//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "gvn"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/GlobalVariable.h"
-#include "llvm/IRBuilder.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Metadata.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Hashing.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Analysis/PHITransAddr.h"
#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/Assembly/Writer.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
-#include "llvm/Support/PatternMatch.h"
-#include "llvm/DataLayout.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
+#include <vector>
using namespace llvm;
using namespace PatternMatch;
+#define DEBUG_TYPE "gvn"
+
STATISTIC(NumGVNInstr, "Number of instructions deleted");
STATISTIC(NumGVNLoad, "Number of loads deleted");
STATISTIC(NumGVNPRE, "Number of instructions PRE'd");
}
Expression ValueTable::create_extractvalue_expression(ExtractValueInst *EI) {
- assert(EI != 0 && "Not an ExtractValueInst?");
+ assert(EI && "Not an ExtractValueInst?");
Expression e;
e.type = EI->getType();
e.opcode = 0;
IntrinsicInst *I = dyn_cast<IntrinsicInst>(EI->getAggregateOperand());
- if (I != 0 && EI->getNumIndices() == 1 && *EI->idx_begin() == 0 ) {
+ if (I != nullptr && EI->getNumIndices() == 1 && *EI->idx_begin() == 0 ) {
// EI might be an extract from one of our recognised intrinsics. If it
// is we'll synthesize a semantically equivalent expression instead on
// an extract value expression.
const MemoryDependenceAnalysis::NonLocalDepInfo &deps =
MD->getNonLocalCallDependency(CallSite(C));
// FIXME: Move the checking logic to MemDep!
- CallInst* cdep = 0;
+ CallInst* cdep = nullptr;
// Check to see if we have a single dominating call instruction that is
// identical to C.
// We don't handle non-definitions. If we already have a call, reject
// instruction dependencies.
- if (!I->getResult().isDef() || cdep != 0) {
- cdep = 0;
+ if (!I->getResult().isDef() || cdep != nullptr) {
+ cdep = nullptr;
break;
}
continue;
}
- cdep = 0;
+ cdep = nullptr;
break;
}
//===----------------------------------------------------------------------===//
namespace {
+ class GVN;
+ struct AvailableValueInBlock {
+ /// BB - The basic block in question.
+ BasicBlock *BB;
+ enum ValType {
+ SimpleVal, // A simple offsetted value that is accessed.
+ LoadVal, // A value produced by a load.
+ MemIntrin, // A memory intrinsic which is loaded from.
+ UndefVal // A UndefValue representing a value from dead block (which
+ // is not yet physically removed from the CFG).
+ };
+
+ /// V - The value that is live out of the block.
+ PointerIntPair<Value *, 2, ValType> Val;
+
+ /// Offset - The byte offset in Val that is interesting for the load query.
+ unsigned Offset;
+
+ static AvailableValueInBlock get(BasicBlock *BB, Value *V,
+ unsigned Offset = 0) {
+ AvailableValueInBlock Res;
+ Res.BB = BB;
+ Res.Val.setPointer(V);
+ Res.Val.setInt(SimpleVal);
+ Res.Offset = Offset;
+ return Res;
+ }
+
+ static AvailableValueInBlock getMI(BasicBlock *BB, MemIntrinsic *MI,
+ unsigned Offset = 0) {
+ AvailableValueInBlock Res;
+ Res.BB = BB;
+ Res.Val.setPointer(MI);
+ Res.Val.setInt(MemIntrin);
+ Res.Offset = Offset;
+ return Res;
+ }
+
+ static AvailableValueInBlock getLoad(BasicBlock *BB, LoadInst *LI,
+ unsigned Offset = 0) {
+ AvailableValueInBlock Res;
+ Res.BB = BB;
+ Res.Val.setPointer(LI);
+ Res.Val.setInt(LoadVal);
+ Res.Offset = Offset;
+ return Res;
+ }
+
+ static AvailableValueInBlock getUndef(BasicBlock *BB) {
+ AvailableValueInBlock Res;
+ Res.BB = BB;
+ Res.Val.setPointer(nullptr);
+ Res.Val.setInt(UndefVal);
+ Res.Offset = 0;
+ return Res;
+ }
+
+ bool isSimpleValue() const { return Val.getInt() == SimpleVal; }
+ bool isCoercedLoadValue() const { return Val.getInt() == LoadVal; }
+ bool isMemIntrinValue() const { return Val.getInt() == MemIntrin; }
+ bool isUndefValue() const { return Val.getInt() == UndefVal; }
+
+ Value *getSimpleValue() const {
+ assert(isSimpleValue() && "Wrong accessor");
+ return Val.getPointer();
+ }
+
+ LoadInst *getCoercedLoadValue() const {
+ assert(isCoercedLoadValue() && "Wrong accessor");
+ return cast<LoadInst>(Val.getPointer());
+ }
+
+ MemIntrinsic *getMemIntrinValue() const {
+ assert(isMemIntrinValue() && "Wrong accessor");
+ return cast<MemIntrinsic>(Val.getPointer());
+ }
+
+ /// MaterializeAdjustedValue - Emit code into this block to adjust the value
+ /// defined here to the specified type. This handles various coercion cases.
+ Value *MaterializeAdjustedValue(Type *LoadTy, GVN &gvn) const;
+ };
class GVN : public FunctionPass {
bool NoLoads;
MemoryDependenceAnalysis *MD;
DominatorTree *DT;
- const DataLayout *TD;
+ const DataLayout *DL;
const TargetLibraryInfo *TLI;
+ SetVector<BasicBlock *> DeadBlocks;
ValueTable VN;
BumpPtrAllocator TableAllocator;
SmallVector<Instruction*, 8> InstrsToErase;
+
+ typedef SmallVector<NonLocalDepResult, 64> LoadDepVect;
+ typedef SmallVector<AvailableValueInBlock, 64> AvailValInBlkVect;
+ typedef SmallVector<BasicBlock*, 64> UnavailBlkVect;
+
public:
static char ID; // Pass identification, replacement for typeid
explicit GVN(bool noloads = false)
- : FunctionPass(ID), NoLoads(noloads), MD(0) {
+ : FunctionPass(ID), NoLoads(noloads), MD(nullptr) {
initializeGVNPass(*PassRegistry::getPassRegistry());
}
- bool runOnFunction(Function &F);
+ bool runOnFunction(Function &F) override;
/// markInstructionForDeletion - This removes the specified instruction from
/// our various maps and marks it for deletion.
InstrsToErase.push_back(I);
}
- const DataLayout *getDataLayout() const { return TD; }
+ const DataLayout *getDataLayout() const { return DL; }
DominatorTree &getDominatorTree() const { return *DT; }
AliasAnalysis *getAliasAnalysis() const { return VN.getAliasAnalysis(); }
MemoryDependenceAnalysis &getMemDep() const { return *MD; }
/// removeFromLeaderTable - Scan the list of values corresponding to a given
/// value number, and remove the given instruction if encountered.
void removeFromLeaderTable(uint32_t N, Instruction *I, BasicBlock *BB) {
- LeaderTableEntry* Prev = 0;
+ LeaderTableEntry* Prev = nullptr;
LeaderTableEntry* Curr = &LeaderTable[N];
while (Curr->Val != I || Curr->BB != BB) {
Prev->Next = Curr->Next;
} else {
if (!Curr->Next) {
- Curr->Val = 0;
- Curr->BB = 0;
+ Curr->Val = nullptr;
+ Curr->BB = nullptr;
} else {
LeaderTableEntry* Next = Curr->Next;
Curr->Val = Next->Val;
SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit;
// This transformation requires dominator postdominator info
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<DominatorTree>();
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<TargetLibraryInfo>();
if (!NoLoads)
AU.addRequired<MemoryDependenceAnalysis>();
AU.addRequired<AliasAnalysis>();
- AU.addPreserved<DominatorTree>();
+ AU.addPreserved<DominatorTreeWrapperPass>();
AU.addPreserved<AliasAnalysis>();
}
- // Helper fuctions
- // FIXME: eliminate or document these better
+ // Helper fuctions of redundant load elimination
bool processLoad(LoadInst *L);
- bool processInstruction(Instruction *I);
bool processNonLocalLoad(LoadInst *L);
+ void AnalyzeLoadAvailability(LoadInst *LI, LoadDepVect &Deps,
+ AvailValInBlkVect &ValuesPerBlock,
+ UnavailBlkVect &UnavailableBlocks);
+ bool PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
+ UnavailBlkVect &UnavailableBlocks);
+
+ // Other helper routines
+ bool processInstruction(Instruction *I);
bool processBlock(BasicBlock *BB);
void dump(DenseMap<uint32_t, Value*> &d);
bool iterateOnFunction(Function &F);
void cleanupGlobalSets();
void verifyRemoved(const Instruction *I) const;
bool splitCriticalEdges();
+ BasicBlock *splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ);
unsigned replaceAllDominatedUsesWith(Value *From, Value *To,
const BasicBlockEdge &Root);
bool propagateEquality(Value *LHS, Value *RHS, const BasicBlockEdge &Root);
+ bool processFoldableCondBr(BranchInst *BI);
+ void addDeadBlock(BasicBlock *BB);
+ void assignValNumForDeadCode();
};
char GVN::ID = 0;
INITIALIZE_PASS_BEGIN(GVN, "gvn", "Global Value Numbering", false, false)
INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
-INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(GVN, "gvn", "Global Value Numbering", false, false)
// Mark as unavailable.
EntryVal = 0;
- for (succ_iterator I = succ_begin(Entry), E = succ_end(Entry); I != E; ++I)
- BBWorklist.push_back(*I);
+ BBWorklist.append(succ_begin(Entry), succ_end(Entry));
} while (!BBWorklist.empty());
return false;
/// CoerceAvailableValueToLoadType will succeed.
static bool CanCoerceMustAliasedValueToLoad(Value *StoredVal,
Type *LoadTy,
- const DataLayout &TD) {
+ const DataLayout &DL) {
// If the loaded or stored value is an first class array or struct, don't try
// to transform them. We need to be able to bitcast to integer.
if (LoadTy->isStructTy() || LoadTy->isArrayTy() ||
return false;
// The store has to be at least as big as the load.
- if (TD.getTypeSizeInBits(StoredVal->getType()) <
- TD.getTypeSizeInBits(LoadTy))
+ if (DL.getTypeSizeInBits(StoredVal->getType()) <
+ DL.getTypeSizeInBits(LoadTy))
return false;
return true;
}
-
/// CoerceAvailableValueToLoadType - If we saw a store of a value to memory, and
/// then a load from a must-aliased pointer of a different type, try to coerce
/// the stored value. LoadedTy is the type of the load we want to replace and
static Value *CoerceAvailableValueToLoadType(Value *StoredVal,
Type *LoadedTy,
Instruction *InsertPt,
- const DataLayout &TD) {
- if (!CanCoerceMustAliasedValueToLoad(StoredVal, LoadedTy, TD))
- return 0;
+ const DataLayout &DL) {
+ if (!CanCoerceMustAliasedValueToLoad(StoredVal, LoadedTy, DL))
+ return nullptr;
// If this is already the right type, just return it.
Type *StoredValTy = StoredVal->getType();
- uint64_t StoreSize = TD.getTypeSizeInBits(StoredValTy);
- uint64_t LoadSize = TD.getTypeSizeInBits(LoadedTy);
+ uint64_t StoreSize = DL.getTypeSizeInBits(StoredValTy);
+ uint64_t LoadSize = DL.getTypeSizeInBits(LoadedTy);
// If the store and reload are the same size, we can always reuse it.
if (StoreSize == LoadSize) {
// Pointer to Pointer -> use bitcast.
- if (StoredValTy->isPointerTy() && LoadedTy->isPointerTy())
+ if (StoredValTy->getScalarType()->isPointerTy() &&
+ LoadedTy->getScalarType()->isPointerTy())
return new BitCastInst(StoredVal, LoadedTy, "", InsertPt);
// Convert source pointers to integers, which can be bitcast.
- if (StoredValTy->isPointerTy()) {
- StoredValTy = TD.getIntPtrType(StoredValTy->getContext());
+ if (StoredValTy->getScalarType()->isPointerTy()) {
+ StoredValTy = DL.getIntPtrType(StoredValTy);
StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
}
Type *TypeToCastTo = LoadedTy;
- if (TypeToCastTo->isPointerTy())
- TypeToCastTo = TD.getIntPtrType(StoredValTy->getContext());
+ if (TypeToCastTo->getScalarType()->isPointerTy())
+ TypeToCastTo = DL.getIntPtrType(TypeToCastTo);
if (StoredValTy != TypeToCastTo)
StoredVal = new BitCastInst(StoredVal, TypeToCastTo, "", InsertPt);
// Cast to pointer if the load needs a pointer type.
- if (LoadedTy->isPointerTy())
+ if (LoadedTy->getScalarType()->isPointerTy())
StoredVal = new IntToPtrInst(StoredVal, LoadedTy, "", InsertPt);
return StoredVal;
assert(StoreSize >= LoadSize && "CanCoerceMustAliasedValueToLoad fail");
// Convert source pointers to integers, which can be manipulated.
- if (StoredValTy->isPointerTy()) {
- StoredValTy = TD.getIntPtrType(StoredValTy->getContext());
+ if (StoredValTy->getScalarType()->isPointerTy()) {
+ StoredValTy = DL.getIntPtrType(StoredValTy);
StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
}
// If this is a big-endian system, we need to shift the value down to the low
// bits so that a truncate will work.
- if (TD.isBigEndian()) {
+ if (DL.isBigEndian()) {
Constant *Val = ConstantInt::get(StoredVal->getType(), StoreSize-LoadSize);
StoredVal = BinaryOperator::CreateLShr(StoredVal, Val, "tmp", InsertPt);
}
return StoredVal;
// If the result is a pointer, inttoptr.
- if (LoadedTy->isPointerTy())
+ if (LoadedTy->getScalarType()->isPointerTy())
return new IntToPtrInst(StoredVal, LoadedTy, "inttoptr", InsertPt);
// Otherwise, bitcast.
static int AnalyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr,
Value *WritePtr,
uint64_t WriteSizeInBits,
- const DataLayout &TD) {
+ const DataLayout &DL) {
// If the loaded or stored value is a first class array or struct, don't try
// to transform them. We need to be able to bitcast to integer.
if (LoadTy->isStructTy() || LoadTy->isArrayTy())
return -1;
int64_t StoreOffset = 0, LoadOffset = 0;
- Value *StoreBase = GetPointerBaseWithConstantOffset(WritePtr, StoreOffset,TD);
- Value *LoadBase = GetPointerBaseWithConstantOffset(LoadPtr, LoadOffset, TD);
+ Value *StoreBase = GetPointerBaseWithConstantOffset(WritePtr,StoreOffset,&DL);
+ Value *LoadBase = GetPointerBaseWithConstantOffset(LoadPtr, LoadOffset, &DL);
if (StoreBase != LoadBase)
return -1;
// If the load and store don't overlap at all, the store doesn't provide
// anything to the load. In this case, they really don't alias at all, AA
// must have gotten confused.
- uint64_t LoadSize = TD.getTypeSizeInBits(LoadTy);
+ uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy);
if ((WriteSizeInBits & 7) | (LoadSize & 7))
return -1;
/// memdep query of a load that ends up being a clobbering store.
static int AnalyzeLoadFromClobberingStore(Type *LoadTy, Value *LoadPtr,
StoreInst *DepSI,
- const DataLayout &TD) {
+ const DataLayout &DL) {
// Cannot handle reading from store of first-class aggregate yet.
if (DepSI->getValueOperand()->getType()->isStructTy() ||
DepSI->getValueOperand()->getType()->isArrayTy())
return -1;
Value *StorePtr = DepSI->getPointerOperand();
- uint64_t StoreSize =TD.getTypeSizeInBits(DepSI->getValueOperand()->getType());
+ uint64_t StoreSize =DL.getTypeSizeInBits(DepSI->getValueOperand()->getType());
return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr,
- StorePtr, StoreSize, TD);
+ StorePtr, StoreSize, DL);
}
/// AnalyzeLoadFromClobberingLoad - This function is called when we have a
/// memdep query of a load that ends up being clobbered by another load. See if
/// the other load can feed into the second load.
static int AnalyzeLoadFromClobberingLoad(Type *LoadTy, Value *LoadPtr,
- LoadInst *DepLI, const DataLayout &TD){
+ LoadInst *DepLI, const DataLayout &DL){
// Cannot handle reading from store of first-class aggregate yet.
if (DepLI->getType()->isStructTy() || DepLI->getType()->isArrayTy())
return -1;
Value *DepPtr = DepLI->getPointerOperand();
- uint64_t DepSize = TD.getTypeSizeInBits(DepLI->getType());
- int R = AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, DepSize, TD);
+ uint64_t DepSize = DL.getTypeSizeInBits(DepLI->getType());
+ int R = AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, DepSize, DL);
if (R != -1) return R;
// If we have a load/load clobber an DepLI can be widened to cover this load,
// then we should widen it!
int64_t LoadOffs = 0;
const Value *LoadBase =
- GetPointerBaseWithConstantOffset(LoadPtr, LoadOffs, TD);
- unsigned LoadSize = TD.getTypeStoreSize(LoadTy);
+ GetPointerBaseWithConstantOffset(LoadPtr, LoadOffs, &DL);
+ unsigned LoadSize = DL.getTypeStoreSize(LoadTy);
unsigned Size = MemoryDependenceAnalysis::
- getLoadLoadClobberFullWidthSize(LoadBase, LoadOffs, LoadSize, DepLI, TD);
+ getLoadLoadClobberFullWidthSize(LoadBase, LoadOffs, LoadSize, DepLI, DL);
if (Size == 0) return -1;
- return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, Size*8, TD);
+ return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, Size*8, DL);
}
static int AnalyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr,
MemIntrinsic *MI,
- const DataLayout &TD) {
+ const DataLayout &DL) {
// If the mem operation is a non-constant size, we can't handle it.
ConstantInt *SizeCst = dyn_cast<ConstantInt>(MI->getLength());
- if (SizeCst == 0) return -1;
+ if (!SizeCst) return -1;
uint64_t MemSizeInBits = SizeCst->getZExtValue()*8;
// If this is memset, we just need to see if the offset is valid in the size
// of the memset..
if (MI->getIntrinsicID() == Intrinsic::memset)
return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, MI->getDest(),
- MemSizeInBits, TD);
+ MemSizeInBits, DL);
// If we have a memcpy/memmove, the only case we can handle is if this is a
// copy from constant memory. In that case, we can read directly from the
MemTransferInst *MTI = cast<MemTransferInst>(MI);
Constant *Src = dyn_cast<Constant>(MTI->getSource());
- if (Src == 0) return -1;
+ if (!Src) return -1;
- GlobalVariable *GV = dyn_cast<GlobalVariable>(GetUnderlyingObject(Src, &TD));
- if (GV == 0 || !GV->isConstant()) return -1;
+ GlobalVariable *GV = dyn_cast<GlobalVariable>(GetUnderlyingObject(Src, &DL));
+ if (!GV || !GV->isConstant()) return -1;
// See if the access is within the bounds of the transfer.
int Offset = AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr,
- MI->getDest(), MemSizeInBits, TD);
+ MI->getDest(), MemSizeInBits, DL);
if (Offset == -1)
return Offset;
+ unsigned AS = Src->getType()->getPointerAddressSpace();
// Otherwise, see if we can constant fold a load from the constant with the
// offset applied as appropriate.
Src = ConstantExpr::getBitCast(Src,
- llvm::Type::getInt8PtrTy(Src->getContext()));
+ Type::getInt8PtrTy(Src->getContext(), AS));
Constant *OffsetCst =
ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
Src = ConstantExpr::getGetElementPtr(Src, OffsetCst);
- Src = ConstantExpr::getBitCast(Src, PointerType::getUnqual(LoadTy));
- if (ConstantFoldLoadFromConstPtr(Src, &TD))
+ Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
+ if (ConstantFoldLoadFromConstPtr(Src, &DL))
return Offset;
return -1;
}
/// before we give up.
static Value *GetStoreValueForLoad(Value *SrcVal, unsigned Offset,
Type *LoadTy,
- Instruction *InsertPt, const DataLayout &TD){
+ Instruction *InsertPt, const DataLayout &DL){
LLVMContext &Ctx = SrcVal->getType()->getContext();
- uint64_t StoreSize = (TD.getTypeSizeInBits(SrcVal->getType()) + 7) / 8;
- uint64_t LoadSize = (TD.getTypeSizeInBits(LoadTy) + 7) / 8;
+ uint64_t StoreSize = (DL.getTypeSizeInBits(SrcVal->getType()) + 7) / 8;
+ uint64_t LoadSize = (DL.getTypeSizeInBits(LoadTy) + 7) / 8;
IRBuilder<> Builder(InsertPt->getParent(), InsertPt);
// Compute which bits of the stored value are being used by the load. Convert
// to an integer type to start with.
- if (SrcVal->getType()->isPointerTy())
- SrcVal = Builder.CreatePtrToInt(SrcVal, TD.getIntPtrType(Ctx));
+ if (SrcVal->getType()->getScalarType()->isPointerTy())
+ SrcVal = Builder.CreatePtrToInt(SrcVal,
+ DL.getIntPtrType(SrcVal->getType()));
if (!SrcVal->getType()->isIntegerTy())
SrcVal = Builder.CreateBitCast(SrcVal, IntegerType::get(Ctx, StoreSize*8));
// Shift the bits to the least significant depending on endianness.
unsigned ShiftAmt;
- if (TD.isLittleEndian())
+ if (DL.isLittleEndian())
ShiftAmt = Offset*8;
else
ShiftAmt = (StoreSize-LoadSize-Offset)*8;
if (LoadSize != StoreSize)
SrcVal = Builder.CreateTrunc(SrcVal, IntegerType::get(Ctx, LoadSize*8));
- return CoerceAvailableValueToLoadType(SrcVal, LoadTy, InsertPt, TD);
+ return CoerceAvailableValueToLoadType(SrcVal, LoadTy, InsertPt, DL);
}
/// GetLoadValueForLoad - This function is called when we have a
static Value *GetLoadValueForLoad(LoadInst *SrcVal, unsigned Offset,
Type *LoadTy, Instruction *InsertPt,
GVN &gvn) {
- const DataLayout &TD = *gvn.getDataLayout();
+ const DataLayout &DL = *gvn.getDataLayout();
// If Offset+LoadTy exceeds the size of SrcVal, then we must be wanting to
// widen SrcVal out to a larger load.
- unsigned SrcValSize = TD.getTypeStoreSize(SrcVal->getType());
- unsigned LoadSize = TD.getTypeStoreSize(LoadTy);
+ unsigned SrcValSize = DL.getTypeStoreSize(SrcVal->getType());
+ unsigned LoadSize = DL.getTypeStoreSize(LoadTy);
if (Offset+LoadSize > SrcValSize) {
assert(SrcVal->isSimple() && "Cannot widen volatile/atomic load!");
assert(SrcVal->getType()->isIntegerTy() && "Can't widen non-integer load");
Type *DestPTy =
IntegerType::get(LoadTy->getContext(), NewLoadSize*8);
DestPTy = PointerType::get(DestPTy,
- cast<PointerType>(PtrVal->getType())->getAddressSpace());
+ PtrVal->getType()->getPointerAddressSpace());
Builder.SetCurrentDebugLocation(SrcVal->getDebugLoc());
PtrVal = Builder.CreateBitCast(PtrVal, DestPTy);
LoadInst *NewLoad = Builder.CreateLoad(PtrVal);
// Replace uses of the original load with the wider load. On a big endian
// system, we need to shift down to get the relevant bits.
Value *RV = NewLoad;
- if (TD.isBigEndian())
+ if (DL.isBigEndian())
RV = Builder.CreateLShr(RV,
NewLoadSize*8-SrcVal->getType()->getPrimitiveSizeInBits());
RV = Builder.CreateTrunc(RV, SrcVal->getType());
SrcVal = NewLoad;
}
- return GetStoreValueForLoad(SrcVal, Offset, LoadTy, InsertPt, TD);
+ return GetStoreValueForLoad(SrcVal, Offset, LoadTy, InsertPt, DL);
}
/// memdep query of a load that ends up being a clobbering mem intrinsic.
static Value *GetMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset,
Type *LoadTy, Instruction *InsertPt,
- const DataLayout &TD){
+ const DataLayout &DL){
LLVMContext &Ctx = LoadTy->getContext();
- uint64_t LoadSize = TD.getTypeSizeInBits(LoadTy)/8;
+ uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy)/8;
IRBuilder<> Builder(InsertPt->getParent(), InsertPt);
++NumBytesSet;
}
- return CoerceAvailableValueToLoadType(Val, LoadTy, InsertPt, TD);
+ return CoerceAvailableValueToLoadType(Val, LoadTy, InsertPt, DL);
}
// Otherwise, this is a memcpy/memmove from a constant global.
MemTransferInst *MTI = cast<MemTransferInst>(SrcInst);
Constant *Src = cast<Constant>(MTI->getSource());
+ unsigned AS = Src->getType()->getPointerAddressSpace();
// Otherwise, see if we can constant fold a load from the constant with the
// offset applied as appropriate.
Src = ConstantExpr::getBitCast(Src,
- llvm::Type::getInt8PtrTy(Src->getContext()));
+ Type::getInt8PtrTy(Src->getContext(), AS));
Constant *OffsetCst =
- ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
+ ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
Src = ConstantExpr::getGetElementPtr(Src, OffsetCst);
- Src = ConstantExpr::getBitCast(Src, PointerType::getUnqual(LoadTy));
- return ConstantFoldLoadFromConstPtr(Src, &TD);
+ Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
+ return ConstantFoldLoadFromConstPtr(Src, &DL);
}
-namespace {
-
-struct AvailableValueInBlock {
- /// BB - The basic block in question.
- BasicBlock *BB;
- enum ValType {
- SimpleVal, // A simple offsetted value that is accessed.
- LoadVal, // A value produced by a load.
- MemIntrin // A memory intrinsic which is loaded from.
- };
-
- /// V - The value that is live out of the block.
- PointerIntPair<Value *, 2, ValType> Val;
-
- /// Offset - The byte offset in Val that is interesting for the load query.
- unsigned Offset;
-
- static AvailableValueInBlock get(BasicBlock *BB, Value *V,
- unsigned Offset = 0) {
- AvailableValueInBlock Res;
- Res.BB = BB;
- Res.Val.setPointer(V);
- Res.Val.setInt(SimpleVal);
- Res.Offset = Offset;
- return Res;
- }
-
- static AvailableValueInBlock getMI(BasicBlock *BB, MemIntrinsic *MI,
- unsigned Offset = 0) {
- AvailableValueInBlock Res;
- Res.BB = BB;
- Res.Val.setPointer(MI);
- Res.Val.setInt(MemIntrin);
- Res.Offset = Offset;
- return Res;
- }
-
- static AvailableValueInBlock getLoad(BasicBlock *BB, LoadInst *LI,
- unsigned Offset = 0) {
- AvailableValueInBlock Res;
- Res.BB = BB;
- Res.Val.setPointer(LI);
- Res.Val.setInt(LoadVal);
- Res.Offset = Offset;
- return Res;
- }
-
- bool isSimpleValue() const { return Val.getInt() == SimpleVal; }
- bool isCoercedLoadValue() const { return Val.getInt() == LoadVal; }
- bool isMemIntrinValue() const { return Val.getInt() == MemIntrin; }
-
- Value *getSimpleValue() const {
- assert(isSimpleValue() && "Wrong accessor");
- return Val.getPointer();
- }
-
- LoadInst *getCoercedLoadValue() const {
- assert(isCoercedLoadValue() && "Wrong accessor");
- return cast<LoadInst>(Val.getPointer());
- }
-
- MemIntrinsic *getMemIntrinValue() const {
- assert(isMemIntrinValue() && "Wrong accessor");
- return cast<MemIntrinsic>(Val.getPointer());
- }
-
- /// MaterializeAdjustedValue - Emit code into this block to adjust the value
- /// defined here to the specified type. This handles various coercion cases.
- Value *MaterializeAdjustedValue(Type *LoadTy, GVN &gvn) const {
- Value *Res;
- if (isSimpleValue()) {
- Res = getSimpleValue();
- if (Res->getType() != LoadTy) {
- const DataLayout *TD = gvn.getDataLayout();
- assert(TD && "Need target data to handle type mismatch case");
- Res = GetStoreValueForLoad(Res, Offset, LoadTy, BB->getTerminator(),
- *TD);
-
- DEBUG(dbgs() << "GVN COERCED NONLOCAL VAL:\nOffset: " << Offset << " "
- << *getSimpleValue() << '\n'
- << *Res << '\n' << "\n\n\n");
- }
- } else if (isCoercedLoadValue()) {
- LoadInst *Load = getCoercedLoadValue();
- if (Load->getType() == LoadTy && Offset == 0) {
- Res = Load;
- } else {
- Res = GetLoadValueForLoad(Load, Offset, LoadTy, BB->getTerminator(),
- gvn);
-
- DEBUG(dbgs() << "GVN COERCED NONLOCAL LOAD:\nOffset: " << Offset << " "
- << *getCoercedLoadValue() << '\n'
- << *Res << '\n' << "\n\n\n");
- }
- } else {
- const DataLayout *TD = gvn.getDataLayout();
- assert(TD && "Need target data to handle type mismatch case");
- Res = GetMemInstValueForLoad(getMemIntrinValue(), Offset,
- LoadTy, BB->getTerminator(), *TD);
- DEBUG(dbgs() << "GVN COERCED NONLOCAL MEM INTRIN:\nOffset: " << Offset
- << " " << *getMemIntrinValue() << '\n'
- << *Res << '\n' << "\n\n\n");
- }
- return Res;
- }
-};
-
-} // end anonymous namespace
/// ConstructSSAForLoadSet - Given a set of loads specified by ValuesPerBlock,
/// construct SSA form, allowing us to eliminate LI. This returns the value
// just use the dominating value directly.
if (ValuesPerBlock.size() == 1 &&
gvn.getDominatorTree().properlyDominates(ValuesPerBlock[0].BB,
- LI->getParent()))
+ LI->getParent())) {
+ assert(!ValuesPerBlock[0].isUndefValue() && "Dead BB dominate this block");
return ValuesPerBlock[0].MaterializeAdjustedValue(LI->getType(), gvn);
+ }
// Otherwise, we have to construct SSA form.
SmallVector<PHINode*, 8> NewPHIs;
Value *V = SSAUpdate.GetValueInMiddleOfBlock(LI->getParent());
// If new PHI nodes were created, notify alias analysis.
- if (V->getType()->isPointerTy()) {
+ if (V->getType()->getScalarType()->isPointerTy()) {
AliasAnalysis *AA = gvn.getAliasAnalysis();
for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
return V;
}
+Value *AvailableValueInBlock::MaterializeAdjustedValue(Type *LoadTy, GVN &gvn) const {
+ Value *Res;
+ if (isSimpleValue()) {
+ Res = getSimpleValue();
+ if (Res->getType() != LoadTy) {
+ const DataLayout *DL = gvn.getDataLayout();
+ assert(DL && "Need target data to handle type mismatch case");
+ Res = GetStoreValueForLoad(Res, Offset, LoadTy, BB->getTerminator(),
+ *DL);
+
+ DEBUG(dbgs() << "GVN COERCED NONLOCAL VAL:\nOffset: " << Offset << " "
+ << *getSimpleValue() << '\n'
+ << *Res << '\n' << "\n\n\n");
+ }
+ } else if (isCoercedLoadValue()) {
+ LoadInst *Load = getCoercedLoadValue();
+ if (Load->getType() == LoadTy && Offset == 0) {
+ Res = Load;
+ } else {
+ Res = GetLoadValueForLoad(Load, Offset, LoadTy, BB->getTerminator(),
+ gvn);
+
+ DEBUG(dbgs() << "GVN COERCED NONLOCAL LOAD:\nOffset: " << Offset << " "
+ << *getCoercedLoadValue() << '\n'
+ << *Res << '\n' << "\n\n\n");
+ }
+ } else if (isMemIntrinValue()) {
+ const DataLayout *DL = gvn.getDataLayout();
+ assert(DL && "Need target data to handle type mismatch case");
+ Res = GetMemInstValueForLoad(getMemIntrinValue(), Offset,
+ LoadTy, BB->getTerminator(), *DL);
+ DEBUG(dbgs() << "GVN COERCED NONLOCAL MEM INTRIN:\nOffset: " << Offset
+ << " " << *getMemIntrinValue() << '\n'
+ << *Res << '\n' << "\n\n\n");
+ } else {
+ assert(isUndefValue() && "Should be UndefVal");
+ DEBUG(dbgs() << "GVN COERCED NONLOCAL Undef:\n";);
+ return UndefValue::get(LoadTy);
+ }
+ return Res;
+}
+
static bool isLifetimeStart(const Instruction *Inst) {
if (const IntrinsicInst* II = dyn_cast<IntrinsicInst>(Inst))
return II->getIntrinsicID() == Intrinsic::lifetime_start;
return false;
}
-/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are
-/// non-local by performing PHI construction.
-bool GVN::processNonLocalLoad(LoadInst *LI) {
- // Find the non-local dependencies of the load.
- SmallVector<NonLocalDepResult, 64> Deps;
- AliasAnalysis::Location Loc = VN.getAliasAnalysis()->getLocation(LI);
- MD->getNonLocalPointerDependency(Loc, true, LI->getParent(), Deps);
- //DEBUG(dbgs() << "INVESTIGATING NONLOCAL LOAD: "
- // << Deps.size() << *LI << '\n');
-
- // If we had to process more than one hundred blocks to find the
- // dependencies, this load isn't worth worrying about. Optimizing
- // it will be too expensive.
- unsigned NumDeps = Deps.size();
- if (NumDeps > 100)
- return false;
-
- // If we had a phi translation failure, we'll have a single entry which is a
- // clobber in the current block. Reject this early.
- if (NumDeps == 1 &&
- !Deps[0].getResult().isDef() && !Deps[0].getResult().isClobber()) {
- DEBUG(
- dbgs() << "GVN: non-local load ";
- WriteAsOperand(dbgs(), LI);
- dbgs() << " has unknown dependencies\n";
- );
- return false;
- }
+void GVN::AnalyzeLoadAvailability(LoadInst *LI, LoadDepVect &Deps,
+ AvailValInBlkVect &ValuesPerBlock,
+ UnavailBlkVect &UnavailableBlocks) {
// Filter out useless results (non-locals, etc). Keep track of the blocks
// where we have a value available in repl, also keep track of whether we see
// dependencies that produce an unknown value for the load (such as a call
// that could potentially clobber the load).
- SmallVector<AvailableValueInBlock, 64> ValuesPerBlock;
- SmallVector<BasicBlock*, 64> UnavailableBlocks;
-
+ unsigned NumDeps = Deps.size();
for (unsigned i = 0, e = NumDeps; i != e; ++i) {
BasicBlock *DepBB = Deps[i].getBB();
MemDepResult DepInfo = Deps[i].getResult();
+ if (DeadBlocks.count(DepBB)) {
+ // Dead dependent mem-op disguise as a load evaluating the same value
+ // as the load in question.
+ ValuesPerBlock.push_back(AvailableValueInBlock::getUndef(DepBB));
+ continue;
+ }
+
if (!DepInfo.isDef() && !DepInfo.isClobber()) {
UnavailableBlocks.push_back(DepBB);
continue;
// read by the load, we can extract the bits we need for the load from the
// stored value.
if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInfo.getInst())) {
- if (TD && Address) {
+ if (DL && Address) {
int Offset = AnalyzeLoadFromClobberingStore(LI->getType(), Address,
- DepSI, *TD);
+ DepSI, *DL);
if (Offset != -1) {
ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
DepSI->getValueOperand(),
if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInfo.getInst())) {
// If this is a clobber and L is the first instruction in its block, then
// we have the first instruction in the entry block.
- if (DepLI != LI && Address && TD) {
- int Offset = AnalyzeLoadFromClobberingLoad(LI->getType(),
- LI->getPointerOperand(),
- DepLI, *TD);
+ if (DepLI != LI && Address && DL) {
+ int Offset = AnalyzeLoadFromClobberingLoad(LI->getType(), Address,
+ DepLI, *DL);
if (Offset != -1) {
ValuesPerBlock.push_back(AvailableValueInBlock::getLoad(DepBB,DepLI,
// If the clobbering value is a memset/memcpy/memmove, see if we can
// forward a value on from it.
if (MemIntrinsic *DepMI = dyn_cast<MemIntrinsic>(DepInfo.getInst())) {
- if (TD && Address) {
+ if (DL && Address) {
int Offset = AnalyzeLoadFromClobberingMemInst(LI->getType(), Address,
- DepMI, *TD);
+ DepMI, *DL);
if (Offset != -1) {
ValuesPerBlock.push_back(AvailableValueInBlock::getMI(DepBB, DepMI,
Offset));
continue;
}
+ // Loading from calloc (which zero initializes memory) -> zero
+ if (isCallocLikeFn(DepInst, TLI)) {
+ ValuesPerBlock.push_back(AvailableValueInBlock::get(
+ DepBB, Constant::getNullValue(LI->getType())));
+ continue;
+ }
+
if (StoreInst *S = dyn_cast<StoreInst>(DepInst)) {
// Reject loads and stores that are to the same address but are of
// different types if we have to.
if (S->getValueOperand()->getType() != LI->getType()) {
// If the stored value is larger or equal to the loaded value, we can
// reuse it.
- if (TD == 0 || !CanCoerceMustAliasedValueToLoad(S->getValueOperand(),
- LI->getType(), *TD)) {
+ if (!DL || !CanCoerceMustAliasedValueToLoad(S->getValueOperand(),
+ LI->getType(), *DL)) {
UnavailableBlocks.push_back(DepBB);
continue;
}
if (LD->getType() != LI->getType()) {
// If the stored value is larger or equal to the loaded value, we can
// reuse it.
- if (TD == 0 || !CanCoerceMustAliasedValueToLoad(LD, LI->getType(),*TD)){
+ if (!DL || !CanCoerceMustAliasedValueToLoad(LD, LI->getType(),*DL)) {
UnavailableBlocks.push_back(DepBB);
continue;
}
}
UnavailableBlocks.push_back(DepBB);
- continue;
}
+}
- // If we have no predecessors that produce a known value for this load, exit
- // early.
- if (ValuesPerBlock.empty()) return false;
-
- // If all of the instructions we depend on produce a known value for this
- // load, then it is fully redundant and we can use PHI insertion to compute
- // its value. Insert PHIs and remove the fully redundant value now.
- if (UnavailableBlocks.empty()) {
- DEBUG(dbgs() << "GVN REMOVING NONLOCAL LOAD: " << *LI << '\n');
-
- // Perform PHI construction.
- Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, *this);
- LI->replaceAllUsesWith(V);
-
- if (isa<PHINode>(V))
- V->takeName(LI);
- if (V->getType()->isPointerTy())
- MD->invalidateCachedPointerInfo(V);
- markInstructionForDeletion(LI);
- ++NumGVNLoad;
- return true;
- }
-
- if (!EnablePRE || !EnableLoadPRE)
- return false;
-
+bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
+ UnavailBlkVect &UnavailableBlocks) {
// Okay, we have *some* definitions of the value. This means that the value
// is available in some of our (transitive) predecessors. Lets think about
// doing PRE of this load. This will involve inserting a new load into the
BasicBlock *LoadBB = LI->getParent();
BasicBlock *TmpBB = LoadBB;
- bool isSinglePred = false;
- bool allSingleSucc = true;
while (TmpBB->getSinglePredecessor()) {
- isSinglePred = true;
TmpBB = TmpBB->getSinglePredecessor();
if (TmpBB == LoadBB) // Infinite (unreachable) loop.
return false;
assert(TmpBB);
LoadBB = TmpBB;
- // FIXME: It is extremely unclear what this loop is doing, other than
- // artificially restricting loadpre.
- if (isSinglePred) {
- bool isHot = false;
- for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) {
- const AvailableValueInBlock &AV = ValuesPerBlock[i];
- if (AV.isSimpleValue())
- // "Hot" Instruction is in some loop (because it dominates its dep.
- // instruction).
- if (Instruction *I = dyn_cast<Instruction>(AV.getSimpleValue()))
- if (DT->dominates(LI, I)) {
- isHot = true;
- break;
- }
- }
-
- // We are interested only in "hot" instructions. We don't want to do any
- // mis-optimizations here.
- if (!isHot)
- return false;
- }
-
// Check to see how many predecessors have the loaded value fully
// available.
- DenseMap<BasicBlock*, Value*> PredLoads;
+ MapVector<BasicBlock *, Value *> PredLoads;
DenseMap<BasicBlock*, char> FullyAvailableBlocks;
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
FullyAvailableBlocks[ValuesPerBlock[i].BB] = true;
for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
FullyAvailableBlocks[UnavailableBlocks[i]] = false;
- SmallVector<std::pair<TerminatorInst*, unsigned>, 4> NeedToSplit;
+ SmallVector<BasicBlock *, 4> CriticalEdgePred;
for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
PI != E; ++PI) {
BasicBlock *Pred = *PI;
if (IsValueFullyAvailableInBlock(Pred, FullyAvailableBlocks, 0)) {
continue;
}
- PredLoads[Pred] = 0;
if (Pred->getTerminator()->getNumSuccessors() != 1) {
if (isa<IndirectBrInst>(Pred->getTerminator())) {
return false;
}
- unsigned SuccNum = GetSuccessorNumber(Pred, LoadBB);
- NeedToSplit.push_back(std::make_pair(Pred->getTerminator(), SuccNum));
+ CriticalEdgePred.push_back(Pred);
+ } else {
+ // Only add the predecessors that will not be split for now.
+ PredLoads[Pred] = nullptr;
}
}
- if (!NeedToSplit.empty()) {
- toSplit.append(NeedToSplit.begin(), NeedToSplit.end());
- return false;
- }
-
// Decide whether PRE is profitable for this load.
- unsigned NumUnavailablePreds = PredLoads.size();
+ unsigned NumUnavailablePreds = PredLoads.size() + CriticalEdgePred.size();
assert(NumUnavailablePreds != 0 &&
- "Fully available value should be eliminated above!");
+ "Fully available value should already be eliminated!");
// If this load is unavailable in multiple predecessors, reject it.
// FIXME: If we could restructure the CFG, we could make a common pred with
if (NumUnavailablePreds != 1)
return false;
+ // Split critical edges, and update the unavailable predecessors accordingly.
+ for (BasicBlock *OrigPred : CriticalEdgePred) {
+ BasicBlock *NewPred = splitCriticalEdges(OrigPred, LoadBB);
+ assert(!PredLoads.count(OrigPred) && "Split edges shouldn't be in map!");
+ PredLoads[NewPred] = nullptr;
+ DEBUG(dbgs() << "Split critical edge " << OrigPred->getName() << "->"
+ << LoadBB->getName() << '\n');
+ }
+
// Check if the load can safely be moved to all the unavailable predecessors.
bool CanDoPRE = true;
SmallVector<Instruction*, 8> NewInsts;
- for (DenseMap<BasicBlock*, Value*>::iterator I = PredLoads.begin(),
- E = PredLoads.end(); I != E; ++I) {
- BasicBlock *UnavailablePred = I->first;
+ for (auto &PredLoad : PredLoads) {
+ BasicBlock *UnavailablePred = PredLoad.first;
// Do PHI translation to get its value in the predecessor if necessary. The
// returned pointer (if non-null) is guaranteed to dominate UnavailablePred.
// If all preds have a single successor, then we know it is safe to insert
// the load on the pred (?!?), so we can insert code to materialize the
// pointer if it is not available.
- PHITransAddr Address(LI->getPointerOperand(), TD);
- Value *LoadPtr = 0;
- if (allSingleSucc) {
- LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred,
- *DT, NewInsts);
- } else {
- Address.PHITranslateValue(LoadBB, UnavailablePred, DT);
- LoadPtr = Address.getAddr();
- }
+ PHITransAddr Address(LI->getPointerOperand(), DL);
+ Value *LoadPtr = nullptr;
+ LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred,
+ *DT, NewInsts);
// If we couldn't find or insert a computation of this phi translated value,
// we fail PRE.
- if (LoadPtr == 0) {
+ if (!LoadPtr) {
DEBUG(dbgs() << "COULDN'T INSERT PHI TRANSLATED VALUE OF: "
<< *LI->getPointerOperand() << "\n");
CanDoPRE = false;
break;
}
- // Make sure it is valid to move this load here. We have to watch out for:
- // @1 = getelementptr (i8* p, ...
- // test p and branch if == 0
- // load @1
- // It is valid to have the getelementptr before the test, even if p can
- // be 0, as getelementptr only does address arithmetic.
- // If we are not pushing the value through any multiple-successor blocks
- // we do not have this case. Otherwise, check that the load is safe to
- // put anywhere; this can be improved, but should be conservatively safe.
- if (!allSingleSucc &&
- // FIXME: REEVALUTE THIS.
- !isSafeToLoadUnconditionally(LoadPtr,
- UnavailablePred->getTerminator(),
- LI->getAlignment(), TD)) {
- CanDoPRE = false;
- break;
- }
-
- I->second = LoadPtr;
+ PredLoad.second = LoadPtr;
}
if (!CanDoPRE) {
if (MD) MD->removeInstruction(I);
I->eraseFromParent();
}
- return false;
+ // HINT: Don't revert the edge-splitting as following transformation may
+ // also need to split these critical edges.
+ return !CriticalEdgePred.empty();
}
// Okay, we can eliminate this load by inserting a reload in the predecessor
VN.lookup_or_add(NewInsts[i]);
}
- for (DenseMap<BasicBlock*, Value*>::iterator I = PredLoads.begin(),
- E = PredLoads.end(); I != E; ++I) {
- BasicBlock *UnavailablePred = I->first;
- Value *LoadPtr = I->second;
+ for (const auto &PredLoad : PredLoads) {
+ BasicBlock *UnavailablePred = PredLoad.first;
+ Value *LoadPtr = PredLoad.second;
Instruction *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
LI->getAlignment(),
UnavailablePred->getTerminator());
- // Transfer the old load's TBAA tag to the new load.
- if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa))
- NewLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
+ // Transfer the old load's AA tags to the new load.
+ AAMDNodes Tags;
+ LI->getAAMetadata(Tags);
+ if (Tags)
+ NewLoad->setAAMetadata(Tags);
// Transfer DebugLoc.
NewLoad->setDebugLoc(LI->getDebugLoc());
LI->replaceAllUsesWith(V);
if (isa<PHINode>(V))
V->takeName(LI);
- if (V->getType()->isPointerTy())
+ if (V->getType()->getScalarType()->isPointerTy())
MD->invalidateCachedPointerInfo(V);
markInstructionForDeletion(LI);
++NumPRELoad;
return true;
}
-static void patchReplacementInstruction(Value *Repl, Instruction *I) {
+/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are
+/// non-local by performing PHI construction.
+bool GVN::processNonLocalLoad(LoadInst *LI) {
+ // Step 1: Find the non-local dependencies of the load.
+ LoadDepVect Deps;
+ AliasAnalysis::Location Loc = VN.getAliasAnalysis()->getLocation(LI);
+ MD->getNonLocalPointerDependency(Loc, true, LI->getParent(), Deps);
+
+ // If we had to process more than one hundred blocks to find the
+ // dependencies, this load isn't worth worrying about. Optimizing
+ // it will be too expensive.
+ unsigned NumDeps = Deps.size();
+ if (NumDeps > 100)
+ return false;
+
+ // If we had a phi translation failure, we'll have a single entry which is a
+ // clobber in the current block. Reject this early.
+ if (NumDeps == 1 &&
+ !Deps[0].getResult().isDef() && !Deps[0].getResult().isClobber()) {
+ DEBUG(
+ dbgs() << "GVN: non-local load ";
+ LI->printAsOperand(dbgs());
+ dbgs() << " has unknown dependencies\n";
+ );
+ return false;
+ }
+
+ // Step 2: Analyze the availability of the load
+ AvailValInBlkVect ValuesPerBlock;
+ UnavailBlkVect UnavailableBlocks;
+ AnalyzeLoadAvailability(LI, Deps, ValuesPerBlock, UnavailableBlocks);
+
+ // If we have no predecessors that produce a known value for this load, exit
+ // early.
+ if (ValuesPerBlock.empty())
+ return false;
+
+ // Step 3: Eliminate fully redundancy.
+ //
+ // If all of the instructions we depend on produce a known value for this
+ // load, then it is fully redundant and we can use PHI insertion to compute
+ // its value. Insert PHIs and remove the fully redundant value now.
+ if (UnavailableBlocks.empty()) {
+ DEBUG(dbgs() << "GVN REMOVING NONLOCAL LOAD: " << *LI << '\n');
+
+ // Perform PHI construction.
+ Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, *this);
+ LI->replaceAllUsesWith(V);
+
+ if (isa<PHINode>(V))
+ V->takeName(LI);
+ if (V->getType()->getScalarType()->isPointerTy())
+ MD->invalidateCachedPointerInfo(V);
+ markInstructionForDeletion(LI);
+ ++NumGVNLoad;
+ return true;
+ }
+
+ // Step 4: Eliminate partial redundancy.
+ if (!EnablePRE || !EnableLoadPRE)
+ return false;
+
+ return PerformLoadPRE(LI, ValuesPerBlock, UnavailableBlocks);
+}
+
+
+static void patchReplacementInstruction(Instruction *I, Value *Repl) {
// Patch the replacement so that it is not more restrictive than the value
// being replaced.
BinaryOperator *Op = dyn_cast<BinaryOperator>(I);
ReplOp->setHasNoUnsignedWrap(false);
}
if (Instruction *ReplInst = dyn_cast<Instruction>(Repl)) {
- SmallVector<std::pair<unsigned, MDNode*>, 4> Metadata;
- ReplInst->getAllMetadataOtherThanDebugLoc(Metadata);
- for (int i = 0, n = Metadata.size(); i < n; ++i) {
- unsigned Kind = Metadata[i].first;
- MDNode *IMD = I->getMetadata(Kind);
- MDNode *ReplMD = Metadata[i].second;
- switch(Kind) {
- default:
- ReplInst->setMetadata(Kind, NULL); // Remove unknown metadata
- break;
- case LLVMContext::MD_dbg:
- llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
- case LLVMContext::MD_tbaa:
- ReplInst->setMetadata(Kind, MDNode::getMostGenericTBAA(IMD, ReplMD));
- break;
- case LLVMContext::MD_range:
- ReplInst->setMetadata(Kind, MDNode::getMostGenericRange(IMD, ReplMD));
- break;
- case LLVMContext::MD_prof:
- llvm_unreachable("MD_prof in a non terminator instruction");
- break;
- case LLVMContext::MD_fpmath:
- ReplInst->setMetadata(Kind, MDNode::getMostGenericFPMath(IMD, ReplMD));
- break;
- }
- }
+ // FIXME: If both the original and replacement value are part of the
+ // same control-flow region (meaning that the execution of one
+ // guarentees the executation of the other), then we can combine the
+ // noalias scopes here and do better than the general conservative
+ // answer used in combineMetadata().
+
+ // In general, GVN unifies expressions over different control-flow
+ // regions, and so we need a conservative combination of the noalias
+ // scopes.
+ unsigned KnownIDs[] = {
+ LLVMContext::MD_tbaa,
+ LLVMContext::MD_alias_scope,
+ LLVMContext::MD_noalias,
+ LLVMContext::MD_range,
+ LLVMContext::MD_fpmath,
+ LLVMContext::MD_invariant_load,
+ };
+ combineMetadata(ReplInst, I, KnownIDs);
}
}
-static void patchAndReplaceAllUsesWith(Value *Repl, Instruction *I) {
- patchReplacementInstruction(Repl, I);
+static void patchAndReplaceAllUsesWith(Instruction *I, Value *Repl) {
+ patchReplacementInstruction(I, Repl);
I->replaceAllUsesWith(Repl);
}
// If we have a clobber and target data is around, see if this is a clobber
// that we can fix up through code synthesis.
- if (Dep.isClobber() && TD) {
+ if (Dep.isClobber() && DL) {
// Check to see if we have something like this:
// store i32 123, i32* %P
// %A = bitcast i32* %P to i8*
// a common base + constant offset, and if the previous store (or memset)
// completely covers this load. This sort of thing can happen in bitfield
// access code.
- Value *AvailVal = 0;
+ Value *AvailVal = nullptr;
if (StoreInst *DepSI = dyn_cast<StoreInst>(Dep.getInst())) {
int Offset = AnalyzeLoadFromClobberingStore(L->getType(),
L->getPointerOperand(),
- DepSI, *TD);
+ DepSI, *DL);
if (Offset != -1)
AvailVal = GetStoreValueForLoad(DepSI->getValueOperand(), Offset,
- L->getType(), L, *TD);
+ L->getType(), L, *DL);
}
// Check to see if we have something like this:
int Offset = AnalyzeLoadFromClobberingLoad(L->getType(),
L->getPointerOperand(),
- DepLI, *TD);
+ DepLI, *DL);
if (Offset != -1)
AvailVal = GetLoadValueForLoad(DepLI, Offset, L->getType(), L, *this);
}
if (MemIntrinsic *DepMI = dyn_cast<MemIntrinsic>(Dep.getInst())) {
int Offset = AnalyzeLoadFromClobberingMemInst(L->getType(),
L->getPointerOperand(),
- DepMI, *TD);
+ DepMI, *DL);
if (Offset != -1)
- AvailVal = GetMemInstValueForLoad(DepMI, Offset, L->getType(), L, *TD);
+ AvailVal = GetMemInstValueForLoad(DepMI, Offset, L->getType(), L, *DL);
}
if (AvailVal) {
// Replace the load!
L->replaceAllUsesWith(AvailVal);
- if (AvailVal->getType()->isPointerTy())
+ if (AvailVal->getType()->getScalarType()->isPointerTy())
MD->invalidateCachedPointerInfo(AvailVal);
markInstructionForDeletion(L);
++NumGVNLoad;
DEBUG(
// fast print dep, using operator<< on instruction is too slow.
dbgs() << "GVN: load ";
- WriteAsOperand(dbgs(), L);
+ L->printAsOperand(dbgs());
Instruction *I = Dep.getInst();
dbgs() << " is clobbered by " << *I << '\n';
);
DEBUG(
// fast print dep, using operator<< on instruction is too slow.
dbgs() << "GVN: load ";
- WriteAsOperand(dbgs(), L);
+ L->printAsOperand(dbgs());
dbgs() << " has unknown dependence\n";
);
return false;
// actually have the same type. See if we know how to reuse the stored
// value (depending on its type).
if (StoredVal->getType() != L->getType()) {
- if (TD) {
+ if (DL) {
StoredVal = CoerceAvailableValueToLoadType(StoredVal, L->getType(),
- L, *TD);
- if (StoredVal == 0)
+ L, *DL);
+ if (!StoredVal)
return false;
DEBUG(dbgs() << "GVN COERCED STORE:\n" << *DepSI << '\n' << *StoredVal
// Remove it!
L->replaceAllUsesWith(StoredVal);
- if (StoredVal->getType()->isPointerTy())
+ if (StoredVal->getType()->getScalarType()->isPointerTy())
MD->invalidateCachedPointerInfo(StoredVal);
markInstructionForDeletion(L);
++NumGVNLoad;
// the same type. See if we know how to reuse the previously loaded value
// (depending on its type).
if (DepLI->getType() != L->getType()) {
- if (TD) {
+ if (DL) {
AvailableVal = CoerceAvailableValueToLoadType(DepLI, L->getType(),
- L, *TD);
- if (AvailableVal == 0)
+ L, *DL);
+ if (!AvailableVal)
return false;
DEBUG(dbgs() << "GVN COERCED LOAD:\n" << *DepLI << "\n" << *AvailableVal
}
// Remove it!
- patchAndReplaceAllUsesWith(AvailableVal, L);
- if (DepLI->getType()->isPointerTy())
+ patchAndReplaceAllUsesWith(L, AvailableVal);
+ if (DepLI->getType()->getScalarType()->isPointerTy())
MD->invalidateCachedPointerInfo(DepLI);
markInstructionForDeletion(L);
++NumGVNLoad;
}
}
+ // If this load follows a calloc (which zero initializes memory),
+ // then the loaded value is zero
+ if (isCallocLikeFn(DepInst, TLI)) {
+ L->replaceAllUsesWith(Constant::getNullValue(L->getType()));
+ markInstructionForDeletion(L);
+ ++NumGVNLoad;
+ return true;
+ }
+
return false;
}
// a few comparisons of DFS numbers.
Value *GVN::findLeader(const BasicBlock *BB, uint32_t num) {
LeaderTableEntry Vals = LeaderTable[num];
- if (!Vals.Val) return 0;
+ if (!Vals.Val) return nullptr;
- Value *Val = 0;
+ Value *Val = nullptr;
if (DT->dominates(Vals.BB, BB)) {
Val = Vals.Val;
if (isa<Constant>(Val)) return Val;
unsigned Count = 0;
for (Value::use_iterator UI = From->use_begin(), UE = From->use_end();
UI != UE; ) {
- Use &U = (UI++).getUse();
+ Use &U = *UI++;
if (DT->dominates(Root, U)) {
U.set(To);
const BasicBlock *Src = E.getStart();
assert((!Pred || Pred == Src) && "No edge between these basic blocks!");
(void)Src;
- return Pred != 0;
+ return Pred != nullptr;
}
/// propagateEquality - The given values are known to be equal in every block
// to value numbering it. Value numbering often exposes redundancies, for
// example if it determines that %y is equal to %x then the instruction
// "%z = and i32 %x, %y" becomes "%z = and i32 %x, %x" which we now simplify.
- if (Value *V = SimplifyInstruction(I, TD, TLI, DT)) {
+ if (Value *V = SimplifyInstruction(I, DL, TLI, DT)) {
I->replaceAllUsesWith(V);
- if (MD && V->getType()->isPointerTy())
+ if (MD && V->getType()->getScalarType()->isPointerTy())
MD->invalidateCachedPointerInfo(V);
markInstructionForDeletion(I);
++NumGVNSimpl;
// For conditional branches, we can perform simple conditional propagation on
// the condition value itself.
if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
- if (!BI->isConditional() || isa<Constant>(BI->getCondition()))
+ if (!BI->isConditional())
return false;
- Value *BranchCond = BI->getCondition();
+ if (isa<Constant>(BI->getCondition()))
+ return processFoldableCondBr(BI);
+ Value *BranchCond = BI->getCondition();
BasicBlock *TrueSucc = BI->getSuccessor(0);
BasicBlock *FalseSucc = BI->getSuccessor(1);
// Avoid multiple edges early.
// Perform fast-path value-number based elimination of values inherited from
// dominators.
Value *repl = findLeader(I->getParent(), Num);
- if (repl == 0) {
+ if (!repl) {
// Failure, just remember this instance for future use.
addToLeaderTable(Num, I, I->getParent());
return false;
}
// Remove it!
- patchAndReplaceAllUsesWith(repl, I);
- if (MD && repl->getType()->isPointerTy())
+ patchAndReplaceAllUsesWith(I, repl);
+ if (MD && repl->getType()->getScalarType()->isPointerTy())
MD->invalidateCachedPointerInfo(repl);
markInstructionForDeletion(I);
return true;
/// runOnFunction - This is the main transformation entry point for a function.
bool GVN::runOnFunction(Function& F) {
+ if (skipOptnoneFunction(F))
+ return false;
+
if (!NoLoads)
MD = &getAnalysis<MemoryDependenceAnalysis>();
- DT = &getAnalysis<DominatorTree>();
- TD = getAnalysisIfAvailable<DataLayout>();
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
+ DL = DLP ? &DLP->getDataLayout() : nullptr;
TLI = &getAnalysis<TargetLibraryInfo>();
VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>());
VN.setMemDep(MD);
while (ShouldContinue) {
DEBUG(dbgs() << "GVN iteration: " << Iteration << "\n");
ShouldContinue = iterateOnFunction(F);
- if (splitCriticalEdges())
- ShouldContinue = true;
Changed |= ShouldContinue;
++Iteration;
}
if (EnablePRE) {
+ // Fabricate val-num for dead-code in order to suppress assertion in
+ // performPRE().
+ assignValNumForDeadCode();
bool PREChanged = true;
while (PREChanged) {
PREChanged = performPRE(F);
Changed |= PREChanged;
}
}
+
// FIXME: Should perform GVN again after PRE does something. PRE can move
// computations into blocks where they become fully redundant. Note that
// we can't do this until PRE's critical edge splitting updates memdep.
// Actually, when this happens, we should just fully integrate PRE into GVN.
cleanupGlobalSets();
+ // Do not cleanup DeadBlocks in cleanupGlobalSets() as it's called for each
+ // iteration.
+ DeadBlocks.clear();
return Changed;
}
// (and incrementing BI before processing an instruction).
assert(InstrsToErase.empty() &&
"We expect InstrsToErase to be empty across iterations");
+ if (DeadBlocks.count(BB))
+ return false;
+
bool ChangedFunction = false;
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
if (!AtStart)
--BI;
- for (SmallVector<Instruction*, 4>::iterator I = InstrsToErase.begin(),
+ for (SmallVectorImpl<Instruction *>::iterator I = InstrsToErase.begin(),
E = InstrsToErase.end(); I != E; ++I) {
DEBUG(dbgs() << "GVN removed: " << **I << '\n');
if (MD) MD->removeInstruction(*I);
- (*I)->eraseFromParent();
DEBUG(verifyRemoved(*I));
+ (*I)->eraseFromParent();
}
InstrsToErase.clear();
/// control flow patterns and attempts to perform simple PRE at the join point.
bool GVN::performPRE(Function &F) {
bool Changed = false;
- DenseMap<BasicBlock*, Value*> predMap;
- for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
- DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) {
- BasicBlock *CurrentBlock = *DI;
-
+ SmallVector<std::pair<Value*, BasicBlock*>, 8> predMap;
+ for (BasicBlock *CurrentBlock : depth_first(&F.getEntryBlock())) {
// Nothing to PRE in the entry block.
if (CurrentBlock == &F.getEntryBlock()) continue;
// more complicated to get right.
unsigned NumWith = 0;
unsigned NumWithout = 0;
- BasicBlock *PREPred = 0;
+ BasicBlock *PREPred = nullptr;
predMap.clear();
for (pred_iterator PI = pred_begin(CurrentBlock),
if (P == CurrentBlock) {
NumWithout = 2;
break;
- } else if (!DT->dominates(&F.getEntryBlock(), P)) {
+ } else if (!DT->isReachableFromEntry(P)) {
NumWithout = 2;
break;
}
Value* predV = findLeader(P, ValNo);
- if (predV == 0) {
+ if (!predV) {
+ predMap.push_back(std::make_pair(static_cast<Value *>(nullptr), P));
PREPred = P;
++NumWithout;
} else if (predV == CurInst) {
+ /* CurInst dominates this predecessor. */
NumWithout = 2;
+ break;
} else {
- predMap[P] = predV;
+ predMap.push_back(std::make_pair(predV, P));
++NumWith;
}
}
// the PRE predecessor. This is typically because of loads which
// are not value numbered precisely.
if (!success) {
- delete PREInstr;
DEBUG(verifyRemoved(PREInstr));
+ delete PREInstr;
continue;
}
PREInstr->insertBefore(PREPred->getTerminator());
PREInstr->setName(CurInst->getName() + ".pre");
PREInstr->setDebugLoc(CurInst->getDebugLoc());
- predMap[PREPred] = PREInstr;
VN.add(PREInstr, ValNo);
++NumGVNPRE;
addToLeaderTable(ValNo, PREInstr, PREPred);
// Create a PHI to make the value available in this block.
- pred_iterator PB = pred_begin(CurrentBlock), PE = pred_end(CurrentBlock);
- PHINode* Phi = PHINode::Create(CurInst->getType(), std::distance(PB, PE),
+ PHINode* Phi = PHINode::Create(CurInst->getType(), predMap.size(),
CurInst->getName() + ".pre-phi",
CurrentBlock->begin());
- for (pred_iterator PI = PB; PI != PE; ++PI) {
- BasicBlock *P = *PI;
- Phi->addIncoming(predMap[P], P);
+ for (unsigned i = 0, e = predMap.size(); i != e; ++i) {
+ if (Value *V = predMap[i].first)
+ Phi->addIncoming(V, predMap[i].second);
+ else
+ Phi->addIncoming(PREInstr, PREPred);
}
VN.add(Phi, ValNo);
addToLeaderTable(ValNo, Phi, CurrentBlock);
Phi->setDebugLoc(CurInst->getDebugLoc());
CurInst->replaceAllUsesWith(Phi);
- if (Phi->getType()->isPointerTy()) {
+ if (Phi->getType()->getScalarType()->isPointerTy()) {
// Because we have added a PHI-use of the pointer value, it has now
// "escaped" from alias analysis' perspective. We need to inform
// AA of this.
DEBUG(dbgs() << "GVN PRE removed: " << *CurInst << '\n');
if (MD) MD->removeInstruction(CurInst);
- CurInst->eraseFromParent();
DEBUG(verifyRemoved(CurInst));
+ CurInst->eraseFromParent();
Changed = true;
}
}
return Changed;
}
+/// Split the critical edge connecting the given two blocks, and return
+/// the block inserted to the critical edge.
+BasicBlock *GVN::splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ) {
+ BasicBlock *BB = SplitCriticalEdge(Pred, Succ, this);
+ if (MD)
+ MD->invalidateCachedPredecessors();
+ return BB;
+}
+
/// splitCriticalEdges - Split critical edges found during the previous
/// iteration that may enable further optimization.
bool GVN::splitCriticalEdges() {
RE = RPOT.end(); RI != RE; ++RI)
Changed |= processBlock(*RI);
#else
- for (df_iterator<DomTreeNode*> DI = df_begin(DT->getRootNode()),
- DE = df_end(DT->getRootNode()); DI != DE; ++DI)
- Changed |= processBlock(DI->getBlock());
+ // Save the blocks this function have before transformation begins. GVN may
+ // split critical edge, and hence may invalidate the RPO/DT iterator.
+ //
+ std::vector<BasicBlock *> BBVect;
+ BBVect.reserve(256);
+ for (DomTreeNode *x : depth_first(DT->getRootNode()))
+ BBVect.push_back(x->getBlock());
+
+ for (std::vector<BasicBlock *>::iterator I = BBVect.begin(), E = BBVect.end();
+ I != E; I++)
+ Changed |= processBlock(*I);
#endif
return Changed;
}
}
}
+
+// BB is declared dead, which implied other blocks become dead as well. This
+// function is to add all these blocks to "DeadBlocks". For the dead blocks'
+// live successors, update their phi nodes by replacing the operands
+// corresponding to dead blocks with UndefVal.
+//
+void GVN::addDeadBlock(BasicBlock *BB) {
+ SmallVector<BasicBlock *, 4> NewDead;
+ SmallSetVector<BasicBlock *, 4> DF;
+
+ NewDead.push_back(BB);
+ while (!NewDead.empty()) {
+ BasicBlock *D = NewDead.pop_back_val();
+ if (DeadBlocks.count(D))
+ continue;
+
+ // All blocks dominated by D are dead.
+ SmallVector<BasicBlock *, 8> Dom;
+ DT->getDescendants(D, Dom);
+ DeadBlocks.insert(Dom.begin(), Dom.end());
+
+ // Figure out the dominance-frontier(D).
+ for (SmallVectorImpl<BasicBlock *>::iterator I = Dom.begin(),
+ E = Dom.end(); I != E; I++) {
+ BasicBlock *B = *I;
+ for (succ_iterator SI = succ_begin(B), SE = succ_end(B); SI != SE; SI++) {
+ BasicBlock *S = *SI;
+ if (DeadBlocks.count(S))
+ continue;
+
+ bool AllPredDead = true;
+ for (pred_iterator PI = pred_begin(S), PE = pred_end(S); PI != PE; PI++)
+ if (!DeadBlocks.count(*PI)) {
+ AllPredDead = false;
+ break;
+ }
+
+ if (!AllPredDead) {
+ // S could be proved dead later on. That is why we don't update phi
+ // operands at this moment.
+ DF.insert(S);
+ } else {
+ // While S is not dominated by D, it is dead by now. This could take
+ // place if S already have a dead predecessor before D is declared
+ // dead.
+ NewDead.push_back(S);
+ }
+ }
+ }
+ }
+
+ // For the dead blocks' live successors, update their phi nodes by replacing
+ // the operands corresponding to dead blocks with UndefVal.
+ for(SmallSetVector<BasicBlock *, 4>::iterator I = DF.begin(), E = DF.end();
+ I != E; I++) {
+ BasicBlock *B = *I;
+ if (DeadBlocks.count(B))
+ continue;
+
+ SmallVector<BasicBlock *, 4> Preds(pred_begin(B), pred_end(B));
+ for (SmallVectorImpl<BasicBlock *>::iterator PI = Preds.begin(),
+ PE = Preds.end(); PI != PE; PI++) {
+ BasicBlock *P = *PI;
+
+ if (!DeadBlocks.count(P))
+ continue;
+
+ if (isCriticalEdge(P->getTerminator(), GetSuccessorNumber(P, B))) {
+ if (BasicBlock *S = splitCriticalEdges(P, B))
+ DeadBlocks.insert(P = S);
+ }
+
+ for (BasicBlock::iterator II = B->begin(); isa<PHINode>(II); ++II) {
+ PHINode &Phi = cast<PHINode>(*II);
+ Phi.setIncomingValue(Phi.getBasicBlockIndex(P),
+ UndefValue::get(Phi.getType()));
+ }
+ }
+ }
+}
+
+// If the given branch is recognized as a foldable branch (i.e. conditional
+// branch with constant condition), it will perform following analyses and
+// transformation.
+// 1) If the dead out-coming edge is a critical-edge, split it. Let
+// R be the target of the dead out-coming edge.
+// 1) Identify the set of dead blocks implied by the branch's dead outcoming
+// edge. The result of this step will be {X| X is dominated by R}
+// 2) Identify those blocks which haves at least one dead prodecessor. The
+// result of this step will be dominance-frontier(R).
+// 3) Update the PHIs in DF(R) by replacing the operands corresponding to
+// dead blocks with "UndefVal" in an hope these PHIs will optimized away.
+//
+// Return true iff *NEW* dead code are found.
+bool GVN::processFoldableCondBr(BranchInst *BI) {
+ if (!BI || BI->isUnconditional())
+ return false;
+
+ ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
+ if (!Cond)
+ return false;
+
+ BasicBlock *DeadRoot = Cond->getZExtValue() ?
+ BI->getSuccessor(1) : BI->getSuccessor(0);
+ if (DeadBlocks.count(DeadRoot))
+ return false;
+
+ if (!DeadRoot->getSinglePredecessor())
+ DeadRoot = splitCriticalEdges(BI->getParent(), DeadRoot);
+
+ addDeadBlock(DeadRoot);
+ return true;
+}
+
+// performPRE() will trigger assert if it comes across an instruction without
+// associated val-num. As it normally has far more live instructions than dead
+// instructions, it makes more sense just to "fabricate" a val-number for the
+// dead code than checking if instruction involved is dead or not.
+void GVN::assignValNumForDeadCode() {
+ for (SetVector<BasicBlock *>::iterator I = DeadBlocks.begin(),
+ E = DeadBlocks.end(); I != E; I++) {
+ BasicBlock *BB = *I;
+ for (BasicBlock::iterator II = BB->begin(), EE = BB->end();
+ II != EE; II++) {
+ Instruction *Inst = &*II;
+ unsigned ValNum = VN.lookup_or_add(Inst);
+ addToLeaderTable(ValNum, Inst, BB);
+ }
+ }
+}
projects / oota-llvm.git / blobdiff