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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 "Utils.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/FMF.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Operator.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include <set>
#include <vector>
using namespace llvm;
static bool callingConvRequiresArgument(const Function &F,
const Argument &Arg) {
switch (F.getCallingConv()) {
case CallingConv::X86_INTR:
// If there are any arguments, the first one must by byval.
return Arg.getArgNo() == 0 && F.arg_size() != 1;
default:
return false;
}
llvm_unreachable("covered calling conv switch");
}
/// Goes over OldF calls and replaces them with a call to NewF
static void replaceFunctionCalls(Function &OldF, Function &NewF,
const std::set<int> &ArgIndexesToKeep) {
LLVMContext &Ctx = OldF.getContext();
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;
SmallVector<AttrBuilder, 8> ArgAttrs;
for (auto ArgI = CI->arg_begin(), E = CI->arg_end(); ArgI != E; ++ArgI) {
unsigned ArgIdx = ArgI - CI->arg_begin();
if (ArgIndexesToKeep.count(ArgIdx)) {
Args.push_back(*ArgI);
ArgAttrs.emplace_back(Ctx, CI->getParamAttributes(ArgIdx));
}
}
SmallVector<OperandBundleDef, 2> OpBundles;
CI->getOperandBundlesAsDefs(OpBundles);
CallInst *NewCI = CallInst::Create(&NewF, Args, OpBundles);
NewCI->setCallingConv(CI->getCallingConv());
AttrBuilder CallSiteAttrs(Ctx, CI->getAttributes().getFnAttrs());
NewCI->setAttributes(
AttributeList::get(Ctx, AttributeList::FunctionIndex, CallSiteAttrs));
NewCI->addRetAttrs(AttrBuilder(Ctx, CI->getRetAttributes()));
unsigned AttrIdx = 0;
for (auto ArgI = NewCI->arg_begin(), E = NewCI->arg_end(); ArgI != E;
++ArgI, ++AttrIdx)
NewCI->addParamAttrs(AttrIdx, ArgAttrs[AttrIdx]);
if (auto *FPOp = dyn_cast<FPMathOperator>(NewCI))
cast<Instruction>(FPOp)->setFastMathFlags(CI->getFastMathFlags());
NewCI->copyMetadata(*CI);
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();
}
static bool allFuncUsersRewritable(const Function &F) {
for (const Use &U : F.uses()) {
const CallBase *CB = dyn_cast<CallBase>(U.getUser());
if (!CB || !CB->isCallee(&U))
continue;
// TODO: Handle all CallBase cases.
if (!isa<CallInst>(CB))
return false;
}
return true;
}
/// Removes out-of-chunk arguments from functions, and modifies their calls
/// accordingly. It also removes allocations of out-of-chunk arguments.
void llvm::reduceArgumentsDeltaPass(Oracle &O, ReducerWorkItem &WorkItem) {
Module &Program = WorkItem.getModule();
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))
continue;
if (!allFuncUsersRewritable(F))
continue;
Funcs.push_back(&F);
for (auto &A : F.args()) {
if (callingConvRequiresArgument(F, A) || 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] = getDefaultValue(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(getDefaultValue(I->getType()));
if (!I->isTerminator())
I->eraseFromParent();
}
// No arguments to reduce
if (VMap.empty())
continue;
std::set<int> ArgIndexesToKeep;
for (const auto &[Index, Arg] : enumerate(F->args()))
if (ArgsToKeep.count(&Arg))
ArgIndexesToKeep.insert(Index);
auto *ClonedFunc = CloneFunction(F, VMap);
// In order to preserve function order, we move Clone after old Function
ClonedFunc->takeName(F);
ClonedFunc->removeFromParent();
Program.getFunctionList().insertAfter(F->getIterator(), ClonedFunc);
replaceFunctionCalls(*F, *ClonedFunc, ArgIndexesToKeep);
F->replaceAllUsesWith(ClonedFunc);
F->eraseFromParent();
}
}
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