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//===- ReduceArguments.cpp - Specialized Delta Pass -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements a function which calls the Generic Delta pass in order
// to reduce uninteresting Arguments from declared and defined functions.
//
//===----------------------------------------------------------------------===//
#include "ReduceArguments.h"
#include "Delta.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/Intrinsics.h"
#include <set>
#include <vector>
using namespace llvm;
/// Goes over OldF calls and replaces them with a call to NewF
static void replaceFunctionCalls(Function &OldF, Function &NewF,
const std::set<int> &ArgIndexesToKeep) {
const auto &Users = OldF.users();
for (auto I = Users.begin(), E = Users.end(); I != E; )
if (auto *CI = dyn_cast<CallInst>(*I++)) {
// Skip uses in call instructions where OldF isn't the called function
// (e.g. if OldF is an argument of the call).
if (CI->getCalledFunction() != &OldF)
continue;
SmallVector<Value *, 8> Args;
for (auto ArgI = CI->arg_begin(), E = CI->arg_end(); ArgI != E; ++ArgI)
if (ArgIndexesToKeep.count(ArgI - CI->arg_begin()))
Args.push_back(*ArgI);
CallInst *NewCI = CallInst::Create(&NewF, Args);
NewCI->setCallingConv(NewF.getCallingConv());
if (!CI->use_empty())
CI->replaceAllUsesWith(NewCI);
ReplaceInstWithInst(CI, NewCI);
}
}
/// Returns whether or not this function should be considered a candidate for
/// argument removal. Currently, functions with no arguments and intrinsics are
/// not considered. Intrinsics aren't considered because their signatures are
/// fixed.
static bool shouldRemoveArguments(const Function &F) {
return !F.arg_empty() && !F.isIntrinsic();
}
/// Removes out-of-chunk arguments from functions, and modifies their calls
/// accordingly. It also removes allocations of out-of-chunk arguments.
static void extractArgumentsFromModule(Oracle &O, Module &Program) {
std::vector<Argument *> InitArgsToKeep;
std::vector<Function *> Funcs;
// Get inside-chunk arguments, as well as their parent function
for (auto &F : Program)
if (shouldRemoveArguments(F)) {
Funcs.push_back(&F);
for (auto &A : F.args())
if (O.shouldKeep())
InitArgsToKeep.push_back(&A);
}
// We create a vector first, then convert it to a set, so that we don't have
// to pay the cost of rebalancing the set frequently if the order we insert
// the elements doesn't match the order they should appear inside the set.
std::set<Argument *> ArgsToKeep(InitArgsToKeep.begin(), InitArgsToKeep.end());
for (auto *F : Funcs) {
ValueToValueMapTy VMap;
std::vector<WeakVH> InstToDelete;
for (auto &A : F->args())
if (!ArgsToKeep.count(&A)) {
// By adding undesired arguments to the VMap, CloneFunction will remove
// them from the resulting Function
VMap[&A] = UndefValue::get(A.getType());
for (auto *U : A.users())
if (auto *I = dyn_cast<Instruction>(*&U))
InstToDelete.push_back(I);
}
// Delete any (unique) instruction that uses the argument
for (Value *V : InstToDelete) {
if (!V)
continue;
auto *I = cast<Instruction>(V);
I->replaceAllUsesWith(UndefValue::get(I->getType()));
if (!I->isTerminator())
I->eraseFromParent();
}
// No arguments to reduce
if (VMap.empty())
continue;
std::set<int> ArgIndexesToKeep;
for (auto &Arg : enumerate(F->args()))
if (ArgsToKeep.count(&Arg.value()))
ArgIndexesToKeep.insert(Arg.index());
auto *ClonedFunc = CloneFunction(F, VMap);
// In order to preserve function order, we move Clone after old Function
ClonedFunc->removeFromParent();
Program.getFunctionList().insertAfter(F->getIterator(), ClonedFunc);
replaceFunctionCalls(*F, *ClonedFunc, ArgIndexesToKeep);
// Rename Cloned Function to Old's name
std::string FName = std::string(F->getName());
F->replaceAllUsesWith(ConstantExpr::getBitCast(ClonedFunc, F->getType()));
F->eraseFromParent();
ClonedFunc->setName(FName);
}
}
void llvm::reduceArgumentsDeltaPass(TestRunner &Test) {
outs() << "*** Reducing Arguments...\n";
runDeltaPass(Test, extractArgumentsFromModule);
}
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