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llvm-project/llvm/lib/Transforms/Scalar/ScalarReplAggregates.cpp

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//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This transformation implements the well known scalar replacement of
// aggregates transformation. This xform breaks up alloca instructions of
// aggregate type (structure or array) into individual alloca instructions for
// each member (if possible). Then, if possible, it transforms the individual
// alloca instructions into nice clean scalar SSA form.
//
// This combines a simple SRoA algorithm with the Mem2Reg algorithm because
// often interact, especially for C++ programs. As such, iterating between
// SRoA, then Mem2Reg until we run out of things to promote works well.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "scalarrepl"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Pass.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
using namespace llvm;
STATISTIC(NumReplaced, "Number of allocas broken up");
STATISTIC(NumPromoted, "Number of allocas promoted");
STATISTIC(NumConverted, "Number of aggregates converted to scalar");
namespace {
struct VISIBILITY_HIDDEN SROA : public FunctionPass {
bool runOnFunction(Function &F);
bool performScalarRepl(Function &F);
bool performPromotion(Function &F);
// getAnalysisUsage - This pass does not require any passes, but we know it
// will not alter the CFG, so say so.
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTree>();
AU.addRequired<DominanceFrontier>();
AU.addRequired<TargetData>();
AU.setPreservesCFG();
}
private:
int isSafeElementUse(Value *Ptr);
int isSafeUseOfAllocation(Instruction *User);
int isSafeAllocaToScalarRepl(AllocationInst *AI);
void CanonicalizeAllocaUsers(AllocationInst *AI);
AllocaInst *AddNewAlloca(Function &F, const Type *Ty, AllocationInst *Base);
const Type *CanConvertToScalar(Value *V, bool &IsNotTrivial);
void ConvertToScalar(AllocationInst *AI, const Type *Ty);
void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset);
};
RegisterPass<SROA> X("scalarrepl", "Scalar Replacement of Aggregates");
}
// Public interface to the ScalarReplAggregates pass
FunctionPass *llvm::createScalarReplAggregatesPass() { return new SROA(); }
bool SROA::runOnFunction(Function &F) {
bool Changed = performPromotion(F);
while (1) {
bool LocalChange = performScalarRepl(F);
if (!LocalChange) break; // No need to repromote if no scalarrepl
Changed = true;
LocalChange = performPromotion(F);
if (!LocalChange) break; // No need to re-scalarrepl if no promotion
}
return Changed;
}
bool SROA::performPromotion(Function &F) {
std::vector<AllocaInst*> Allocas;
const TargetData &TD = getAnalysis<TargetData>();
DominatorTree &DT = getAnalysis<DominatorTree>();
DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
bool Changed = false;
while (1) {
Allocas.clear();
// Find allocas that are safe to promote, by looking at all instructions in
// the entry node
for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
if (isAllocaPromotable(AI, TD))
Allocas.push_back(AI);
if (Allocas.empty()) break;
PromoteMemToReg(Allocas, DT, DF, TD);
NumPromoted += Allocas.size();
Changed = true;
}
return Changed;
}
// performScalarRepl - This algorithm is a simple worklist driven algorithm,
// which runs on all of the malloc/alloca instructions in the function, removing
// them if they are only used by getelementptr instructions.
//
bool SROA::performScalarRepl(Function &F) {
std::vector<AllocationInst*> WorkList;
// Scan the entry basic block, adding any alloca's and mallocs to the worklist
BasicBlock &BB = F.getEntryBlock();
for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
if (AllocationInst *A = dyn_cast<AllocationInst>(I))
WorkList.push_back(A);
// Process the worklist
bool Changed = false;
while (!WorkList.empty()) {
AllocationInst *AI = WorkList.back();
WorkList.pop_back();
// Handle dead allocas trivially. These can be formed by SROA'ing arrays
// with unused elements.
if (AI->use_empty()) {
AI->eraseFromParent();
continue;
}
// If we can turn this aggregate value (potentially with casts) into a
// simple scalar value that can be mem2reg'd into a register value.
bool IsNotTrivial = false;
if (const Type *ActualType = CanConvertToScalar(AI, IsNotTrivial))
if (IsNotTrivial && ActualType != Type::VoidTy) {
ConvertToScalar(AI, ActualType);
Changed = true;
continue;
}
// We cannot transform the allocation instruction if it is an array
// allocation (allocations OF arrays are ok though), and an allocation of a
// scalar value cannot be decomposed at all.
//
if (AI->isArrayAllocation() ||
(!isa<StructType>(AI->getAllocatedType()) &&
!isa<ArrayType>(AI->getAllocatedType()))) continue;
// Check that all of the users of the allocation are capable of being
// transformed.
switch (isSafeAllocaToScalarRepl(AI)) {
default: assert(0 && "Unexpected value!");
case 0: // Not safe to scalar replace.
continue;
case 1: // Safe, but requires cleanup/canonicalizations first
CanonicalizeAllocaUsers(AI);
case 3: // Safe to scalar replace.
break;
}
DOUT << "Found inst to xform: " << *AI;
Changed = true;
std::vector<AllocaInst*> ElementAllocas;
if (const StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
ElementAllocas.reserve(ST->getNumContainedTypes());
for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
AllocaInst *NA = new AllocaInst(ST->getContainedType(i), 0,
AI->getAlignment(),
AI->getName() + "." + utostr(i), AI);
ElementAllocas.push_back(NA);
WorkList.push_back(NA); // Add to worklist for recursive processing
}
} else {
const ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
ElementAllocas.reserve(AT->getNumElements());
const Type *ElTy = AT->getElementType();
for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
AllocaInst *NA = new AllocaInst(ElTy, 0, AI->getAlignment(),
AI->getName() + "." + utostr(i), AI);
ElementAllocas.push_back(NA);
WorkList.push_back(NA); // Add to worklist for recursive processing
}
}
// Now that we have created the alloca instructions that we want to use,
// expand the getelementptr instructions to use them.
//
while (!AI->use_empty()) {
Instruction *User = cast<Instruction>(AI->use_back());
GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
// We now know that the GEP is of the form: GEP <ptr>, 0, <cst>
unsigned Idx =
(unsigned)cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
assert(Idx < ElementAllocas.size() && "Index out of range?");
AllocaInst *AllocaToUse = ElementAllocas[Idx];
Value *RepValue;
if (GEPI->getNumOperands() == 3) {
// Do not insert a new getelementptr instruction with zero indices, only
// to have it optimized out later.
RepValue = AllocaToUse;
} else {
// We are indexing deeply into the structure, so we still need a
// getelement ptr instruction to finish the indexing. This may be
// expanded itself once the worklist is rerun.
//
std::string OldName = GEPI->getName(); // Steal the old name.
std::vector<Value*> NewArgs;
NewArgs.push_back(Constant::getNullValue(Type::Int32Ty));
NewArgs.insert(NewArgs.end(), GEPI->op_begin()+3, GEPI->op_end());
GEPI->setName("");
RepValue = new GetElementPtrInst(AllocaToUse, NewArgs, OldName, GEPI);
}
// Move all of the users over to the new GEP.
GEPI->replaceAllUsesWith(RepValue);
// Delete the old GEP
GEPI->eraseFromParent();
}
// Finally, delete the Alloca instruction
AI->eraseFromParent();
NumReplaced++;
}
return Changed;
}
/// isSafeElementUse - Check to see if this use is an allowed use for a
/// getelementptr instruction of an array aggregate allocation.
///
int SROA::isSafeElementUse(Value *Ptr) {
for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
I != E; ++I) {
Instruction *User = cast<Instruction>(*I);
switch (User->getOpcode()) {
case Instruction::Load: break;
case Instruction::Store:
// Store is ok if storing INTO the pointer, not storing the pointer
if (User->getOperand(0) == Ptr) return 0;
break;
case Instruction::GetElementPtr: {
GetElementPtrInst *GEP = cast<GetElementPtrInst>(User);
if (GEP->getNumOperands() > 1) {
if (!isa<Constant>(GEP->getOperand(1)) ||
!cast<Constant>(GEP->getOperand(1))->isNullValue())
return 0; // Using pointer arithmetic to navigate the array...
}
if (!isSafeElementUse(GEP)) return 0;
break;
}
default:
DOUT << " Transformation preventing inst: " << *User;
return 0;
}
}
return 3; // All users look ok :)
}
/// AllUsersAreLoads - Return true if all users of this value are loads.
static bool AllUsersAreLoads(Value *Ptr) {
for (Value::use_iterator I = Ptr->use_begin(), E = Ptr->use_end();
I != E; ++I)
if (cast<Instruction>(*I)->getOpcode() != Instruction::Load)
return false;
return true;
}
/// isSafeUseOfAllocation - Check to see if this user is an allowed use for an
/// aggregate allocation.
///
int SROA::isSafeUseOfAllocation(Instruction *User) {
if (!isa<GetElementPtrInst>(User)) return 0;
GetElementPtrInst *GEPI = cast<GetElementPtrInst>(User);
gep_type_iterator I = gep_type_begin(GEPI), E = gep_type_end(GEPI);
// The GEP is not safe to transform if not of the form "GEP <ptr>, 0, <cst>".
if (I == E ||
I.getOperand() != Constant::getNullValue(I.getOperand()->getType()))
return 0;
++I;
if (I == E) return 0; // ran out of GEP indices??
// If this is a use of an array allocation, do a bit more checking for sanity.
if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
uint64_t NumElements = AT->getNumElements();
if (isa<ConstantInt>(I.getOperand())) {
// Check to make sure that index falls within the array. If not,
// something funny is going on, so we won't do the optimization.
//
if (cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue() >= NumElements)
return 0;
// We cannot scalar repl this level of the array unless any array
// sub-indices are in-range constants. In particular, consider:
// A[0][i]. We cannot know that the user isn't doing invalid things like
// allowing i to index an out-of-range subscript that accesses A[1].
//
// Scalar replacing *just* the outer index of the array is probably not
// going to be a win anyway, so just give up.
for (++I; I != E && (isa<ArrayType>(*I) || isa<PackedType>(*I)); ++I) {
uint64_t NumElements;
if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*I))
NumElements = SubArrayTy->getNumElements();
else
NumElements = cast<PackedType>(*I)->getNumElements();
if (!isa<ConstantInt>(I.getOperand())) return 0;
if (cast<ConstantInt>(I.getOperand())->getZExtValue() >= NumElements)
return 0;
}
} else {
// If this is an array index and the index is not constant, we cannot
// promote... that is unless the array has exactly one or two elements in
// it, in which case we CAN promote it, but we have to canonicalize this
// out if this is the only problem.
if ((NumElements == 1 || NumElements == 2) &&
AllUsersAreLoads(GEPI))
return 1; // Canonicalization required!
return 0;
}
}
// If there are any non-simple uses of this getelementptr, make sure to reject
// them.
return isSafeElementUse(GEPI);
}
/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
/// an aggregate can be broken down into elements. Return 0 if not, 3 if safe,
/// or 1 if safe after canonicalization has been performed.
///
int SROA::isSafeAllocaToScalarRepl(AllocationInst *AI) {
// Loop over the use list of the alloca. We can only transform it if all of
// the users are safe to transform.
//
int isSafe = 3;
for (Value::use_iterator I = AI->use_begin(), E = AI->use_end();
I != E; ++I) {
isSafe &= isSafeUseOfAllocation(cast<Instruction>(*I));
if (isSafe == 0) {
DOUT << "Cannot transform: " << *AI << " due to user: " << **I;
return 0;
}
}
// If we require cleanup, isSafe is now 1, otherwise it is 3.
return isSafe;
}
/// CanonicalizeAllocaUsers - If SROA reported that it can promote the specified
/// allocation, but only if cleaned up, perform the cleanups required.
void SROA::CanonicalizeAllocaUsers(AllocationInst *AI) {
// At this point, we know that the end result will be SROA'd and promoted, so
// we can insert ugly code if required so long as sroa+mem2reg will clean it
// up.
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ) {
GetElementPtrInst *GEPI = cast<GetElementPtrInst>(*UI++);
gep_type_iterator I = gep_type_begin(GEPI);
++I;
if (const ArrayType *AT = dyn_cast<ArrayType>(*I)) {
uint64_t NumElements = AT->getNumElements();
if (!isa<ConstantInt>(I.getOperand())) {
if (NumElements == 1) {
GEPI->setOperand(2, Constant::getNullValue(Type::Int32Ty));
} else {
assert(NumElements == 2 && "Unhandled case!");
// All users of the GEP must be loads. At each use of the GEP, insert
// two loads of the appropriate indexed GEP and select between them.
Value *IsOne = new ICmpInst(ICmpInst::ICMP_NE, I.getOperand(),
Constant::getNullValue(I.getOperand()->getType()),
"isone", GEPI);
// Insert the new GEP instructions, which are properly indexed.
std::vector<Value*> Indices(GEPI->op_begin()+1, GEPI->op_end());
Indices[1] = Constant::getNullValue(Type::Int32Ty);
Value *ZeroIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices,
GEPI->getName()+".0", GEPI);
Indices[1] = ConstantInt::get(Type::Int32Ty, 1);
Value *OneIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices,
GEPI->getName()+".1", GEPI);
// Replace all loads of the variable index GEP with loads from both
// indexes and a select.
while (!GEPI->use_empty()) {
LoadInst *LI = cast<LoadInst>(GEPI->use_back());
Value *Zero = new LoadInst(ZeroIdx, LI->getName()+".0", LI);
Value *One = new LoadInst(OneIdx , LI->getName()+".1", LI);
Value *R = new SelectInst(IsOne, One, Zero, LI->getName(), LI);
LI->replaceAllUsesWith(R);
LI->eraseFromParent();
}
GEPI->eraseFromParent();
}
}
}
}
}
/// MergeInType - Add the 'In' type to the accumulated type so far. If the
/// types are incompatible, return true, otherwise update Accum and return
/// false.
///
/// There are three cases we handle here:
/// 1) An effectively-integer union, where the pieces are stored into as
/// smaller integers (common with byte swap and other idioms).
/// 2) A union of vector types of the same size and potentially its elements.
/// Here we turn element accesses into insert/extract element operations.
/// 3) A union of scalar types, such as int/float or int/pointer. Here we
/// merge together into integers, allowing the xform to work with #1 as
/// well.
static bool MergeInType(const Type *In, const Type *&Accum,
const TargetData &TD) {
// If this is our first type, just use it.
const PackedType *PTy;
if (Accum == Type::VoidTy || In == Accum) {
Accum = In;
} else if (In == Type::VoidTy) {
// Noop.
} else if (In->isInteger() && Accum->isInteger()) { // integer union.
// Otherwise pick whichever type is larger.
if (cast<IntegerType>(In)->getBitWidth() >
cast<IntegerType>(Accum)->getBitWidth())
Accum = In;
} else if (isa<PointerType>(In) && isa<PointerType>(Accum)) {
// Pointer unions just stay as one of the pointers.
} else if (isa<PackedType>(In) || isa<PackedType>(Accum)) {
if ((PTy = dyn_cast<PackedType>(Accum)) &&
PTy->getElementType() == In) {
// Accum is a vector, and we are accessing an element: ok.
} else if ((PTy = dyn_cast<PackedType>(In)) &&
PTy->getElementType() == Accum) {
// In is a vector, and accum is an element: ok, remember In.
Accum = In;
} else if ((PTy = dyn_cast<PackedType>(In)) && isa<PackedType>(Accum) &&
PTy->getBitWidth() == cast<PackedType>(Accum)->getBitWidth()) {
// Two vectors of the same size: keep Accum.
} else {
// Cannot insert an short into a <4 x int> or handle
// <2 x int> -> <4 x int>
return true;
}
} else {
// Pointer/FP/Integer unions merge together as integers.
switch (Accum->getTypeID()) {
case Type::PointerTyID: Accum = TD.getIntPtrType(); break;
case Type::FloatTyID: Accum = Type::Int32Ty; break;
case Type::DoubleTyID: Accum = Type::Int64Ty; break;
default:
assert(Accum->isInteger() && "Unknown FP type!");
break;
}
switch (In->getTypeID()) {
case Type::PointerTyID: In = TD.getIntPtrType(); break;
case Type::FloatTyID: In = Type::Int32Ty; break;
case Type::DoubleTyID: In = Type::Int64Ty; break;
default:
assert(In->isInteger() && "Unknown FP type!");
break;
}
return MergeInType(In, Accum, TD);
}
return false;
}
/// getUIntAtLeastAsBitAs - Return an unsigned integer type that is at least
/// as big as the specified type. If there is no suitable type, this returns
/// null.
const Type *getUIntAtLeastAsBitAs(unsigned NumBits) {
if (NumBits > 64) return 0;
if (NumBits > 32) return Type::Int64Ty;
if (NumBits > 16) return Type::Int32Ty;
if (NumBits > 8) return Type::Int16Ty;
return Type::Int8Ty;
}
/// CanConvertToScalar - V is a pointer. If we can convert the pointee to a
/// single scalar integer type, return that type. Further, if the use is not
/// a completely trivial use that mem2reg could promote, set IsNotTrivial. If
/// there are no uses of this pointer, return Type::VoidTy to differentiate from
/// failure.
///
const Type *SROA::CanConvertToScalar(Value *V, bool &IsNotTrivial) {
const Type *UsedType = Type::VoidTy; // No uses, no forced type.
const TargetData &TD = getAnalysis<TargetData>();
const PointerType *PTy = cast<PointerType>(V->getType());
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
if (MergeInType(LI->getType(), UsedType, TD))
return 0;
} else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
// Storing the pointer, not into the value?
if (SI->getOperand(0) == V) return 0;
// NOTE: We could handle storing of FP imms into integers here!
if (MergeInType(SI->getOperand(0)->getType(), UsedType, TD))
return 0;
} else if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
IsNotTrivial = true;
const Type *SubTy = CanConvertToScalar(CI, IsNotTrivial);
if (!SubTy || MergeInType(SubTy, UsedType, TD)) return 0;
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
// Check to see if this is stepping over an element: GEP Ptr, int C
if (GEP->getNumOperands() == 2 && isa<ConstantInt>(GEP->getOperand(1))) {
unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue();
unsigned ElSize = TD.getTypeSize(PTy->getElementType());
unsigned BitOffset = Idx*ElSize*8;
if (BitOffset > 64 || !isPowerOf2_32(ElSize)) return 0;
IsNotTrivial = true;
const Type *SubElt = CanConvertToScalar(GEP, IsNotTrivial);
if (SubElt == 0) return 0;
if (SubElt != Type::VoidTy && SubElt->isInteger()) {
const Type *NewTy =
getUIntAtLeastAsBitAs(TD.getTypeSize(SubElt)*8+BitOffset);
if (NewTy == 0 || MergeInType(NewTy, UsedType, TD)) return 0;
continue;
}
} else if (GEP->getNumOperands() == 3 &&
isa<ConstantInt>(GEP->getOperand(1)) &&
isa<ConstantInt>(GEP->getOperand(2)) &&
cast<Constant>(GEP->getOperand(1))->isNullValue()) {
// We are stepping into an element, e.g. a structure or an array:
// GEP Ptr, int 0, uint C
const Type *AggTy = PTy->getElementType();
unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
if (const ArrayType *ATy = dyn_cast<ArrayType>(AggTy)) {
if (Idx >= ATy->getNumElements()) return 0; // Out of range.
} else if (const PackedType *PackedTy = dyn_cast<PackedType>(AggTy)) {
// Getting an element of the packed vector.
if (Idx >= PackedTy->getNumElements()) return 0; // Out of range.
// Merge in the packed type.
if (MergeInType(PackedTy, UsedType, TD)) return 0;
const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial);
if (SubTy == 0) return 0;
if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD))
return 0;
// We'll need to change this to an insert/extract element operation.
IsNotTrivial = true;
continue; // Everything looks ok
} else if (isa<StructType>(AggTy)) {
// Structs are always ok.
} else {
return 0;
}
const Type *NTy = getUIntAtLeastAsBitAs(TD.getTypeSize(AggTy)*8);
if (NTy == 0 || MergeInType(NTy, UsedType, TD)) return 0;
const Type *SubTy = CanConvertToScalar(GEP, IsNotTrivial);
if (SubTy == 0) return 0;
if (SubTy != Type::VoidTy && MergeInType(SubTy, UsedType, TD))
return 0;
continue; // Everything looks ok
}
return 0;
} else {
// Cannot handle this!
return 0;
}
}
return UsedType;
}
/// ConvertToScalar - The specified alloca passes the CanConvertToScalar
/// predicate and is non-trivial. Convert it to something that can be trivially
/// promoted into a register by mem2reg.
void SROA::ConvertToScalar(AllocationInst *AI, const Type *ActualTy) {
DOUT << "CONVERT TO SCALAR: " << *AI << " TYPE = "
<< *ActualTy << "\n";
++NumConverted;
BasicBlock *EntryBlock = AI->getParent();
assert(EntryBlock == &EntryBlock->getParent()->front() &&
"Not in the entry block!");
EntryBlock->getInstList().remove(AI); // Take the alloca out of the program.
// Create and insert the alloca.
AllocaInst *NewAI = new AllocaInst(ActualTy, 0, AI->getName(),
EntryBlock->begin());
ConvertUsesToScalar(AI, NewAI, 0);
delete AI;
}
/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
/// directly. This happens when we are converting an "integer union" to a
/// single integer scalar, or when we are converting a "vector union" to a
/// vector with insert/extractelement instructions.
///
/// Offset is an offset from the original alloca, in bits that need to be
/// shifted to the right. By the end of this, there should be no uses of Ptr.
void SROA::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, unsigned Offset) {
bool isVectorInsert = isa<PackedType>(NewAI->getType()->getElementType());
const TargetData &TD = getAnalysis<TargetData>();
while (!Ptr->use_empty()) {
Instruction *User = cast<Instruction>(Ptr->use_back());
if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
// The load is a bit extract from NewAI shifted right by Offset bits.
Value *NV = new LoadInst(NewAI, LI->getName(), LI);
if (NV->getType() != LI->getType()) {
if (const PackedType *PTy = dyn_cast<PackedType>(NV->getType())) {
// If the result alloca is a packed type, this is either an element
// access or a bitcast to another packed type.
if (isa<PackedType>(LI->getType())) {
NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI);
} else {
// Must be an element access.
unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8);
NV = new ExtractElementInst(
NV, ConstantInt::get(Type::Int32Ty, Elt), "tmp", LI);
}
} else if (isa<PointerType>(NV->getType())) {
assert(isa<PointerType>(LI->getType()));
// Must be ptr->ptr cast. Anything else would result in NV being
// an integer.
NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI);
} else {
assert(NV->getType()->isInteger() && "Unknown promotion!");
if (Offset && Offset < TD.getTypeSize(NV->getType())*8) {
NV = new ShiftInst(Instruction::LShr, NV,
ConstantInt::get(Type::Int8Ty, Offset),
LI->getName(), LI);
}
// If the result is an integer, this is a trunc or bitcast.
if (LI->getType()->isInteger()) {
NV = CastInst::createTruncOrBitCast(NV, LI->getType(),
LI->getName(), LI);
} else if (LI->getType()->isFloatingPoint()) {
// If needed, truncate the integer to the appropriate size.
if (NV->getType()->getPrimitiveSizeInBits() >
LI->getType()->getPrimitiveSizeInBits()) {
switch (LI->getType()->getTypeID()) {
default: assert(0 && "Unknown FP type!");
case Type::FloatTyID:
NV = new TruncInst(NV, Type::Int32Ty, LI->getName(), LI);
break;
case Type::DoubleTyID:
NV = new TruncInst(NV, Type::Int64Ty, LI->getName(), LI);
break;
}
}
// Then do a bitcast.
NV = new BitCastInst(NV, LI->getType(), LI->getName(), LI);
} else {
// Otherwise must be a pointer.
NV = new IntToPtrInst(NV, LI->getType(), LI->getName(), LI);
}
}
}
LI->replaceAllUsesWith(NV);
LI->eraseFromParent();
} else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
assert(SI->getOperand(0) != Ptr && "Consistency error!");
// Convert the stored type to the actual type, shift it left to insert
// then 'or' into place.
Value *SV = SI->getOperand(0);
const Type *AllocaType = NewAI->getType()->getElementType();
if (SV->getType() != AllocaType) {
Value *Old = new LoadInst(NewAI, NewAI->getName()+".in", SI);
if (const PackedType *PTy = dyn_cast<PackedType>(AllocaType)) {
// If the result alloca is a packed type, this is either an element
// access or a bitcast to another packed type.
if (isa<PackedType>(SV->getType())) {
SV = new BitCastInst(SV, AllocaType, SV->getName(), SI);
} else {
// Must be an element insertion.
unsigned Elt = Offset/(TD.getTypeSize(PTy->getElementType())*8);
SV = new InsertElementInst(Old, SV,
ConstantInt::get(Type::Int32Ty, Elt),
"tmp", SI);
}
} else {
// If SV is a float, convert it to the appropriate integer type.
// If it is a pointer, do the same, and also handle ptr->ptr casts
// here.
switch (SV->getType()->getTypeID()) {
default:
assert(!SV->getType()->isFloatingPoint() && "Unknown FP type!");
break;
case Type::FloatTyID:
SV = new BitCastInst(SV, Type::Int32Ty, SV->getName(), SI);
break;
case Type::DoubleTyID:
SV = new BitCastInst(SV, Type::Int64Ty, SV->getName(), SI);
break;
case Type::PointerTyID:
if (isa<PointerType>(AllocaType))
SV = new BitCastInst(SV, AllocaType, SV->getName(), SI);
else
SV = new PtrToIntInst(SV, TD.getIntPtrType(), SV->getName(), SI);
break;
}
unsigned SrcSize = TD.getTypeSize(SV->getType())*8;
// Always zero extend the value if needed.
if (SV->getType() != AllocaType)
SV = CastInst::createZExtOrBitCast(SV, AllocaType,
SV->getName(), SI);
if (Offset && Offset < AllocaType->getPrimitiveSizeInBits())
SV = new ShiftInst(Instruction::Shl, SV,
ConstantInt::get(Type::Int8Ty, Offset),
SV->getName()+".adj", SI);
// Mask out the bits we are about to insert from the old value.
unsigned TotalBits = TD.getTypeSize(SV->getType())*8;
if (TotalBits != SrcSize) {
assert(TotalBits > SrcSize);
uint64_t Mask = ~(((1ULL << SrcSize)-1) << Offset);
Mask = Mask & cast<IntegerType>(SV->getType())->getBitMask();
Old = BinaryOperator::createAnd(Old,
ConstantInt::get(Old->getType(), Mask),
Old->getName()+".mask", SI);
SV = BinaryOperator::createOr(Old, SV, SV->getName()+".ins", SI);
}
}
}
new StoreInst(SV, NewAI, SI);
SI->eraseFromParent();
} else if (CastInst *CI = dyn_cast<CastInst>(User)) {
unsigned NewOff = Offset;
const TargetData &TD = getAnalysis<TargetData>();
if (TD.isBigEndian() && !isVectorInsert) {
// Adjust the pointer. For example, storing 16-bits into a 32-bit
// alloca with just a cast makes it modify the top 16-bits.
const Type *SrcTy = cast<PointerType>(Ptr->getType())->getElementType();
const Type *DstTy = cast<PointerType>(CI->getType())->getElementType();
int PtrDiffBits = TD.getTypeSize(SrcTy)*8-TD.getTypeSize(DstTy)*8;
NewOff += PtrDiffBits;
}
ConvertUsesToScalar(CI, NewAI, NewOff);
CI->eraseFromParent();
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
const PointerType *AggPtrTy =
cast<PointerType>(GEP->getOperand(0)->getType());
const TargetData &TD = getAnalysis<TargetData>();
unsigned AggSizeInBits = TD.getTypeSize(AggPtrTy->getElementType())*8;
// Check to see if this is stepping over an element: GEP Ptr, int C
unsigned NewOffset = Offset;
if (GEP->getNumOperands() == 2) {
unsigned Idx = cast<ConstantInt>(GEP->getOperand(1))->getZExtValue();
unsigned BitOffset = Idx*AggSizeInBits;
if (TD.isLittleEndian() || isVectorInsert)
NewOffset += BitOffset;
else
NewOffset -= BitOffset;
} else if (GEP->getNumOperands() == 3) {
// We know that operand #2 is zero.
unsigned Idx = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
const Type *AggTy = AggPtrTy->getElementType();
if (const SequentialType *SeqTy = dyn_cast<SequentialType>(AggTy)) {
unsigned ElSizeBits = TD.getTypeSize(SeqTy->getElementType())*8;
if (TD.isLittleEndian() || isVectorInsert)
NewOffset += ElSizeBits*Idx;
else
NewOffset += AggSizeInBits-ElSizeBits*(Idx+1);
} else if (const StructType *STy = dyn_cast<StructType>(AggTy)) {
unsigned EltBitOffset = TD.getStructLayout(STy)->MemberOffsets[Idx]*8;
if (TD.isLittleEndian() || isVectorInsert)
NewOffset += EltBitOffset;
else {
const PointerType *ElPtrTy = cast<PointerType>(GEP->getType());
unsigned ElSizeBits = TD.getTypeSize(ElPtrTy->getElementType())*8;
NewOffset += AggSizeInBits-(EltBitOffset+ElSizeBits);
}
} else {
assert(0 && "Unsupported operation!");
abort();
}
} else {
assert(0 && "Unsupported operation!");
abort();
}
ConvertUsesToScalar(GEP, NewAI, NewOffset);
GEP->eraseFromParent();
} else {
assert(0 && "Unsupported operation!");
abort();
}
}
}
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