├── .travis.yml
├── Makefile
├── README.md
├── clangtool.cpp
└── test.c


/.travis.yml:
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 1 | language: cpp
 2 | # This is the system compiler, not our LLVM infrastructure
 3 | compiler:
 4 |   - clang
 5 | 
 6 | # Use containers
 7 | sudo: false
 8 | 
 9 | 
10 | addons:
11 |   apt:
12 |     sources:
13 |       - ubuntu-toolchain-r-test
14 |       - llvm-toolchain-precise-3.6
15 |     packages:
16 |       - llvm-3.6-dev
17 |       - llvm-3.6
18 |       - clang-3.6
19 | 
20 | before_script:
21 |   - export CC=clang-3.6
22 |   - export CXX=clang++-3.6
23 |   - export LLVM_CONFIG=llvm-config-3.6
24 | 
25 | # -e == environment vars override makevars
26 | script:
27 |   - make -e test
28 | 
29 | notifications:
30 |   email: false
31 | 


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/Makefile:
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 1 | all: clangtool.so
 2 | 
 3 | CXX=clang++
 4 | CC=clang
 5 | LLVM_CONFIG=llvm-config
 6 | 
 7 | # Flags for building shared libraries.
 8 | SYSTEM=$(shell uname)
 9 | ifeq ($(SYSTEM), Darwin)
10 | 	CXXFLAGS= -fno-common 
11 | 	LDFLAGS= -dynamiclib -Wl,-flat_namespace -Wl,-undefined,suppress 
12 | endif
13 | ifeq ($(SYSTEM), Linux)
14 | 	CXXFLAGS= -fPIC 
15 | 	LDFLAGS= -shared 
16 | endif
17 | 
18 | clangtool.so : %.so: %.cpp
19 | 	$(CXX) $(CXXFLAGS) $< -o $@ `$(LLVM_CONFIG) --cxxflags` $(LDFLAGS)
20 | 
21 | CLANGTOOL_FLAGS=-Xclang -load -Xclang ./clangtool.so
22 | 
23 | .PHONY: test testO0 testO2
24 | test: testO0 testO2
25 | 
26 | testO0: test.c clangtool.so
27 | 	$(CC) $(CLANGTOOL_FLAGS) -O0 -o test test.c
28 | 
29 | testO2: test.c clangtool.so
30 | 	$(CC) $(CLANGTOOL_FLAGS) -O2 -o test test.c
31 | 
32 | clean:
33 | 	rm -f clangtool.so test
34 | 
35 | 


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/README.md:
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 1 | ## Using LLVM plugins with clang
 2 | 
 3 | [![build status](https://travis-ci.org/rdadolf/clangtool.svg?branch=master)](https://travis-ci.org/rdadolf/clangtool)
 4 | 
 5 | The [LLVM docs](http://llvm.org/docs/WritingAnLLVMPass.html) suggest using `opt` to load and run custom passes. This works, but for certain tasks, like building programs with complicated Makefiles or unusual environments, it is less than ideal. Instead, LLVM provides a hook to allow plugin modules to be run automatically when loaded by clang. This lets you add a couple of flags and use clang (and your pass) as a drop-in replacement for your normal C compiler. These files demonstrate how that works.
 6 | 
 7 | ### Using clangtool:
 8 | 
 9 | Two steps:
10 | 
11 | 1. Build your custom LLVM pass the normal way (as a shared library with the appropriate llvm flags).
12 | 
13 | 2. Run `clang` on your input code with the following extra options:
14 | 
15 |         clang -Xclang -load -Xclang <custom-pass>.so ...
16 | 
17 | That's it. Your pass will be run automatically. You can specify these with `CFLAGS` in a Makefile, override `CC` or `CXX`, or write a script to wrap clang and use that.
18 | 
19 | ### How it works:
20 | 
21 | The key is a static class called `RegisterStandardPasses`, which is defined in the `PassManagerBuilder.h` header. The constuctor for this class calls the `addGlobalExtension` function, which in turn adds your custom pass to the list of extensions that are loaded by default.
22 | 


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/clangtool.cpp:
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 1 | #include "llvm/Pass.h"
 2 | #include "llvm/IR/BasicBlock.h"
 3 | #include "llvm/PassRegistry.h"
 4 | #include "llvm/PassManager.h"
 5 | #include "llvm/Transforms/IPO/PassManagerBuilder.h"
 6 | // For output
 7 | #include "llvm/Support/raw_ostream.h"
 8 | 
 9 | using namespace llvm;
10 | 
11 | // Example pass: just dumps the insns for every block.
12 | namespace {
13 |   struct ClangTool : public BasicBlockPass {
14 |     static char ID;
15 |     ClangTool() : BasicBlockPass(ID) {}
16 |     virtual bool runOnBasicBlock(BasicBlock &BB) {
17 |       BasicBlock::iterator i;
18 |       errs() << "Basic Block\n";
19 |       for( i=BB.begin(); i!=BB.end(); i++ ) {
20 |         errs() << "  " << i->getOpcodeName() << "\n";
21 |       }
22 |       return false;
23 |     }
24 |   };
25 | }
26 | 
27 | // Pass info
28 | char ClangTool::ID = 0; // LLVM ignores the actual value
29 | static RegisterPass<ClangTool> X("clangtool", "Example pass", false, false);
30 | 
31 | // Pass loading stuff
32 | // To use, run: clang -Xclang -load -Xclang <your-pass>.so <other-args> ...
33 | 
34 | // This function is of type PassManagerBuilder::ExtensionFn
35 | static void loadPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
36 |   PM.add(new ClangTool());
37 | }
38 | // These constructors add our pass to a list of global extensions.
39 | static RegisterStandardPasses clangtoolLoader_Ox(PassManagerBuilder::EP_OptimizerLast, loadPass);
40 | static RegisterStandardPasses clangtoolLoader_O0(PassManagerBuilder::EP_EnabledOnOptLevel0, loadPass);
41 | 
42 | // Note: The location EP_OptimizerLast places this pass at the end of the list
43 | // of *optimizations*. That means on -O0, it does not get run.
44 | //
45 | // In general, adding your pass twice will cause it to run twice, but in this
46 | // particular case, the two are disjoint (EP_EnabledOnOptLevel0 only runs if
47 | // you're in -O0, and EP_OptimizerLast only runs if you're not). You can check
48 | // include/llvm/Transforms/IPO/PassManagerBuilder.h header and
49 | // lib/Transforms/IPO/PassManagerBuilder.cpp file for the exact behavior.
50 | 


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/test.c:
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 1 | #include <stdio.h>
 2 | 
 3 | int fib(int x) {
 4 |   if(x<2)
 5 |     return 1;
 6 |   else
 7 |     return fib(x-1) + fib(x-2);
 8 | }
 9 | 
10 | int main(int argc, char **argv)
11 | {
12 |   int i;
13 |   printf("fib(5): %d\n", fib(5));
14 |   return 0;
15 | }
16 | 


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