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Shawn Kim

2011-Sep-16 18:25 UTC

[LLVMdev] How to duplicate a function?

Hi all,

Sorry for the inconvenient about the previous post. The files were not
attached. So I put them here again.

I am a newbie in LLVM and I am trying to replace the function like:

old function               ||            new function
=====================================int haha(int a) {                       
int haha(int a, char* ID) {

                            ===>


}                                            }

Of course in the newly replaced function "int haha(int, char*ID)", I
want to
insert some instrumentation code.

Here is my code that I am working on till now and it generates segmentation
fault in the place I comment with "//////////////////////"
Can you help me? Any advice will be helpful because I am a beginner in llvm.


Thank you in advance.
Shawn.


duplicateFunction.cpp
============================================================================
//===- duplicateFunction.cpp - Writing an LLVM Pass
-----------------------===//
//
//                     The LLVM Compiler Infrastructure
//
//===----------------------------------------------------------------------===//
//
// This file implements the LLVM duplicating function pass.
// It starts by computing a new prototype for the function,
// which is the same as the old function, but has an extra argument.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Pass.h"
#include "llvm/Function.h"
#include "llvm/Module.h"
#include "llvm/CallingConv.h"
#include "llvm/DerivedTypes.h"
#include "llvm/InstrTypes.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/BasicBlock.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/CallSite.h"
using namespace llvm;

namespace {
    Constant *f;
    Function *Fn;
    FunctionType *FTy;
    Type *RetTy;
    std::vector<Type*> Params;
    class DP : public FunctionPass {

      public:
        static char ID;

        DP() : FunctionPass(ID) {}

        virtual bool doInitialization(Module &M);
        virtual bool runOnFunction(Function &F);
        virtual bool doFinalization(Module &mdl) {
            mdl.dump();
            return true;
        }
    }; /* class */
}

char DP::ID = 0;
static RegisterPass<DP> IC("duplicateFunction", "Duplicate
Function Pass");


bool DP::doInitialization(Module &M) {

    // find the function that we want to change.
    Fn = M.getFunction("haha");

    // Start by computing a new prototype for the function, which is the
same as
    // the old function, but has an extra argument.
    FTy = Fn->getFunctionType();

    // Find out the return value.
    RetTy = FTy->getReturnType();

    // set the calling convention to C.
    // so, we interoperate with C Code properly.
    Function *tmp = cast<Function>(Fn);
    tmp->setCallingConv(CallingConv::C);

    return true;
}

bool DP::runOnFunction(Function &F) {
#if 0
    Value *param;

    // Find the instruction before which you want to insert the function
call
    Instruction *nextInstr = F.back().getTerminator();

    // Create the actual parameter for the function call
    param = ConstantInt::get(Type::getInt32Ty(F.getContext()), 333);

    // create and insert the function call
    //CallInst::Create(f, param, "", nextInstr);
    CallInst::Create(Fn, param, "", nextInstr);

    // indicates that we changed the code
    //return true;
#endif
    Type *NRetTy;

    std::vector<Type*> Params(FTy->param_begin(), FTy->param_end());
    FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params,
false);

    // Create the new function body and insert it into the module...
    Function *NF = Function::Create(NFTy, Fn->getLinkage());
    NF->copyAttributesFrom(Fn);
    Fn->getParent()->getFunctionList().insert(Fn, NF);
    NF->takeName(Fn);

    for (Function::arg_iterator AI=F.arg_begin(), AE=F.arg_end(),
NAI=NF->arg_begin();
         AI != AE; ++AI, ++NAI) {
        NAI->takeName(AI);
    }

    // Since we have now create the new function, splice the body of the old
    // function right into the new function, leaving the old rotting hulk of
the
    // function empty.
    NF->getBasicBlockList().splice(NF->begin(), F.getBasicBlockList());

    llvm::Value *Globals = --NF->arg_end();
    Globals->setName("IOCallIDs");

    // Now, exploit all return instructions.
    for (Function::iterator BI = NF->begin(), BE = NF->end(); BI != BE;
++BI) {
        if (ReturnInst *RI
llvm::dyn_cast<llvm::ReturnInst>(BI->getTerminator())) {
            // Don't support functions that have multiple return values.
            assert(RI->getNumOperands() < 2);

            // Insert a new load instruction to return.

/////////////////////////////////////////////////////////////////////////////////////
HERE, GENERATE ERROR

/////////////////////////////////////////////////////////////////////////////////////
            Value *Load = new llvm::LoadInst(Globals, "globalsret",
RI);

/////////////////////////////////////////////////////////////////////////////////////

            // Return type is void
            if ( RetTy->isVoidTy() ) {
//                ReturnInst::Create(Load, 0, RI); // Return void
                ReturnInst::Create(F.getContext(), 0, RI); // Return void
                RI->getParent()->getInstList().erase(RI);
            } else {
                // Start with an empty struct.
                Value *Return = ConstantAggregateZero::get(NRetTy);
                DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');

                // Insert the original return value in field 0
                Return = InsertValueInst::Create(Return, RI->getOperand(0),
0, "ret", RI);
                DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');

                // Insert the globals return value in field 1
                Return = InsertValueInst::Create(Return, Load, 1,
"ret",
RI); // <- maybe useless
                DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');

                // Update the return instruction
                RI->setOperand(0, Return);
            }
        } // if
    } // for

    // Replace all uses of the old arguments with the new arguments.
    for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(), NI
NF->arg_begin();
         I != E; ++I, ++NI) {
        I->replaceAllUsesWith(NI);
    }

#if 1
    // Replace all callers
    while ( !F.use_empty() ) {
        CallSite CS(F.use_back());
        Instruction *Call = CS.getInstruction();
//        Function *CallingF = Call->getParent()->getParent();

        // Get the global struct in our caller.
        //Value* CallerGlobals = ModifyFunctionRecursive(CallingF).first;
        Value* CallerGlobals = NULL; // <- This should be modified later.

        // Copy the existing arguments
        std::vector<Value*> Args;
        Args.reserve(CS.arg_size());
        CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();

        // First, copy regular arguments
        for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i, ++AI) {
            Args.push_back(*AI);
        }
        // Then, insert the new argument
        Args.push_back(CallerGlobals);
        // Lastly, copy any remaining varargs
        for (; AI != AE; ++AI) {
            Args.push_back(*AI);
        }

        Instruction *New;
        Instruction *Before = Call;
        if ( InvokeInst *II = dyn_cast<InvokeInst>(Call) ) {
            New = InvokeInst::Create(NF, II->getNormalDest(),
II->getUnwindDest(), Args, "", Before);
            cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
//          cast<InvokeInst>(New)->setParamAttrs(CS.getParamAttrs());
            cast<InvokeInst>(New)->setAttributes(CS.getAttributes());
        } else {
            New = CallInst::Create(NF, Args, "", Before);
            cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
//          cast<CallInst>(New)->setParamAttrs(CS.getParamAttrs());
            cast<CallInst>(New)->setAttributes(CS.getAttributes());
            if ( cast<CallInst>(Call)->isTailCall() ) {
                cast<CallInst>(New)->setTailCall();
            }
        }

        if (Call->hasName()) {
            New->takeName(Call);
        } else {
            New->setName(NF->getName() + ".ret");
        }

        Value *GlobalsRet;
        if ( Call->getType()->isVoidTy() ) {
            // The original function returned nothing, so the new function
returns
            // only the globals
            GlobalsRet = New;
        } else {
            // Split the values
            Value *OrigRet = ExtractValueInst::Create(New, 0,
"origret",
Before);
            GlobalsRet     = ExtractValueInst::Create(New, 1,
"globalsret",
Before);
            // Replace all the uses of the original result
            Call->replaceAllUsesWith(OrigRet);
        }

        // Now, store the globals back
        new StoreInst(GlobalsRet, CallerGlobals, Before);

        DEBUG(errs() << "Call " << *Call << "
replaced, function is now " <<
*Call->getParent()->getParent() << "\n");

        // Finally, remove the old call from the program, reducing the
use-count of F.
        Call->eraseFromParent();

    } // while
#endif
    return true;
}


test.c
===================================================================================#include
<stdio.h>
#include <stdlib.h>

int v[200];
int haha(int);

int main()
{
    int i;
    int n=100;

    if ( !haha(n) )
        exit(-1);

    return 1;
}

int haha(int n)
//int haha(int n, char* IOCallIDs)
{
    int i;
    for (i=1; i<n; i++)
        v[i] = v[i-1] + v[i];

    printf ("hahaha\n");
    return 1;
}

Makefile
===================================================================================LLVM_CONFIG?=llvm-config

# location of the source
# useful if you want separate source and object directories.
SRC_DIR?=$(PWD)

#ifndef VERBOSE
#    QUIET:=@
#endif

COMMON_FLAGS=-Wall -Wextra #-fvisibility=hidden
CFLAGS+=$(COMMON_FLAGS) $(shell $(LLVM_CONFIG) --cflags)
CXXFLAGS+=$(COMMON_FLAGS) $(shell $(LLVM_CONFIG) --cxxflags)

#ifeq ($(shell uname),Darwin)
#LOADABLE_MODULE_OPTIONS=-bundle -undefined dynamic_lookup
#else
LOADABLE_MODULE_OPTIONS=-shared -Wl,-O1
#endif

TEST_C=test.c
TEST_FILE=$(subst .c,.s, $(TEST_C))
PLUGIN=duplicateFunction.so
PLUGIN_OBJECTS=duplicateFunction.o

ALL_OBJECTS=$(PLUGIN_OBJECTS)
ALL_TARGETS=$(PLUGIN) $(TEST_FILE)

CPP_OPTIONS+=$(CPPFLAGS) $(shell $(LLVM_CONFIG) --cppflags) -MD -MP
-I$(SRC_DIR)

LD_OPTIONS+=$(LDFLAGS) $(shell $(LLVM_CONFIG) --ldflags)

all: $(ALL_TARGETS)

%.o : $(SRC_DIR)/%.cpp
    @echo Compiling $*.cpp
    $(QUIET)$(CXX) -c $(CPP_OPTIONS) $(CXXFLAGS) $<

$(PLUGIN): $(PLUGIN_OBJECTS)
    @echo Linking $@
    $(QUIET)$(CXX) -o $@ $(LOADABLE_MODULE_OPTIONS) $(CXXFLAGS)
$(LD_OPTIONS) $(PLUGIN_OBJECTS)

RUN_FLAGS=-duplicateFunction

$(TEST_FILE): $(TEST_C)
    clang -g -O3 -S -emit-llvm $^
#    clang -g -O0 -S -emit-llvm $^
#     clang -O0 -S -emit-llvm $^
run:
    opt -load ./$(PLUGIN) $(RUN_FLAGS) < $(TEST_FILE) > /dev/null 2>
after.s
#    opt -load ./$(PLUGIN) $(RUN_FLAGS) < $(TEST_FILE) > /dev/null

clean:
    $(QUIET)rm -f $(ALL_OBJECTS) *.d $(PLUGIN) $(TEST_FILE)


-include $(ALL_OBJECTS:.o=.d)
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Dmitry N. Mikushin

2011-Sep-26 22:04 UTC

head link

[LLVMdev] How to duplicate a function?

Hi Shawn,

Probably I can answer specifically the question "how to replace old
function call with new one, adding extra char* argument".

Method for gathering information: grep with context for one keyword in
LLVM source and then look for another in results:

find . -name *.cpp -exec grep "CallInst" {} -C 100 \; | less

Results:

1) tools/bugpoint/Miscompilation.cpp gives an example of creating
string array and adding it into call args list starting at line 826:

        Constant *InitArray = ConstantArray::get(F->getContext(),
F->getName());
        GlobalVariable *funcName 
2) Using (1) I implemented my own version here, with more comments:

https://hpcforge.org/scm/viewvc.php/branches/accurate/src/frontend/compile.cpp?revision=476&root=kernelgen&view=markup

I hope it's helpful,
- D.

2011/9/16 Shawn Kim <shawn.subscribe at
gmail.com>:> Hi all,
>
> Sorry for the inconvenient about the previous post. The files were not
> attached. So I put them here again.
>
> I am a newbie in LLVM and I am trying to replace the function like:
>
> old function               ||            new function
> =============================> ========> int haha(int a)
{                        int haha(int a, char* ID) {
>
>                             ===>
>
>
> }                                            }
>
> Of course in the newly replaced function "int haha(int,
char*ID)", I want to
> insert some instrumentation code.
>
> Here is my code that I am working on till now and it generates segmentation
> fault in the place I comment with "//////////////////////"
> Can you help me? Any advice will be helpful because I am a beginner in
llvm.
>
>
> Thank you in advance.
> Shawn.
>
>
> duplicateFunction.cpp
>
============================================================================>
> //===- duplicateFunction.cpp - Writing an LLVM Pass
> -----------------------===//
> //
> //                     The LLVM Compiler Infrastructure
> //
>
//===----------------------------------------------------------------------===//
> //
> // This file implements the LLVM duplicating function pass.
> // It starts by computing a new prototype for the function,
> // which is the same as the old function, but has an extra argument.
> //
>
//===----------------------------------------------------------------------===//
> #include "llvm/Transforms/Utils/Cloning.h"
> #include "llvm/Pass.h"
> #include "llvm/Function.h"
> #include "llvm/Module.h"
> #include "llvm/CallingConv.h"
> #include "llvm/DerivedTypes.h"
> #include "llvm/InstrTypes.h"
> #include "llvm/Constants.h"
> #include "llvm/Instructions.h"
> #include "llvm/Support/raw_ostream.h"
> #include "llvm/Transforms/Utils/BasicBlockUtils.h"
> #include "llvm/BasicBlock.h"
> #include "llvm/Support/Debug.h"
> #include "llvm/Support/CallSite.h"
> using namespace llvm;
>
> namespace {
>     Constant *f;
>     Function *Fn;
>     FunctionType *FTy;
>     Type *RetTy;
>     std::vector<Type*> Params;
>     class DP : public FunctionPass {
>
>       public:
>         static char ID;
>
>         DP() : FunctionPass(ID) {}
>
>         virtual bool doInitialization(Module &M);
>         virtual bool runOnFunction(Function &F);
>         virtual bool doFinalization(Module &mdl) {
>             mdl.dump();
>             return true;
>         }
>     }; /* class */
> }
>
> char DP::ID = 0;
> static RegisterPass<DP> IC("duplicateFunction",
"Duplicate Function Pass");
>
>
> bool DP::doInitialization(Module &M) {
>
>     // find the function that we want to change.
>     Fn = M.getFunction("haha");
>
>     // Start by computing a new prototype for the function, which is the
> same as
>     // the old function, but has an extra argument.
>     FTy = Fn->getFunctionType();
>
>     // Find out the return value.
>     RetTy = FTy->getReturnType();
>
>     // set the calling convention to C.
>     // so, we interoperate with C Code properly.
>     Function *tmp = cast<Function>(Fn);
>     tmp->setCallingConv(CallingConv::C);
>
>     return true;
> }
>
> bool DP::runOnFunction(Function &F) {
> #if 0
>     Value *param;
>
>     // Find the instruction before which you want to insert the function
> call
>     Instruction *nextInstr = F.back().getTerminator();
>
>     // Create the actual parameter for the function call
>     param = ConstantInt::get(Type::getInt32Ty(F.getContext()), 333);
>
>     // create and insert the function call
>     //CallInst::Create(f, param, "", nextInstr);
>     CallInst::Create(Fn, param, "", nextInstr);
>
>     // indicates that we changed the code
>     //return true;
> #endif
>     Type *NRetTy;
>
>     std::vector<Type*> Params(FTy->param_begin(),
FTy->param_end());
>     FunctionType *NFTy = FunctionType::get(FTy->getReturnType(), Params,
> false);
>
>     // Create the new function body and insert it into the module...
>     Function *NF = Function::Create(NFTy, Fn->getLinkage());
>     NF->copyAttributesFrom(Fn);
>     Fn->getParent()->getFunctionList().insert(Fn, NF);
>     NF->takeName(Fn);
>
>     for (Function::arg_iterator AI=F.arg_begin(), AE=F.arg_end(),
> NAI=NF->arg_begin();
>          AI != AE; ++AI, ++NAI) {
>         NAI->takeName(AI);
>     }
>
>     // Since we have now create the new function, splice the body of the
old
>     // function right into the new function, leaving the old rotting hulk
of
> the
>     // function empty.
>     NF->getBasicBlockList().splice(NF->begin(),
F.getBasicBlockList());
>
>     llvm::Value *Globals = --NF->arg_end();
>     Globals->setName("IOCallIDs");
>
>     // Now, exploit all return instructions.
>     for (Function::iterator BI = NF->begin(), BE = NF->end(); BI !=
BE;
> ++BI) {
>         if (ReturnInst *RI >
llvm::dyn_cast<llvm::ReturnInst>(BI->getTerminator())) {
>             // Don't support functions that have multiple return
values.
>             assert(RI->getNumOperands() < 2);
>
>             // Insert a new load instruction to return.
>
>
/////////////////////////////////////////////////////////////////////////////////////
> HERE, GENERATE ERROR
>
>
/////////////////////////////////////////////////////////////////////////////////////
>             Value *Load = new llvm::LoadInst(Globals,
"globalsret", RI);
>
>
/////////////////////////////////////////////////////////////////////////////////////
>
>             // Return type is void
>             if ( RetTy->isVoidTy() ) {
> //                ReturnInst::Create(Load, 0, RI); // Return void
>                 ReturnInst::Create(F.getContext(), 0, RI); // Return void
>                 RI->getParent()->getInstList().erase(RI);
>             } else {
>                 // Start with an empty struct.
>                 Value *Return = ConstantAggregateZero::get(NRetTy);
>                 DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');
>
>                 // Insert the original return value in field 0
>                 Return = InsertValueInst::Create(Return,
RI->getOperand(0),
> 0, "ret", RI);
>                 DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');
>
>                 // Insert the globals return value in field 1
>                 Return = InsertValueInst::Create(Return, Load, 1,
"ret",
> RI); // <- maybe useless
>                 DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');
>
>                 // Update the return instruction
>                 RI->setOperand(0, Return);
>             }
>         } // if
>     } // for
>
>     // Replace all uses of the old arguments with the new arguments.
>     for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(), NI >
NF->arg_begin();
>          I != E; ++I, ++NI) {
>         I->replaceAllUsesWith(NI);
>     }
>
> #if 1
>     // Replace all callers
>     while ( !F.use_empty() ) {
>         CallSite CS(F.use_back());
>         Instruction *Call = CS.getInstruction();
> //        Function *CallingF = Call->getParent()->getParent();
>
>         // Get the global struct in our caller.
>         //Value* CallerGlobals = ModifyFunctionRecursive(CallingF).first;
>         Value* CallerGlobals = NULL; // <- This should be modified
later.
>
>         // Copy the existing arguments
>         std::vector<Value*> Args;
>         Args.reserve(CS.arg_size());
>         CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
>
>         // First, copy regular arguments
>         for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i, ++AI)
{
>             Args.push_back(*AI);
>         }
>         // Then, insert the new argument
>         Args.push_back(CallerGlobals);
>         // Lastly, copy any remaining varargs
>         for (; AI != AE; ++AI) {
>             Args.push_back(*AI);
>         }
>
>         Instruction *New;
>         Instruction *Before = Call;
>         if ( InvokeInst *II = dyn_cast<InvokeInst>(Call) ) {
>             New = InvokeInst::Create(NF, II->getNormalDest(),
> II->getUnwindDest(), Args, "", Before);
>            
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
> //         
cast<InvokeInst>(New)->setParamAttrs(CS.getParamAttrs());
>            
cast<InvokeInst>(New)->setAttributes(CS.getAttributes());
>         } else {
>             New = CallInst::Create(NF, Args, "", Before);
>            
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
> //         
cast<CallInst>(New)->setParamAttrs(CS.getParamAttrs());
>            
cast<CallInst>(New)->setAttributes(CS.getAttributes());
>             if ( cast<CallInst>(Call)->isTailCall() ) {
>                 cast<CallInst>(New)->setTailCall();
>             }
>         }
>
>         if (Call->hasName()) {
>             New->takeName(Call);
>         } else {
>             New->setName(NF->getName() + ".ret");
>         }
>
>         Value *GlobalsRet;
>         if ( Call->getType()->isVoidTy() ) {
>             // The original function returned nothing, so the new function
> returns
>             // only the globals
>             GlobalsRet = New;
>         } else {
>             // Split the values
>             Value *OrigRet = ExtractValueInst::Create(New, 0,
"origret",
> Before);
>             GlobalsRet     = ExtractValueInst::Create(New, 1,
"globalsret",
> Before);
>             // Replace all the uses of the original result
>             Call->replaceAllUsesWith(OrigRet);
>         }
>
>         // Now, store the globals back
>         new StoreInst(GlobalsRet, CallerGlobals, Before);
>
>         DEBUG(errs() << "Call " << *Call <<
" replaced, function is now " <<
> *Call->getParent()->getParent() << "\n");
>
>         // Finally, remove the old call from the program, reducing the
> use-count of F.
>         Call->eraseFromParent();
>
>     } // while
> #endif
>     return true;
> }
>
>
> test.c
>
===================================================================================>
#include <stdio.h>
> #include <stdlib.h>
>
> int v[200];
> int haha(int);
>
> int main()
> {
>     int i;
>     int n=100;
>
>     if ( !haha(n) )
>         exit(-1);
>
>     return 1;
> }
>
> int haha(int n)
> //int haha(int n, char* IOCallIDs)
> {
>     int i;
>     for (i=1; i<n; i++)
>         v[i] = v[i-1] + v[i];
>
>     printf ("hahaha\n");
>     return 1;
> }
>
> Makefile
>
===================================================================================>
LLVM_CONFIG?=llvm-config
>
> # location of the source
> # useful if you want separate source and object directories.
> SRC_DIR?=$(PWD)
>
> #ifndef VERBOSE
> #    QUIET:=@
> #endif
>
> COMMON_FLAGS=-Wall -Wextra #-fvisibility=hidden
> CFLAGS+=$(COMMON_FLAGS) $(shell $(LLVM_CONFIG) --cflags)
> CXXFLAGS+=$(COMMON_FLAGS) $(shell $(LLVM_CONFIG) --cxxflags)
>
> #ifeq ($(shell uname),Darwin)
> #LOADABLE_MODULE_OPTIONS=-bundle -undefined dynamic_lookup
> #else
> LOADABLE_MODULE_OPTIONS=-shared -Wl,-O1
> #endif
>
> TEST_C=test.c
> TEST_FILE=$(subst .c,.s, $(TEST_C))
> PLUGIN=duplicateFunction.so
> PLUGIN_OBJECTS=duplicateFunction.o
>
> ALL_OBJECTS=$(PLUGIN_OBJECTS)
> ALL_TARGETS=$(PLUGIN) $(TEST_FILE)
>
> CPP_OPTIONS+=$(CPPFLAGS) $(shell $(LLVM_CONFIG) --cppflags) -MD -MP
> -I$(SRC_DIR)
>
> LD_OPTIONS+=$(LDFLAGS) $(shell $(LLVM_CONFIG) --ldflags)
>
> all: $(ALL_TARGETS)
>
> %.o : $(SRC_DIR)/%.cpp
>     @echo Compiling $*.cpp
>     $(QUIET)$(CXX) -c $(CPP_OPTIONS) $(CXXFLAGS) $<
>
> $(PLUGIN): $(PLUGIN_OBJECTS)
>     @echo Linking $@
>     $(QUIET)$(CXX) -o $@ $(LOADABLE_MODULE_OPTIONS) $(CXXFLAGS)
> $(LD_OPTIONS) $(PLUGIN_OBJECTS)
>
> RUN_FLAGS=-duplicateFunction
>
> $(TEST_FILE): $(TEST_C)
>     clang -g -O3 -S -emit-llvm $^
> #    clang -g -O0 -S -emit-llvm $^
> #     clang -O0 -S -emit-llvm $^
> run:
>     opt -load ./$(PLUGIN) $(RUN_FLAGS) < $(TEST_FILE) > /dev/null
2> after.s
> #    opt -load ./$(PLUGIN) $(RUN_FLAGS) < $(TEST_FILE) > /dev/null
>
> clean:
>     $(QUIET)rm -f $(ALL_OBJECTS) *.d $(PLUGIN) $(TEST_FILE)
>
>
> -include $(ALL_OBJECTS:.o=.d)
>
>
>
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>

Duncan Sands

2011-Sep-27 07:47 UTC

head link

[LLVMdev] How to duplicate a function?

Hi Shawn, did you build LLVM with assertions enabled?  You should, since you
then get helpful error messages rather than obscure crashes.  Also, take a look
at ArgumentPromotion.cpp as an example of the kind of thing you are trying to
do.

Ciao, Duncan.
> Sorry for the inconvenient about the previous post. The files were not
attached.
> So I put them here again.
>
> I am a newbie in LLVM and I am trying to replace the function like:
>
> old function               ||            new function
> =============================> ========> int haha(int a) {           
int haha(int a, char* ID) {
>
>                              ===>
>
>
> }                                            }
>
> Of course in the newly replaced function "int haha(int,
char*ID)", I want to
> insert some instrumentation code.
>
> Here is my code that I am working on till now and it generates segmentation
> fault in the place I comment with "//////////////////////"
> Can you help me? Any advice will be helpful because I am a beginner in
llvm.
>
>
> Thank you in advance.
> Shawn.
>
>
> duplicateFunction.cpp
>
============================================================================>
> //===- duplicateFunction.cpp - Writing an LLVM Pass
-----------------------===//
> //
> //                     The LLVM Compiler Infrastructure
> //
>
//===----------------------------------------------------------------------===//
> //
> // This file implements the LLVM duplicating function pass.
> // It starts by computing a new prototype for the function,
> // which is the same as the old function, but has an extra argument.
> //
>
//===----------------------------------------------------------------------===//
> #include "llvm/Transforms/Utils/Cloning.h"
> #include "llvm/Pass.h"
> #include "llvm/Function.h"
> #include "llvm/Module.h"
> #include "llvm/CallingConv.h"
> #include "llvm/DerivedTypes.h"
> #include "llvm/InstrTypes.h"
> #include "llvm/Constants.h"
> #include "llvm/Instructions.h"
> #include "llvm/Support/raw_ostream.h"
> #include "llvm/Transforms/Utils/BasicBlockUtils.h"
> #include "llvm/BasicBlock.h"
> #include "llvm/Support/Debug.h"
> #include "llvm/Support/CallSite.h"
> using namespace llvm;
>
> namespace {
>      Constant *f;
>      Function *Fn;
>      FunctionType *FTy;
>      Type *RetTy;
>      std::vector<Type*> Params;
>      class DP : public FunctionPass {
>
>        public:
>          static char ID;
>
>          DP() : FunctionPass(ID) {}
>
>          virtual bool doInitialization(Module &M);
>          virtual bool runOnFunction(Function &F);
>          virtual bool doFinalization(Module &mdl) {
>              mdl.dump();
>              return true;
>          }
>      }; /* class */
> }
>
> char DP::ID = 0;
> static RegisterPass<DP> IC("duplicateFunction",
"Duplicate Function Pass");
>
>
> bool DP::doInitialization(Module &M) {
>
>      // find the function that we want to change.
>      Fn = M.getFunction("haha");
>
>      // Start by computing a new prototype for the function, which is the
same as
>      // the old function, but has an extra argument.
>      FTy = Fn->getFunctionType();
>
>      // Find out the return value.
>      RetTy = FTy->getReturnType();
>
>      // set the calling convention to C.
>      // so, we interoperate with C Code properly.
>      Function *tmp = cast<Function>(Fn);
>      tmp->setCallingConv(CallingConv::C);
>
>      return true;
> }
>
> bool DP::runOnFunction(Function &F) {
> #if 0
>      Value *param;
>
>      // Find the instruction before which you want to insert the function
call
>      Instruction *nextInstr = F.back().getTerminator();
>
>      // Create the actual parameter for the function call
>      param = ConstantInt::get(Type::getInt32Ty(F.getContext()), 333);
>
>      // create and insert the function call
>      //CallInst::Create(f, param, "", nextInstr);
>      CallInst::Create(Fn, param, "", nextInstr);
>
>      // indicates that we changed the code
>      //return true;
> #endif
>      Type *NRetTy;
>
>      std::vector<Type*> Params(FTy->param_begin(),
FTy->param_end());
>      FunctionType *NFTy = FunctionType::get(FTy->getReturnType(),
Params, false);
>
>      // Create the new function body and insert it into the module...
>      Function *NF = Function::Create(NFTy, Fn->getLinkage());
>      NF->copyAttributesFrom(Fn);
>      Fn->getParent()->getFunctionList().insert(Fn, NF);
>      NF->takeName(Fn);
>
>      for (Function::arg_iterator AI=F.arg_begin(), AE=F.arg_end(),
> NAI=NF->arg_begin();
>           AI != AE; ++AI, ++NAI) {
>          NAI->takeName(AI);
>      }
>
>      // Since we have now create the new function, splice the body of the
old
>      // function right into the new function, leaving the old rotting hulk
of the
>      // function empty.
>      NF->getBasicBlockList().splice(NF->begin(),
F.getBasicBlockList());
>
>      llvm::Value *Globals = --NF->arg_end();
>      Globals->setName("IOCallIDs");
>
>      // Now, exploit all return instructions.
>      for (Function::iterator BI = NF->begin(), BE = NF->end(); BI !=
BE; ++BI) {
>          if (ReturnInst *RI >
llvm::dyn_cast<llvm::ReturnInst>(BI->getTerminator())) {
>              // Don't support functions that have multiple return
values.
>              assert(RI->getNumOperands() < 2);
>
>              // Insert a new load instruction to return.
>
>
/////////////////////////////////////////////////////////////////////////////////////
> HERE, GENERATE ERROR
>
>
/////////////////////////////////////////////////////////////////////////////////////
>              Value *Load = new llvm::LoadInst(Globals,
"globalsret", RI);
>
>
/////////////////////////////////////////////////////////////////////////////////////
>              // Return type is void
>              if ( RetTy->isVoidTy() ) {
> //                ReturnInst::Create(Load, 0, RI); // Return void
>                  ReturnInst::Create(F.getContext(), 0, RI); // Return void
>                  RI->getParent()->getInstList().erase(RI);
>              } else {
>                  // Start with an empty struct.
>                  Value *Return = ConstantAggregateZero::get(NRetTy);
>                  DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');
>
>                  // Insert the original return value in field 0
>                  Return = InsertValueInst::Create(Return,
RI->getOperand(0), 0,
> "ret", RI);
>                  DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');
>
>                  // Insert the globals return value in field 1
>                  Return = InsertValueInst::Create(Return, Load, 1,
"ret", RI);
> // <- maybe useless
>                  DEBUG(errs() << "Return: " <<
*Return->getType() << '\n');
>
>                  // Update the return instruction
>                  RI->setOperand(0, Return);
>              }
>          } // if
>      } // for
>
>      // Replace all uses of the old arguments with the new arguments.
>      for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(), NI
> NF->arg_begin();
>           I != E; ++I, ++NI) {
>          I->replaceAllUsesWith(NI);
>      }
>
> #if 1
>      // Replace all callers
>      while ( !F.use_empty() ) {
>          CallSite CS(F.use_back());
>          Instruction *Call = CS.getInstruction();
> //        Function *CallingF = Call->getParent()->getParent();
>
>          // Get the global struct in our caller.
>          //Value* CallerGlobals = ModifyFunctionRecursive(CallingF).first;
>          Value* CallerGlobals = NULL; // <- This should be modified
later.
>
>          // Copy the existing arguments
>          std::vector<Value*> Args;
>          Args.reserve(CS.arg_size());
>          CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
>
>          // First, copy regular arguments
>          for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i,
++AI) {
>              Args.push_back(*AI);
>          }
>          // Then, insert the new argument
>          Args.push_back(CallerGlobals);
>          // Lastly, copy any remaining varargs
>          for (; AI != AE; ++AI) {
>              Args.push_back(*AI);
>          }
>
>          Instruction *New;
>          Instruction *Before = Call;
>          if ( InvokeInst *II = dyn_cast<InvokeInst>(Call) ) {
>              New = InvokeInst::Create(NF, II->getNormalDest(),
> II->getUnwindDest(), Args, "", Before);
>             
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
> //         
cast<InvokeInst>(New)->setParamAttrs(CS.getParamAttrs());
>             
cast<InvokeInst>(New)->setAttributes(CS.getAttributes());
>          } else {
>              New = CallInst::Create(NF, Args, "", Before);
>             
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
> //         
cast<CallInst>(New)->setParamAttrs(CS.getParamAttrs());
>             
cast<CallInst>(New)->setAttributes(CS.getAttributes());
>              if ( cast<CallInst>(Call)->isTailCall() ) {
>                  cast<CallInst>(New)->setTailCall();
>              }
>          }
>
>          if (Call->hasName()) {
>              New->takeName(Call);
>          } else {
>              New->setName(NF->getName() + ".ret");
>          }
>
>          Value *GlobalsRet;
>          if ( Call->getType()->isVoidTy() ) {
>              // The original function returned nothing, so the new function
returns
>              // only the globals
>              GlobalsRet = New;
>          } else {
>              // Split the values
>              Value *OrigRet = ExtractValueInst::Create(New, 0,
"origret", Before);
>              GlobalsRet     = ExtractValueInst::Create(New, 1,
"globalsret",
> Before);
>              // Replace all the uses of the original result
>              Call->replaceAllUsesWith(OrigRet);
>          }
>
>          // Now, store the globals back
>          new StoreInst(GlobalsRet, CallerGlobals, Before);
>
>          DEBUG(errs() << "Call " << *Call <<
" replaced, function is now " <<
> *Call->getParent()->getParent() << "\n");
>
>          // Finally, remove the old call from the program, reducing the
> use-count of F.
>          Call->eraseFromParent();
>
>      } // while
> #endif
>      return true;
> }
>
>
> test.c
>
===================================================================================>
#include <stdio.h>
> #include <stdlib.h>
>
> int v[200];
> int haha(int);
>
> int main()
> {
>      int i;
>      int n=100;
>
>      if ( !haha(n) )
>          exit(-1);
>
>      return 1;
> }
>
> int haha(int n)
> //int haha(int n, char* IOCallIDs)
> {
>      int i;
>      for (i=1; i<n; i++)
>          v[i] = v[i-1] + v[i];
>
>      printf ("hahaha\n");
>      return 1;
> }
>
> Makefile
>
===================================================================================>
LLVM_CONFIG?=llvm-config
>
> # location of the source
> # useful if you want separate source and object directories.
> SRC_DIR?=$(PWD)
>
> #ifndef VERBOSE
> #    QUIET:=@
> #endif
>
> COMMON_FLAGS=-Wall -Wextra #-fvisibility=hidden
> CFLAGS+=$(COMMON_FLAGS) $(shell $(LLVM_CONFIG) --cflags)
> CXXFLAGS+=$(COMMON_FLAGS) $(shell $(LLVM_CONFIG) --cxxflags)
>
> #ifeq ($(shell uname),Darwin)
> #LOADABLE_MODULE_OPTIONS=-bundle -undefined dynamic_lookup
> #else
> LOADABLE_MODULE_OPTIONS=-shared -Wl,-O1
> #endif
>
> TEST_C=test.c
> TEST_FILE=$(subst .c,.s, $(TEST_C))
> PLUGIN=duplicateFunction.so
> PLUGIN_OBJECTS=duplicateFunction.o
>
> ALL_OBJECTS=$(PLUGIN_OBJECTS)
> ALL_TARGETS=$(PLUGIN) $(TEST_FILE)
>
> CPP_OPTIONS+=$(CPPFLAGS) $(shell $(LLVM_CONFIG) --cppflags) -MD -MP
-I$(SRC_DIR)
>
> LD_OPTIONS+=$(LDFLAGS) $(shell $(LLVM_CONFIG) --ldflags)
>
> all: $(ALL_TARGETS)
>
> %.o : $(SRC_DIR)/%.cpp
>      @echo Compiling $*.cpp
>      $(QUIET)$(CXX) -c $(CPP_OPTIONS) $(CXXFLAGS) $<
>
> $(PLUGIN): $(PLUGIN_OBJECTS)
>      @echo Linking $@
>      $(QUIET)$(CXX) -o $@ $(LOADABLE_MODULE_OPTIONS) $(CXXFLAGS)
$(LD_OPTIONS)
> $(PLUGIN_OBJECTS)
>
> RUN_FLAGS=-duplicateFunction
>
> $(TEST_FILE): $(TEST_C)
>      clang -g -O3 -S -emit-llvm $^
> #    clang -g -O0 -S -emit-llvm $^
> #     clang -O0 -S -emit-llvm $^
> run:
>      opt -load ./$(PLUGIN) $(RUN_FLAGS) < $(TEST_FILE) > /dev/null
2> after.s
> #    opt -load ./$(PLUGIN) $(RUN_FLAGS) < $(TEST_FILE) > /dev/null
>
> clean:
>      $(QUIET)rm -f $(ALL_OBJECTS) *.d $(PLUGIN) $(TEST_FILE)
>
>
> -include $(ALL_OBJECTS:.o=.d)
>
>
>
>
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

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