mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-21 03:29:40 +00:00
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19379 91177308-0d34-0410-b5e6-96231b3b80d8
380 lines
14 KiB
C++
380 lines
14 KiB
C++
//===- 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.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#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/Support/GetElementPtrTypeIterator.h"
|
|
#include "llvm/Target/TargetData.h"
|
|
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/ADT/StringExtras.h"
|
|
using namespace llvm;
|
|
|
|
namespace {
|
|
Statistic<> NumReplaced("scalarrepl", "Number of allocas broken up");
|
|
Statistic<> NumPromoted("scalarrepl", "Number of allocas promoted");
|
|
|
|
struct 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);
|
|
};
|
|
|
|
RegisterOpt<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();
|
|
|
|
// 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;
|
|
}
|
|
|
|
DEBUG(std::cerr << "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->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->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))->getRawValue();
|
|
|
|
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::IntTy));
|
|
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->getParent()->getInstList().erase(AI);
|
|
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:
|
|
DEBUG(std::cerr << " 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 safe to transform if it is 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 (ConstantInt *CI = dyn_cast<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))->getRawValue() >= 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)
|
|
return AllUsersAreLoads(GEPI) ? 1 : 0; // 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) {
|
|
DEBUG(std::cerr << "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::IntTy));
|
|
} 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 = BinaryOperator::createSetNE(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::IntTy);
|
|
Value *ZeroIdx = new GetElementPtrInst(GEPI->getOperand(0), Indices,
|
|
GEPI->getName()+".0", GEPI);
|
|
Indices[1] = ConstantInt::get(Type::IntTy, 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();
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|