maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp

702 lines
28 KiB
C++
Raw Blame History

//===-- ArgumentPromotion.cpp - Promote by-reference arguments ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass promotes "by reference" arguments to be "by value" arguments. In
// practice, this means looking for internal functions that have pointer
// arguments. If it can prove, through the use of alias analysis, that an
// argument is *only* loaded, then it can pass the value into the function
// instead of the address of the value. This can cause recursive simplification
// of code and lead to the elimination of allocas (especially in C++ template
// code like the STL).
//
// This pass also handles aggregate arguments that are passed into a function,
// scalarizing them if the elements of the aggregate are only loaded. Note that
// it refuses to scalarize aggregates which would require passing in more than
// three operands to the function, because passing thousands of operands for a
// large array or structure is unprofitable!
//
// Note that this transformation could also be done for arguments that are only
// stored to (returning the value instead), but does not currently. This case
// would be best handled when and if LLVM begins supporting multiple return
// values from functions.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "argpromotion"
#include "llvm/Transforms/IPO.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/CallGraphSCCPass.h"
#include "llvm/Instructions.h"
#include "llvm/ParameterAttributes.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Compiler.h"
#include <set>
using namespace llvm;
STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted");
STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted");
STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted");
STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated");
namespace {
/// ArgPromotion - The 'by reference' to 'by value' argument promotion pass.
///
struct VISIBILITY_HIDDEN ArgPromotion : public CallGraphSCCPass {
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<AliasAnalysis>();
AU.addRequired<TargetData>();
CallGraphSCCPass::getAnalysisUsage(AU);
}
virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC);
static char ID; // Pass identification, replacement for typeid
ArgPromotion() : CallGraphSCCPass((intptr_t)&ID) {}
private:
bool PromoteArguments(CallGraphNode *CGN);
bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
Function *DoPromotion(Function *F,
SmallPtrSet<Argument*, 8> &ArgsToPromote,
SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
};
char ArgPromotion::ID = 0;
RegisterPass<ArgPromotion> X("argpromotion",
"Promote 'by reference' arguments to scalars");
}
Pass *llvm::createArgumentPromotionPass() {
return new ArgPromotion();
}
bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
bool Changed = false, LocalChange;
do { // Iterate until we stop promoting from this SCC.
LocalChange = false;
// Attempt to promote arguments from all functions in this SCC.
for (unsigned i = 0, e = SCC.size(); i != e; ++i)
LocalChange |= PromoteArguments(SCC[i]);
Changed |= LocalChange; // Remember that we changed something.
} while (LocalChange);
return Changed;
}
/// PromoteArguments - This method checks the specified function to see if there
/// are any promotable arguments and if it is safe to promote the function (for
/// example, all callers are direct). If safe to promote some arguments, it
/// calls the DoPromotion method.
///
bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
Function *F = CGN->getFunction();
// Make sure that it is local to this module.
if (!F || !F->hasInternalLinkage()) return false;
// First check: see if there are any pointer arguments! If not, quick exit.
SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
unsigned ArgNo = 0;
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
I != E; ++I, ++ArgNo)
if (isa<PointerType>(I->getType()))
PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
if (PointerArgs.empty()) return false;
// Second check: make sure that all callers are direct callers. We can't
// transform functions that have indirect callers.
for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
UI != E; ++UI) {
CallSite CS = CallSite::get(*UI);
if (!CS.getInstruction()) // "Taking the address" of the function
return false;
// Ensure that this call site is CALLING the function, not passing it as
// an argument.
if (UI.getOperandNo() != 0)
return false;
}
// Check to see which arguments are promotable. If an argument is promotable,
// add it to ArgsToPromote.
SmallPtrSet<Argument*, 8> ArgsToPromote;
SmallPtrSet<Argument*, 8> ByValArgsToTransform;
for (unsigned i = 0; i != PointerArgs.size(); ++i) {
bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, ParamAttr::ByVal);
// If this is a byval argument, and if the aggregate type is small, just
// pass the elements, which is always safe.
Argument *PtrArg = PointerArgs[i].first;
if (isByVal) {
const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
if (const StructType *STy = dyn_cast<StructType>(AgTy))
if (STy->getNumElements() <= 3) {
// If all the elements are first class types, we can promote it.
bool AllSimple = true;
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
if (!STy->getElementType(i)->isFirstClassType()) {
AllSimple = false;
break;
}
// Safe to transform, don't even bother trying to "promote" it.
// Passing the elements as a scalar will allow scalarrepl to hack on
// the new alloca we introduce.
if (AllSimple) {
ByValArgsToTransform.insert(PtrArg);
continue;
}
}
}
// Otherwise, see if we can promote the pointer to its value.
if (isSafeToPromoteArgument(PtrArg, isByVal))
ArgsToPromote.insert(PtrArg);
}
// No promotable pointer arguments.
if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false;
Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
// Update the call graph to know that the function has been transformed.
getAnalysis<CallGraph>().changeFunction(F, NewF);
return true;
}
/// IsAlwaysValidPointer - Return true if the specified pointer is always legal
/// to load.
static bool IsAlwaysValidPointer(Value *V) {
if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
return IsAlwaysValidPointer(GEP->getOperand(0));
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
if (CE->getOpcode() == Instruction::GetElementPtr)
return IsAlwaysValidPointer(CE->getOperand(0));
return false;
}
/// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
/// all callees pass in a valid pointer for the specified function argument.
static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
Function *Callee = Arg->getParent();
unsigned ArgNo = std::distance(Callee->arg_begin(),
Function::arg_iterator(Arg));
// Look at all call sites of the function. At this pointer we know we only
// have direct callees.
for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
UI != E; ++UI) {
CallSite CS = CallSite::get(*UI);
assert(CS.getInstruction() && "Should only have direct calls!");
if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
return false;
}
return true;
}
/// isSafeToPromoteArgument - As you might guess from the name of this method,
/// it checks to see if it is both safe and useful to promote the argument.
/// This method limits promotion of aggregates to only promote up to three
/// elements of the aggregate in order to avoid exploding the number of
/// arguments passed in.
bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
// We can only promote this argument if all of the uses are loads, or are GEP
// instructions (with constant indices) that are subsequently loaded.
// We can also only promote the load if we can guarantee that it will happen.
// Promoting a load causes the load to be unconditionally executed in the
// caller, so we can't turn a conditional load into an unconditional load in
// general.
bool SafeToUnconditionallyLoad = false;
if (isByVal) // ByVal arguments are always safe to load from.
SafeToUnconditionallyLoad = true;
BasicBlock *EntryBlock = Arg->getParent()->begin();
SmallVector<LoadInst*, 16> Loads;
std::vector<SmallVector<ConstantInt*, 8> > GEPIndices;
for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
UI != E; ++UI)
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
if (LI->isVolatile()) return false; // Don't hack volatile loads
Loads.push_back(LI);
// If this load occurs in the entry block, then the pointer is
// unconditionally loaded.
SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock;
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
if (GEP->use_empty()) {
// Dead GEP's cause trouble later. Just remove them if we run into
// them.
getAnalysis<AliasAnalysis>().deleteValue(GEP);
GEP->eraseFromParent();
return isSafeToPromoteArgument(Arg, isByVal);
}
// Ensure that all of the indices are constants.
SmallVector<ConstantInt*, 8> Operands;
for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
if (ConstantInt *C = dyn_cast<ConstantInt>(GEP->getOperand(i)))
Operands.push_back(C);
else
return false; // Not a constant operand GEP!
// Ensure that the only users of the GEP are load instructions.
for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
UI != E; ++UI)
if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
if (LI->isVolatile()) return false; // Don't hack volatile loads
Loads.push_back(LI);
// If this load occurs in the entry block, then the pointer is
// unconditionally loaded.
SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock;
} else {
return false;
}
// See if there is already a GEP with these indices. If not, check to
// make sure that we aren't promoting too many elements. If so, nothing
// to do.
if (std::find(GEPIndices.begin(), GEPIndices.end(), Operands) ==
GEPIndices.end()) {
if (GEPIndices.size() == 3) {
DOUT << "argpromotion disable promoting argument '"
<< Arg->getName() << "' because it would require adding more "
<< "than 3 arguments to the function.\n";
// We limit aggregate promotion to only promoting up to three elements
// of the aggregate.
return false;
}
GEPIndices.push_back(Operands);
}
} else {
return false; // Not a load or a GEP.
}
if (Loads.empty()) return true; // No users, this is a dead argument.
// If we decide that we want to promote this argument, the value is going to
// be unconditionally loaded in all callees. This is only safe to do if the
// pointer was going to be unconditionally loaded anyway (i.e. there is a load
// of the pointer in the entry block of the function) or if we can prove that
// all pointers passed in are always to legal locations (for example, no null
// pointers are passed in, no pointers to free'd memory, etc).
if (!SafeToUnconditionallyLoad &&
!AllCalleesPassInValidPointerForArgument(Arg))
return false; // Cannot prove that this is safe!!
// Okay, now we know that the argument is only used by load instructions and
// it is safe to unconditionally load the pointer. Use alias analysis to
// check to see if the pointer is guaranteed to not be modified from entry of
// the function to each of the load instructions.
// Because there could be several/many load instructions, remember which
// blocks we know to be transparent to the load.
SmallPtrSet<BasicBlock*, 16> TranspBlocks;
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
TargetData &TD = getAnalysis<TargetData>();
for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
// Check to see if the load is invalidated from the start of the block to
// the load itself.
LoadInst *Load = Loads[i];
BasicBlock *BB = Load->getParent();
const PointerType *LoadTy =
cast<PointerType>(Load->getOperand(0)->getType());
unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType());
if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
return false; // Pointer is invalidated!
// Now check every path from the entry block to the load for transparency.
// To do this, we perform a depth first search on the inverse CFG from the
// loading block.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
I = idf_ext_begin(*PI, TranspBlocks),
E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
if (AA.canBasicBlockModify(**I, Arg, LoadSize))
return false;
}
// If the path from the entry of the function to each load is free of
// instructions that potentially invalidate the load, we can make the
// transformation!
return true;
}
namespace {
/// GEPIdxComparator - Provide a strong ordering for GEP indices. All Value*
/// elements are instances of ConstantInt.
///
struct GEPIdxComparator {
bool operator()(const std::vector<Value*> &LHS,
const std::vector<Value*> &RHS) const {
unsigned idx = 0;
for (; idx < LHS.size() && idx < RHS.size(); ++idx) {
if (LHS[idx] != RHS[idx]) {
return cast<ConstantInt>(LHS[idx])->getZExtValue() <
cast<ConstantInt>(RHS[idx])->getZExtValue();
}
}
// Return less than if we ran out of stuff in LHS and we didn't run out of
// stuff in RHS.
return idx == LHS.size() && idx != RHS.size();
}
};
}
/// DoPromotion - This method actually performs the promotion of the specified
/// arguments, and returns the new function. At this point, we know that it's
/// safe to do so.
Function *ArgPromotion::DoPromotion(Function *F,
SmallPtrSet<Argument*, 8> &ArgsToPromote,
SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
// Start by computing a new prototype for the function, which is the same as
// the old function, but has modified arguments.
const FunctionType *FTy = F->getFunctionType();
std::vector<const Type*> Params;
typedef std::set<std::vector<Value*>, GEPIdxComparator> ScalarizeTable;
// ScalarizedElements - If we are promoting a pointer that has elements
// accessed out of it, keep track of which elements are accessed so that we
// can add one argument for each.
//
// Arguments that are directly loaded will have a zero element value here, to
// handle cases where there are both a direct load and GEP accesses.
//
std::map<Argument*, ScalarizeTable> ScalarizedElements;
// OriginalLoads - Keep track of a representative load instruction from the
// original function so that we can tell the alias analysis implementation
// what the new GEP/Load instructions we are inserting look like.
std::map<std::vector<Value*>, LoadInst*> OriginalLoads;
// ParamAttrs - Keep track of the parameter attributes for the arguments
// that we are *not* promoting. For the ones that we do promote, the parameter
// attributes are lost
ParamAttrsVector ParamAttrsVec;
const ParamAttrsList *PAL = F->getParamAttrs();
// Add any return attributes.
if (unsigned attrs = PAL ? PAL->getParamAttrs(0) : 0)
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
unsigned ArgIndex = 1;
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
++I, ++ArgIndex) {
if (ByValArgsToTransform.count(I)) {
// Just add all the struct element types.
const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
const StructType *STy = cast<StructType>(AgTy);
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
Params.push_back(STy->getElementType(i));
++NumByValArgsPromoted;
} else if (!ArgsToPromote.count(I)) {
Params.push_back(I->getType());
if (unsigned attrs = PAL ? PAL->getParamAttrs(ArgIndex) : 0)
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), attrs));
} else if (I->use_empty()) {
++NumArgumentsDead;
} else {
// Okay, this is being promoted. Check to see if there are any GEP uses
// of the argument.
ScalarizeTable &ArgIndices = ScalarizedElements[I];
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
++UI) {
Instruction *User = cast<Instruction>(*UI);
assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
std::vector<Value*> Indices(User->op_begin()+1, User->op_end());
ArgIndices.insert(Indices);
LoadInst *OrigLoad;
if (LoadInst *L = dyn_cast<LoadInst>(User))
OrigLoad = L;
else
OrigLoad = cast<LoadInst>(User->use_back());
OriginalLoads[Indices] = OrigLoad;
}
// Add a parameter to the function for each element passed in.
for (ScalarizeTable::iterator SI = ArgIndices.begin(),
E = ArgIndices.end(); SI != E; ++SI)
Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
SI->begin(),
SI->end()));
if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
++NumArgumentsPromoted;
else
++NumAggregatesPromoted;
}
}
const Type *RetTy = FTy->getReturnType();
// Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
// have zero fixed arguments.
bool ExtraArgHack = false;
if (Params.empty() && FTy->isVarArg()) {
ExtraArgHack = true;
Params.push_back(Type::Int32Ty);
}
// Construct the new function type using the new arguments.
FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
// Create the new function body and insert it into the module...
Function *NF = new Function(NFTy, F->getLinkage(), F->getName());
NF->setCallingConv(F->getCallingConv());
// Recompute the parameter attributes list based on the new arguments for
// the function.
NF->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
ParamAttrsVec.clear(); PAL = 0;
if (F->hasCollector())
NF->setCollector(F->getCollector());
F->getParent()->getFunctionList().insert(F, NF);
// Get the alias analysis information that we need to update to reflect our
// changes.
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// Loop over all of the callers of the function, transforming the call sites
// to pass in the loaded pointers.
//
SmallVector<Value*, 16> Args;
while (!F->use_empty()) {
CallSite CS = CallSite::get(F->use_back());
Instruction *Call = CS.getInstruction();
PAL = CS.getParamAttrs();
// Add any return attributes.
if (unsigned attrs = PAL ? PAL->getParamAttrs(0) : 0)
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
// Loop over the operands, inserting GEP and loads in the caller as
// appropriate.
CallSite::arg_iterator AI = CS.arg_begin();
ArgIndex = 1;
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
I != E; ++I, ++AI, ++ArgIndex)
if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
Args.push_back(*AI); // Unmodified argument
if (unsigned Attrs = PAL ? PAL->getParamAttrs(ArgIndex) : 0)
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
} else if (ByValArgsToTransform.count(I)) {
// Emit a GEP and load for each element of the struct.
const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
const StructType *STy = cast<StructType>(AgTy);
Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
Value *Idx = new GetElementPtrInst(*AI, Idxs, Idxs+2,
(*AI)->getName()+"."+utostr(i),
Call);
// TODO: Tell AA about the new values?
Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
}
} else if (!I->use_empty()) {
// Non-dead argument: insert GEPs and loads as appropriate.
ScalarizeTable &ArgIndices = ScalarizedElements[I];
for (ScalarizeTable::iterator SI = ArgIndices.begin(),
E = ArgIndices.end(); SI != E; ++SI) {
Value *V = *AI;
LoadInst *OrigLoad = OriginalLoads[*SI];
if (!SI->empty()) {
V = new GetElementPtrInst(V, SI->begin(), SI->end(),
V->getName()+".idx", Call);
AA.copyValue(OrigLoad->getOperand(0), V);
}
Args.push_back(new LoadInst(V, V->getName()+".val", Call));
AA.copyValue(OrigLoad, Args.back());
}
}
if (ExtraArgHack)
Args.push_back(Constant::getNullValue(Type::Int32Ty));
// Push any varargs arguments on the list
for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
Args.push_back(*AI);
if (unsigned Attrs = PAL ? PAL->getParamAttrs(ArgIndex) : 0)
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
}
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
Args.begin(), Args.end(), "", Call);
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
cast<InvokeInst>(New)->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
} else {
New = new CallInst(NF, Args.begin(), Args.end(), "", Call);
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
cast<CallInst>(New)->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
if (cast<CallInst>(Call)->isTailCall())
cast<CallInst>(New)->setTailCall();
}
Args.clear();
ParamAttrsVec.clear();
// Update the alias analysis implementation to know that we are replacing
// the old call with a new one.
AA.replaceWithNewValue(Call, New);
if (!Call->use_empty()) {
Call->replaceAllUsesWith(New);
New->takeName(Call);
}
// Finally, remove the old call from the program, reducing the use-count of
// F.
Call->eraseFromParent();
}
// Since we have now created 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());
// Loop over the argument list, transfering uses of the old arguments over to
// the new arguments, also transfering over the names as well.
//
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
I2 = NF->arg_begin(); I != E; ++I) {
if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
// If this is an unmodified argument, move the name and users over to the
// new version.
I->replaceAllUsesWith(I2);
I2->takeName(I);
AA.replaceWithNewValue(I, I2);
++I2;
continue;
}
if (ByValArgsToTransform.count(I)) {
// In the callee, we create an alloca, and store each of the new incoming
// arguments into the alloca.
Instruction *InsertPt = NF->begin()->begin();
// Just add all the struct element types.
const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
const StructType *STy = cast<StructType>(AgTy);
Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
Value *Idx = new GetElementPtrInst(TheAlloca, Idxs, Idxs+2,
TheAlloca->getName()+"."+utostr(i),
InsertPt);
I2->setName(I->getName()+"."+utostr(i));
new StoreInst(I2++, Idx, InsertPt);
}
// Anything that used the arg should now use the alloca.
I->replaceAllUsesWith(TheAlloca);
TheAlloca->takeName(I);
AA.replaceWithNewValue(I, TheAlloca);
continue;
}
if (I->use_empty()) {
AA.deleteValue(I);
continue;
}
// Otherwise, if we promoted this argument, then all users are load
// instructions, and all loads should be using the new argument that we
// added.
ScalarizeTable &ArgIndices = ScalarizedElements[I];
while (!I->use_empty()) {
if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
assert(ArgIndices.begin()->empty() &&
"Load element should sort to front!");
I2->setName(I->getName()+".val");
LI->replaceAllUsesWith(I2);
AA.replaceWithNewValue(LI, I2);
LI->eraseFromParent();
DOUT << "*** Promoted load of argument '" << I->getName()
<< "' in function '" << F->getName() << "'\n";
} else {
GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
std::vector<Value*> Operands(GEP->op_begin()+1, GEP->op_end());
Function::arg_iterator TheArg = I2;
for (ScalarizeTable::iterator It = ArgIndices.begin();
*It != Operands; ++It, ++TheArg) {
assert(It != ArgIndices.end() && "GEP not handled??");
}
std::string NewName = I->getName();
for (unsigned i = 0, e = Operands.size(); i != e; ++i)
if (ConstantInt *CI = dyn_cast<ConstantInt>(Operands[i]))
NewName += "." + CI->getValue().toStringUnsigned(10);
else
NewName += ".x";
TheArg->setName(NewName+".val");
DOUT << "*** Promoted agg argument '" << TheArg->getName()
<< "' of function '" << F->getName() << "'\n";
// All of the uses must be load instructions. Replace them all with
// the argument specified by ArgNo.
while (!GEP->use_empty()) {
LoadInst *L = cast<LoadInst>(GEP->use_back());
L->replaceAllUsesWith(TheArg);
AA.replaceWithNewValue(L, TheArg);
L->eraseFromParent();
}
AA.deleteValue(GEP);
GEP->eraseFromParent();
}
}
// Increment I2 past all of the arguments added for this promoted pointer.
for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
++I2;
}
// Notify the alias analysis implementation that we inserted a new argument.
if (ExtraArgHack)
AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin());
// Tell the alias analysis that the old function is about to disappear.
AA.replaceWithNewValue(F, NF);
// Now that the old function is dead, delete it.
F->eraseFromParent();
return NF;
}
Reference in New Issue View Git Blame Copy Permalink