME}/src/libchimes/xxhash

The steps to install CHIMES are listed below. There is also an install.sh script provided in the root directory of this project (though it is not guaranteed to work on all systems).

1. Download LLVM 3.5.1 from http://llvm.org/releases/3.5.1/llvm-3.5.1.src.tar.xz and extract to llvm-src
2. Download Clang 3.5.1 from http://llvm.org/releases/3.5.1/cfe-3.5.1.src.tar.xz and extract to llvm-src/tools/clang
3. Download Compiler RT 3.5.1 from http://llvm.org/releases/3.5.1/compiler-rt-3.5.1.src.tar.xz and extract to llvm-src/projects/compiler-rt
4. git clone [email protected]:agrippa/chimes.git
5. cd llvm-src/lib/Transforms && ln -s ${CHIMES_HOME}/src/preprocessing/Play
6. Edit llvm-src/lib/Transforms/Makefile to add the Play/ directory to the PARALLEL_DIRS list
7. Edit llvm-src/lib/Transforms/CMakeLists.txt, appending the line add_subdirectory(Play)
8. mkdir llvm-build
9. cd llvm-build && ../llvm-src/configure --enable-optimized=no --enable-profiling=yes && make

When building, you must build LLVM with the GNU compilers to enable profiling. If your machine defaults to something else (e.g. clang on MacOS) then you can explicitly force LLVM to be built with GNU by setting the CC, CXX, and CPP environment variables. For example, on my Mac:

    CC=/usr/local/bin/gcc CXX=/usr/local/bin/g++ CPP=/usr/local/bin/cpp \
        ../llvm-src/configure --enable-optimized=no --enable-profiling=yes

You will also need to create a file at chimes/src/common.conf that contains a pointer to the desired C/C++ compiler for your system. For example, mine contains:

    GXX=/usr/local/bin/g++

There have been several times I've wanted to add a new attribute to clang. The process is straightforward, but unfortunately requires a modification to a codebase that is not versioned with the rest of the CHIMES code (the clang repo). Therefore, I include a step-by-step guide to reproduce my changes in your own clang installation. This information is based on:

http://clang.llvm.org/docs/InternalsManual.html#include-clang-basic-attr-td

1. Add a definition of the attribute in clang/include/clang/Basic/Attr.td. I've added the following attributes:

    def NoCheckpoint : InheritableAttr {
      let Spellings = [GCC<"nocheckpoint">, Declspec<"nocheckpoint">];
      let Documentation = [Undocumented];
    }
    
    def Allocator : InheritableAttr {
      let Spellings = [GCC<"allocator">, Declspec<"allocator">];
      let Documentation = [Undocumented];
    }
   

2. Add boiler plate to clang/lib/Sema/SemaDeclAttr.cpp for actually handling that attribute. The attributes I've added generally just serve as markers for me to fetch in my own clang plugins so I don't want to modify the behavior of clang. I just use handleSimpleAttribute in the massive attribute switch statement in ProcessDeclAttribute:

    case AttributeList::AT_NoCheckpoint:
      handleSimpleAttribute<NoCheckpointAttr>(S, D, Attr);
      break;
    case AttributeList::AT_Allocator:
      handleSimpleAttribute<AllocatorAttr>(S, D, Attr);
      break;
   

3. That's all of the changes to the core of clang, but I generally also need to check if these attributes are applied to an element from a clang tool. As far as I can tell, getting attribute information is not possible from LLVM. From a clang tool, you can do something like the following:

    clang::CallExpr *call = ...;
    const clang::FunctionDecl *callee = call->getDirectCallee();
    if (callee && callee->hasAttrs()) {
        for (clang::AttrVec::const_iterator i = callee->getAttrs().begin(),
                e = callee->getAttrs().end(); i != e; i++) {
            clang::NoCheckpointAttr *a = clang::dyn_cast<clang::NoCheckpointAttr>(*i);
            if (a) {
                // This function declaration has the nocheckpoint attribute
                ...
            }
        }
    }