#define DEBUG_TYPE "memcpyopt"
#include "llvm/Transforms/Scalar.h"
+#include "llvm/GlobalVariable.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Instructions.h"
-#include "llvm/LLVMContext.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/Target/TargetLibraryInfo.h"
#include <list>
using namespace llvm;
STATISTIC(NumMemCpyInstr, "Number of memcpy instructions deleted");
STATISTIC(NumMemSetInfer, "Number of memsets inferred");
STATISTIC(NumMoveToCpy, "Number of memmoves converted to memcpy");
-
-/// isBytewiseValue - If the specified value can be set by repeating the same
-/// byte in memory, return the i8 value that it is represented with. This is
-/// true for all i8 values obviously, but is also true for i32 0, i32 -1,
-/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated
-/// byte store (e.g. i16 0x1234), return null.
-static Value *isBytewiseValue(Value *V) {
- LLVMContext &Context = V->getContext();
-
- // All byte-wide stores are splatable, even of arbitrary variables.
- if (V->getType()->isIntegerTy(8)) return V;
-
- // Constant float and double values can be handled as integer values if the
- // corresponding integer value is "byteable". An important case is 0.0.
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
- if (CFP->getType()->isFloatTy())
- V = ConstantExpr::getBitCast(CFP, Type::getInt32Ty(Context));
- if (CFP->getType()->isDoubleTy())
- V = ConstantExpr::getBitCast(CFP, Type::getInt64Ty(Context));
- // Don't handle long double formats, which have strange constraints.
- }
-
- // We can handle constant integers that are power of two in size and a
- // multiple of 8 bits.
- if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
- unsigned Width = CI->getBitWidth();
- if (isPowerOf2_32(Width) && Width > 8) {
- // We can handle this value if the recursive binary decomposition is the
- // same at all levels.
- APInt Val = CI->getValue();
- APInt Val2;
- while (Val.getBitWidth() != 8) {
- unsigned NextWidth = Val.getBitWidth()/2;
- Val2 = Val.lshr(NextWidth);
- Val2.trunc(Val.getBitWidth()/2);
- Val.trunc(Val.getBitWidth()/2);
-
- // If the top/bottom halves aren't the same, reject it.
- if (Val != Val2)
- return 0;
- }
- return ConstantInt::get(Context, Val);
- }
- }
-
- // Conceptually, we could handle things like:
- // %a = zext i8 %X to i16
- // %b = shl i16 %a, 8
- // %c = or i16 %a, %b
- // but until there is an example that actually needs this, it doesn't seem
- // worth worrying about.
- return 0;
-}
+STATISTIC(NumCpyToSet, "Number of memcpys converted to memset");
static int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx,
- bool &VariableIdxFound, TargetData &TD) {
+ bool &VariableIdxFound, const TargetData &TD){
// Skip over the first indices.
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1; i != Idx; ++i, ++GTI)
if (OpC->isZero()) continue; // No offset.
// Handle struct indices, which add their field offset to the pointer.
- if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
+ if (StructType *STy = dyn_cast<StructType>(*GTI)) {
Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
continue;
}
/// constant offset, and return that constant offset. For example, Ptr1 might
/// be &A[42], and Ptr2 might be &A[40]. In this case offset would be -8.
static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
- TargetData &TD) {
+ const TargetData &TD) {
+ Ptr1 = Ptr1->stripPointerCasts();
+ Ptr2 = Ptr2->stripPointerCasts();
+ GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(Ptr1);
+ GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(Ptr2);
+
+ bool VariableIdxFound = false;
+
+ // If one pointer is a GEP and the other isn't, then see if the GEP is a
+ // constant offset from the base, as in "P" and "gep P, 1".
+ if (GEP1 && GEP2 == 0 && GEP1->getOperand(0)->stripPointerCasts() == Ptr2) {
+ Offset = -GetOffsetFromIndex(GEP1, 1, VariableIdxFound, TD);
+ return !VariableIdxFound;
+ }
+
+ if (GEP2 && GEP1 == 0 && GEP2->getOperand(0)->stripPointerCasts() == Ptr1) {
+ Offset = GetOffsetFromIndex(GEP2, 1, VariableIdxFound, TD);
+ return !VariableIdxFound;
+ }
+
// Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical
// base. After that base, they may have some number of common (and
// potentially variable) indices. After that they handle some constant
// offset, which determines their offset from each other. At this point, we
// handle no other case.
- GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(Ptr1);
- GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(Ptr2);
if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0))
return false;
if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx))
break;
- bool VariableIdxFound = false;
int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, TD);
int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, TD);
if (VariableIdxFound) return false;
unsigned Alignment;
/// TheStores - The actual stores that make up this range.
- SmallVector<StoreInst*, 16> TheStores;
+ SmallVector<Instruction*, 16> TheStores;
bool isProfitableToUseMemset(const TargetData &TD) const;
} // end anon namespace
bool MemsetRange::isProfitableToUseMemset(const TargetData &TD) const {
- // If we found more than 8 stores to merge or 64 bytes, use memset.
- if (TheStores.size() >= 8 || End-Start >= 64) return true;
+ // If we found more than 4 stores to merge or 16 bytes, use memset.
+ if (TheStores.size() >= 4 || End-Start >= 16) return true;
+
+ // If there is nothing to merge, don't do anything.
+ if (TheStores.size() < 2) return false;
+
+ // If any of the stores are a memset, then it is always good to extend the
+ // memset.
+ for (unsigned i = 0, e = TheStores.size(); i != e; ++i)
+ if (!isa<StoreInst>(TheStores[i]))
+ return true;
// Assume that the code generator is capable of merging pairs of stores
// together if it wants to.
- if (TheStores.size() <= 2) return false;
+ if (TheStores.size() == 2) return false;
// If we have fewer than 8 stores, it can still be worthwhile to do this.
// For example, merging 4 i8 stores into an i32 store is useful almost always.
/// because each element is relatively large and expensive to copy.
std::list<MemsetRange> Ranges;
typedef std::list<MemsetRange>::iterator range_iterator;
- TargetData &TD;
+ const TargetData &TD;
public:
- MemsetRanges(TargetData &td) : TD(td) {}
+ MemsetRanges(const TargetData &td) : TD(td) {}
typedef std::list<MemsetRange>::const_iterator const_iterator;
const_iterator begin() const { return Ranges.begin(); }
const_iterator end() const { return Ranges.end(); }
bool empty() const { return Ranges.empty(); }
- void addStore(int64_t OffsetFromFirst, StoreInst *SI);
+ void addInst(int64_t OffsetFromFirst, Instruction *Inst) {
+ if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
+ addStore(OffsetFromFirst, SI);
+ else
+ addMemSet(OffsetFromFirst, cast<MemSetInst>(Inst));
+ }
+
+ void addStore(int64_t OffsetFromFirst, StoreInst *SI) {
+ int64_t StoreSize = TD.getTypeStoreSize(SI->getOperand(0)->getType());
+
+ addRange(OffsetFromFirst, StoreSize,
+ SI->getPointerOperand(), SI->getAlignment(), SI);
+ }
+
+ void addMemSet(int64_t OffsetFromFirst, MemSetInst *MSI) {
+ int64_t Size = cast<ConstantInt>(MSI->getLength())->getZExtValue();
+ addRange(OffsetFromFirst, Size, MSI->getDest(), MSI->getAlignment(), MSI);
+ }
+
+ void addRange(int64_t Start, int64_t Size, Value *Ptr,
+ unsigned Alignment, Instruction *Inst);
+
};
} // end anon namespace
-/// addStore - Add a new store to the MemsetRanges data structure. This adds a
+/// addRange - Add a new store to the MemsetRanges data structure. This adds a
/// new range for the specified store at the specified offset, merging into
/// existing ranges as appropriate.
-void MemsetRanges::addStore(int64_t Start, StoreInst *SI) {
- int64_t End = Start+TD.getTypeStoreSize(SI->getOperand(0)->getType());
-
- // Do a linear search of the ranges to see if this can be joined and/or to
- // find the insertion point in the list. We keep the ranges sorted for
- // simplicity here. This is a linear search of a linked list, which is ugly,
- // however the number of ranges is limited, so this won't get crazy slow.
+///
+/// Do a linear search of the ranges to see if this can be joined and/or to
+/// find the insertion point in the list. We keep the ranges sorted for
+/// simplicity here. This is a linear search of a linked list, which is ugly,
+/// however the number of ranges is limited, so this won't get crazy slow.
+void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
+ unsigned Alignment, Instruction *Inst) {
+ int64_t End = Start+Size;
range_iterator I = Ranges.begin(), E = Ranges.end();
while (I != E && Start > I->End)
MemsetRange &R = *Ranges.insert(I, MemsetRange());
R.Start = Start;
R.End = End;
- R.StartPtr = SI->getPointerOperand();
- R.Alignment = SI->getAlignment();
- R.TheStores.push_back(SI);
+ R.StartPtr = Ptr;
+ R.Alignment = Alignment;
+ R.TheStores.push_back(Inst);
return;
}
-
+
// This store overlaps with I, add it.
- I->TheStores.push_back(SI);
+ I->TheStores.push_back(Inst);
// At this point, we may have an interval that completely contains our store.
// If so, just add it to the interval and return.
// stopped on *it*.
if (Start < I->Start) {
I->Start = Start;
- I->StartPtr = SI->getPointerOperand();
- I->Alignment = SI->getAlignment();
+ I->StartPtr = Ptr;
+ I->Alignment = Alignment;
}
// Now we know that Start <= I->End and Start >= I->Start (so the startpoint
namespace {
class MemCpyOpt : public FunctionPass {
- bool runOnFunction(Function &F);
+ MemoryDependenceAnalysis *MD;
+ TargetLibraryInfo *TLI;
+ const TargetData *TD;
public:
static char ID; // Pass identification, replacement for typeid
- MemCpyOpt() : FunctionPass(&ID) {}
+ MemCpyOpt() : FunctionPass(ID) {
+ initializeMemCpyOptPass(*PassRegistry::getPassRegistry());
+ MD = 0;
+ TLI = 0;
+ TD = 0;
+ }
+
+ bool runOnFunction(Function &F);
private:
// This transformation requires dominator postdominator info
AU.addRequired<DominatorTree>();
AU.addRequired<MemoryDependenceAnalysis>();
AU.addRequired<AliasAnalysis>();
+ AU.addRequired<TargetLibraryInfo>();
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<MemoryDependenceAnalysis>();
}
// Helper fuctions
bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
+ bool processMemSet(MemSetInst *SI, BasicBlock::iterator &BBI);
bool processMemCpy(MemCpyInst *M);
bool processMemMove(MemMoveInst *M);
- bool performCallSlotOptzn(MemCpyInst *cpy, CallInst *C);
+ bool performCallSlotOptzn(Instruction *cpy, Value *cpyDst, Value *cpySrc,
+ uint64_t cpyLen, CallInst *C);
+ bool processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
+ uint64_t MSize);
+ bool processByValArgument(CallSite CS, unsigned ArgNo);
+ Instruction *tryMergingIntoMemset(Instruction *I, Value *StartPtr,
+ Value *ByteVal);
+
bool iterateOnFunction(Function &F);
};
// createMemCpyOptPass - The public interface to this file...
FunctionPass *llvm::createMemCpyOptPass() { return new MemCpyOpt(); }
-INITIALIZE_PASS(MemCpyOpt, "memcpyopt", "MemCpy Optimization", false, false);
-
+INITIALIZE_PASS_BEGIN(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
+ false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_END(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
+ false, false)
-
-/// processStore - When GVN is scanning forward over instructions, we look for
+/// tryMergingIntoMemset - When scanning forward over instructions, we look for
/// some other patterns to fold away. In particular, this looks for stores to
-/// neighboring locations of memory. If it sees enough consequtive ones
-/// (currently 4) it attempts to merge them together into a memcpy/memset.
-bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
- if (SI->isVolatile()) return false;
-
- LLVMContext &Context = SI->getContext();
-
- // There are two cases that are interesting for this code to handle: memcpy
- // and memset. Right now we only handle memset.
+/// neighboring locations of memory. If it sees enough consecutive ones, it
+/// attempts to merge them together into a memcpy/memset.
+Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
+ Value *StartPtr, Value *ByteVal) {
+ if (TD == 0) return 0;
- // Ensure that the value being stored is something that can be memset'able a
- // byte at a time like "0" or "-1" or any width, as well as things like
- // 0xA0A0A0A0 and 0.0.
- Value *ByteVal = isBytewiseValue(SI->getOperand(0));
- if (!ByteVal)
- return false;
-
- TargetData *TD = getAnalysisIfAvailable<TargetData>();
- if (!TD) return false;
- AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- Module *M = SI->getParent()->getParent()->getParent();
-
// Okay, so we now have a single store that can be splatable. Scan to find
// all subsequent stores of the same value to offset from the same pointer.
// Join these together into ranges, so we can decide whether contiguous blocks
// are stored.
MemsetRanges Ranges(*TD);
- Value *StartPtr = SI->getPointerOperand();
-
- BasicBlock::iterator BI = SI;
+ BasicBlock::iterator BI = StartInst;
for (++BI; !isa<TerminatorInst>(BI); ++BI) {
- if (isa<CallInst>(BI) || isa<InvokeInst>(BI)) {
- // If the call is readnone, ignore it, otherwise bail out. We don't even
- // allow readonly here because we don't want something like:
+ if (!isa<StoreInst>(BI) && !isa<MemSetInst>(BI)) {
+ // If the instruction is readnone, ignore it, otherwise bail out. We
+ // don't even allow readonly here because we don't want something like:
// A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
- if (AA.getModRefBehavior(CallSite::get(BI)) ==
- AliasAnalysis::DoesNotAccessMemory)
- continue;
-
- // TODO: If this is a memset, try to join it in.
-
- break;
- } else if (isa<VAArgInst>(BI) || isa<LoadInst>(BI))
- break;
-
- // If this is a non-store instruction it is fine, ignore it.
- StoreInst *NextStore = dyn_cast<StoreInst>(BI);
- if (NextStore == 0) continue;
+ if (BI->mayWriteToMemory() || BI->mayReadFromMemory())
+ break;
+ continue;
+ }
- // If this is a store, see if we can merge it in.
- if (NextStore->isVolatile()) break;
+ if (StoreInst *NextStore = dyn_cast<StoreInst>(BI)) {
+ // If this is a store, see if we can merge it in.
+ if (!NextStore->isSimple()) break;
- // Check to see if this stored value is of the same byte-splattable value.
- if (ByteVal != isBytewiseValue(NextStore->getOperand(0)))
- break;
-
- // Check to see if this store is to a constant offset from the start ptr.
- int64_t Offset;
- if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(), Offset, *TD))
- break;
-
- Ranges.addStore(Offset, NextStore);
+ // Check to see if this stored value is of the same byte-splattable value.
+ if (ByteVal != isBytewiseValue(NextStore->getOperand(0)))
+ break;
+
+ // Check to see if this store is to a constant offset from the start ptr.
+ int64_t Offset;
+ if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(),
+ Offset, *TD))
+ break;
+
+ Ranges.addStore(Offset, NextStore);
+ } else {
+ MemSetInst *MSI = cast<MemSetInst>(BI);
+
+ if (MSI->isVolatile() || ByteVal != MSI->getValue() ||
+ !isa<ConstantInt>(MSI->getLength()))
+ break;
+
+ // Check to see if this store is to a constant offset from the start ptr.
+ int64_t Offset;
+ if (!IsPointerOffset(StartPtr, MSI->getDest(), Offset, *TD))
+ break;
+
+ Ranges.addMemSet(Offset, MSI);
+ }
}
-
+
// If we have no ranges, then we just had a single store with nothing that
// could be merged in. This is a very common case of course.
if (Ranges.empty())
- return false;
+ return 0;
// If we had at least one store that could be merged in, add the starting
// store as well. We try to avoid this unless there is at least something
// interesting as a small compile-time optimization.
- Ranges.addStore(0, SI);
-
-
+ Ranges.addInst(0, StartInst);
+
+ // If we create any memsets, we put it right before the first instruction that
+ // isn't part of the memset block. This ensure that the memset is dominated
+ // by any addressing instruction needed by the start of the block.
+ IRBuilder<> Builder(BI);
+
// Now that we have full information about ranges, loop over the ranges and
// emit memset's for anything big enough to be worthwhile.
- bool MadeChange = false;
+ Instruction *AMemSet = 0;
for (MemsetRanges::const_iterator I = Ranges.begin(), E = Ranges.end();
I != E; ++I) {
const MemsetRange &Range = *I;
-
+
if (Range.TheStores.size() == 1) continue;
// If it is profitable to lower this range to memset, do so now.
if (!Range.isProfitableToUseMemset(*TD))
continue;
- // Otherwise, we do want to transform this! Create a new memset. We put
- // the memset right before the first instruction that isn't part of this
- // memset block. This ensure that the memset is dominated by any addressing
- // instruction needed by the start of the block.
- BasicBlock::iterator InsertPt = BI;
-
+ // Otherwise, we do want to transform this! Create a new memset.
// Get the starting pointer of the block.
StartPtr = Range.StartPtr;
-
+
// Determine alignment
unsigned Alignment = Range.Alignment;
if (Alignment == 0) {
- const Type *EltType =
-
cast<PointerType>(StartPtr->getType())->getElementType();
+ Type *EltType =
+ cast<PointerType>(StartPtr->getType())->getElementType();
Alignment = TD->getABITypeAlignment(EltType);
}
-
- // Cast the start ptr to be i8* as memset requires.
- const PointerType* StartPTy = cast<PointerType>(StartPtr->getType());
- const PointerType *i8Ptr = Type::getInt8PtrTy(Context,
- StartPTy->getAddressSpace());
- if (StartPTy!= i8Ptr)
- StartPtr = new BitCastInst(StartPtr, i8Ptr, StartPtr->getName(),
- InsertPt);
-
- Value *Ops[] = {
- StartPtr, ByteVal, // Start, value
- // size
- ConstantInt::get(Type::getInt64Ty(Context), Range.End-Range.Start),
- // align
- ConstantInt::get(Type::getInt32Ty(Context), Alignment),
- // volatile
- ConstantInt::get(Type::getInt1Ty(Context), 0),
- };
- const Type *Tys[] = { Ops[0]->getType(), Ops[2]->getType() };
-
- Function *MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset, Tys, 2);
-
- Value *C = CallInst::Create(MemSetF, Ops, Ops+5, "", InsertPt);
+
+ AMemSet =
+ Builder.CreateMemSet(StartPtr, ByteVal, Range.End-Range.Start, Alignment);
+
DEBUG(dbgs() << "Replace stores:\n";
for (unsigned i = 0, e = Range.TheStores.size(); i != e; ++i)
- dbgs() << *Range.TheStores[i];
- dbgs() << "With: " << *C); C=C;
-
- // Don't invalidate the iterator
- BBI = BI;
-
+ dbgs() << *Range.TheStores[i] << '\n';
+ dbgs() << "With: " << *AMemSet << '\n');
+
+ if (!Range.TheStores.empty())
+ AMemSet->setDebugLoc(Range.TheStores[0]->getDebugLoc());
+
// Zap all the stores.
- for (SmallVector<StoreInst*, 16>::const_iterator
+ for (SmallVector<Instruction*, 16>::const_iterator
SI = Range.TheStores.begin(),
- SE = Range.TheStores.end(); SI != SE; ++SI)
+ SE = Range.TheStores.end(); SI != SE; ++SI) {
+ MD->removeInstruction(*SI);
(*SI)->eraseFromParent();
+ }
++NumMemSetInfer;
- MadeChange = true;
}
- return MadeChange;
+ return AMemSet;
+}
+
+
+bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
+ if (!SI->isSimple()) return false;
+
+ if (TD == 0) return false;
+
+ // Detect cases where we're performing call slot forwarding, but
+ // happen to be using a load-store pair to implement it, rather than
+ // a memcpy.
+ if (LoadInst *LI = dyn_cast<LoadInst>(SI->getOperand(0))) {
+ if (LI->isSimple() && LI->hasOneUse() &&
+ LI->getParent() == SI->getParent()) {
+ MemDepResult ldep = MD->getDependency(LI);
+ CallInst *C = 0;
+ if (ldep.isClobber() && !isa<MemCpyInst>(ldep.getInst()))
+ C = dyn_cast<CallInst>(ldep.getInst());
+
+ if (C) {
+ // Check that nothing touches the dest of the "copy" between
+ // the call and the store.
+ AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
+ AliasAnalysis::Location StoreLoc = AA.getLocation(SI);
+ for (BasicBlock::iterator I = --BasicBlock::iterator(SI),
+ E = C; I != E; --I) {
+ if (AA.getModRefInfo(&*I, StoreLoc) != AliasAnalysis::NoModRef) {
+ C = 0;
+ break;
+ }
+ }
+ }
+
+ if (C) {
+ bool changed = performCallSlotOptzn(LI,
+ SI->getPointerOperand()->stripPointerCasts(),
+ LI->getPointerOperand()->stripPointerCasts(),
+ TD->getTypeStoreSize(SI->getOperand(0)->getType()), C);
+ if (changed) {
+ MD->removeInstruction(SI);
+ SI->eraseFromParent();
+ MD->removeInstruction(LI);
+ LI->eraseFromParent();
+ ++NumMemCpyInstr;
+ return true;
+ }
+ }
+ }
+ }
+
+ // There are two cases that are interesting for this code to handle: memcpy
+ // and memset. Right now we only handle memset.
+
+ // Ensure that the value being stored is something that can be memset'able a
+ // byte at a time like "0" or "-1" or any width, as well as things like
+ // 0xA0A0A0A0 and 0.0.
+ if (Value *ByteVal = isBytewiseValue(SI->getOperand(0)))
+ if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
+ ByteVal)) {
+ BBI = I; // Don't invalidate iterator.
+ return true;
+ }
+
+ return false;
+}
+
+bool MemCpyOpt::processMemSet(MemSetInst *MSI, BasicBlock::iterator &BBI) {
+ // See if there is another memset or store neighboring this memset which
+ // allows us to widen out the memset to do a single larger store.
+ if (isa<ConstantInt>(MSI->getLength()) && !MSI->isVolatile())
+ if (Instruction *I = tryMergingIntoMemset(MSI, MSI->getDest(),
+ MSI->getValue())) {
+ BBI = I; // Don't invalidate iterator.
+ return true;
+ }
+ return false;
}
/// performCallSlotOptzn - takes a memcpy and a call that it depends on,
/// and checks for the possibility of a call slot optimization by having
/// the call write its result directly into the destination of the memcpy.
-bool MemCpyOpt::performCallSlotOptzn(MemCpyInst *cpy, CallInst *C) {
+bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
+ Value *cpyDest, Value *cpySrc,
+ uint64_t cpyLen, CallInst *C) {
// The general transformation to keep in mind is
//
// call @func(..., src, ...)
// Deliberately get the source and destination with bitcasts stripped away,
// because we'll need to do type comparisons based on the underlying type.
- Value *cpyDest = cpy->getDest();
- Value *cpySrc = cpy->getSource();
- CallSite CS = CallSite::get(C);
-
- // We need to be able to reason about the size of the memcpy, so we require
- // that it be a constant.
- ConstantInt *cpyLength = dyn_cast<ConstantInt>(cpy->getLength());
- if (!cpyLength)
- return false;
+ CallSite CS(C);
// Require that src be an alloca. This simplifies the reasoning considerably.
AllocaInst *srcAlloca = dyn_cast<AllocaInst>(cpySrc);
return false;
// Check that all of src is copied to dest.
- TargetData *TD = getAnalysisIfAvailable<TargetData>();
- if (!TD) return false;
+ if (TD == 0) return false;
ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
if (!srcArraySize)
uint64_t srcSize = TD->getTypeAllocSize(srcAlloca->getAllocatedType()) *
srcArraySize->getZExtValue();
- if (cpyLength->getZExtValue() < srcSize)
+ if (cpyLen < srcSize)
return false;
// Check that accessing the first srcSize bytes of dest will not cause a
if (!A->hasStructRetAttr())
return false;
-
const Type *StructTy = cast<PointerType>(A->getType())->getElementType();
+ Type *StructTy = cast<PointerType>(A->getType())->getElementType();
uint64_t destSize = TD->getTypeAllocSize(StructTy);
if (destSize < srcSize)
// the use analysis, we also need to know that it does not sneakily
// access dest. We rely on AA to figure this out for us.
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- if (AA.getModRefInfo(C, cpy->getRawDest(), srcSize) !=
- AliasAnalysis::NoModRef)
+ if (AA.getModRefInfo(C, cpyDest, srcSize) != AliasAnalysis::NoModRef)
return false;
// All the checks have passed, so do the transformation.
// Drop any cached information about the call, because we may have changed
// its dependence information by changing its parameter.
- MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>();
- MD.removeInstruction(C);
+ MD->removeInstruction(C);
- // Remove the memcpy
- MD.removeInstruction(cpy);
- cpy->eraseFromParent();
+ // Remove the memcpy.
+ MD->removeInstruction(cpy);
++NumMemCpyInstr;
return true;
}
-/// processMemCpy - perform simplication of memcpy's. If we have memcpy A which
-/// copies X to Y, and memcpy B which copies Y to Z, then we can rewrite B to be
-/// a memcpy from X to Z (or potentially a memmove, depending on circumstances).
-/// This allows later passes to remove the first memcpy altogether.
-bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
- MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>();
-
- // The are two possible optimizations we can do for memcpy:
- // a) memcpy-memcpy xform which exposes redundance for DSE.
- // b) call-memcpy xform for return slot optimization.
- MemDepResult dep = MD.getDependency(M);
- if (!dep.isClobber())
- return false;
- if (!isa<MemCpyInst>(dep.getInst())) {
- if (CallInst *C = dyn_cast<CallInst>(dep.getInst()))
- return performCallSlotOptzn(M, C);
- return false;
- }
-
- MemCpyInst *MDep = cast<MemCpyInst>(dep.getInst());
-
+/// processMemCpyMemCpyDependence - We've found that the (upward scanning)
+/// memory dependence of memcpy 'M' is the memcpy 'MDep'. Try to simplify M to
+/// copy from MDep's input if we can. MSize is the size of M's copy.
+///
+bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
+ uint64_t MSize) {
// We can only transforms memcpy's where the dest of one is the source of the
- // other
- if (M->getSource() != MDep->getDest())
+ // other.
+ if (M->getSource() != MDep->getDest() || MDep->isVolatile())
return false;
- // Second, the length of the memcpy's must be the same, or the preceeding one
- // must be larger than the following one.
- ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength());
- ConstantInt *C2 = dyn_cast<ConstantInt>(M->getLength());
- if (!C1 || !C2)
+ // If dep instruction is reading from our current input, then it is a noop
+ // transfer and substituting the input won't change this instruction. Just
+ // ignore the input and let someone else zap MDep. This handles cases like:
+ // memcpy(a <- a)
+ // memcpy(b <- a)
+ if (M->getSource() == MDep->getSource())
return false;
- uint64_t DepSize = C1->getValue().getZExtValue();
- uint64_t CpySize = C2->getValue().getZExtValue();
-
- if (DepSize < CpySize)
+ // Second, the length of the memcpy's must be the same, or the preceding one
+ // must be larger than the following one.
+ ConstantInt *MDepLen = dyn_cast<ConstantInt>(MDep->getLength());
+ ConstantInt *MLen = dyn_cast<ConstantInt>(M->getLength());
+ if (!MDepLen || !MLen || MDepLen->getZExtValue() < MLen->getZExtValue())
return false;
- // Finally, we have to make sure that the dest of the second does not
- // alias the source of the first
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- if (AA.alias(M->getRawDest(), CpySize, MDep->getRawSource(), DepSize) !=
- AliasAnalysis::NoAlias)
- return false;
- else if (AA.alias(M->getRawDest(), CpySize, M->getRawSource(), CpySize) !=
- AliasAnalysis::NoAlias)
- return false;
- else if (AA.alias(MDep->getRawDest(), DepSize, MDep->getRawSource(), DepSize)
- != AliasAnalysis::NoAlias)
+
+ // Verify that the copied-from memory doesn't change in between the two
+ // transfers. For example, in:
+ // memcpy(a <- b)
+ // *b = 42;
+ // memcpy(c <- a)
+ // It would be invalid to transform the second memcpy into memcpy(c <- b).
+ //
+ // TODO: If the code between M and MDep is transparent to the destination "c",
+ // then we could still perform the xform by moving M up to the first memcpy.
+ //
+ // NOTE: This is conservative, it will stop on any read from the source loc,
+ // not just the defining memcpy.
+ MemDepResult SourceDep =
+ MD->getPointerDependencyFrom(AA.getLocationForSource(MDep),
+ false, M, M->getParent());
+ if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
return false;
- // If all checks passed, then we can transform these memcpy's
- const Type *ArgTys[3] = { M->getRawDest()->getType(),
- MDep->getRawSource()->getType(),
- M->getLength()->getType() };
- Function *MemCpyFun = Intrinsic::getDeclaration(
- M->getParent()->getParent()->getParent(),
- M->getIntrinsicID(), ArgTys, 3);
-
- Value *Args[5] = {
- M->getRawDest(), MDep->getRawSource(), M->getLength(),
- M->getAlignmentCst(), M->getVolatileCst()
- };
-
- CallInst *C = CallInst::Create(MemCpyFun, Args, Args+5, "", M);
-
-
- // If C and M don't interfere, then this is a valid transformation. If they
- // did, this would mean that the two sources overlap, which would be bad.
- if (MD.getDependency(C) == dep) {
- MD.removeInstruction(M);
+ // If the dest of the second might alias the source of the first, then the
+ // source and dest might overlap. We still want to eliminate the intermediate
+ // value, but we have to generate a memmove instead of memcpy.
+ bool UseMemMove = false;
+ if (!AA.isNoAlias(AA.getLocationForDest(M), AA.getLocationForSource(MDep)))
+ UseMemMove = true;
+
+ // If all checks passed, then we can transform M.
+
+ // Make sure to use the lesser of the alignment of the source and the dest
+ // since we're changing where we're reading from, but don't want to increase
+ // the alignment past what can be read from or written to.
+ // TODO: Is this worth it if we're creating a less aligned memcpy? For
+ // example we could be moving from movaps -> movq on x86.
+ unsigned Align = std::min(MDep->getAlignment(), M->getAlignment());
+
+ IRBuilder<> Builder(M);
+ if (UseMemMove)
+ Builder.CreateMemMove(M->getRawDest(), MDep->getRawSource(), M->getLength(),
+ Align, M->isVolatile());
+ else
+ Builder.CreateMemCpy(M->getRawDest(), MDep->getRawSource(), M->getLength(),
+ Align, M->isVolatile());
+
+ // Remove the instruction we're replacing.
+ MD->removeInstruction(M);
+ M->eraseFromParent();
+ ++NumMemCpyInstr;
+ return true;
+}
+
+
+/// processMemCpy - perform simplification of memcpy's. If we have memcpy A
+/// which copies X to Y, and memcpy B which copies Y to Z, then we can rewrite
+/// B to be a memcpy from X to Z (or potentially a memmove, depending on
+/// circumstances). This allows later passes to remove the first memcpy
+/// altogether.
+bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
+ // We can only optimize statically-sized memcpy's that are non-volatile.
+ ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
+ if (CopySize == 0 || M->isVolatile()) return false;
+
+ // If the source and destination of the memcpy are the same, then zap it.
+ if (M->getSource() == M->getDest()) {
+ MD->removeInstruction(M);
M->eraseFromParent();
- ++NumMemCpyInstr;
- return true;
+ return false;
}
-
- // Otherwise, there was no point in doing this, so we remove the call we
- // inserted and act like nothing happened.
- MD.removeInstruction(C);
- C->eraseFromParent();
+
+ // If copying from a constant, try to turn the memcpy into a memset.
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource()))
+ if (GV->isConstant() && GV->hasDefinitiveInitializer())
+ if (Value *ByteVal = isBytewiseValue(GV->getInitializer())) {
+ IRBuilder<> Builder(M);
+ Builder.CreateMemSet(M->getRawDest(), ByteVal, CopySize,
+ M->getAlignment(), false);
+ MD->removeInstruction(M);
+ M->eraseFromParent();
+ ++NumCpyToSet;
+ return true;
+ }
+
+ // The are two possible optimizations we can do for memcpy:
+ // a) memcpy-memcpy xform which exposes redundance for DSE.
+ // b) call-memcpy xform for return slot optimization.
+ MemDepResult DepInfo = MD->getDependency(M);
+ if (DepInfo.isClobber()) {
+ if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
+ if (performCallSlotOptzn(M, M->getDest(), M->getSource(),
+ CopySize->getZExtValue(), C)) {
+ MD->removeInstruction(M);
+ M->eraseFromParent();
+ return true;
+ }
+ }
+ }
+
+ AliasAnalysis::Location SrcLoc = AliasAnalysis::getLocationForSource(M);
+ MemDepResult SrcDepInfo = MD->getPointerDependencyFrom(SrcLoc, true,
+ M, M->getParent());
+ if (SrcDepInfo.isClobber()) {
+ if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst()))
+ return processMemCpyMemCpyDependence(M, MDep, CopySize->getZExtValue());
+ }
+
return false;
}
bool MemCpyOpt::processMemMove(MemMoveInst *M) {
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- // If the memmove is a constant size, use it for the alias query, this allows
- // us to optimize things like: memmove(P, P+64, 64);
- uint64_t MemMoveSize = ~0ULL;
- if (ConstantInt *Len = dyn_cast<ConstantInt>(M->getLength()))
- MemMoveSize = Len->getZExtValue();
+ if (!TLI->has(LibFunc::memmove))
+ return false;
// See if the pointers alias.
- if (AA.alias(M->getRawDest(), MemMoveSize, M->getRawSource(), MemMoveSize) !=
- AliasAnalysis::NoAlias)
+ if (!AA.isNoAlias(AA.getLocationForDest(M), AA.getLocationForSource(M)))
return false;
DEBUG(dbgs() << "MemCpyOpt: Optimizing memmove -> memcpy: " << *M << "\n");
// If not, then we know we can transform this.
Module *Mod = M->getParent()->getParent()->getParent();
- const Type *ArgTys[3] = { M->getRawDest()->getType(),
- M->getRawSource()->getType(),
- M->getLength()->getType() };
- M->setCalledFunction(Intrinsic::getDeclaration(Mod, Intrinsic::memcpy, ArgTys, 3));
+ Type *ArgTys[3] = { M->getRawDest()->getType(),
+ M->getRawSource()->getType(),
+ M->getLength()->getType() };
+ M->setCalledFunction(Intrinsic::getDeclaration(Mod, Intrinsic::memcpy,
+ ArgTys));
// MemDep may have over conservative information about this instruction, just
// conservatively flush it from the cache.
- getAnalysis<MemoryDependenceAnalysis>().removeInstruction(M);
+ MD->removeInstruction(M);
++NumMoveToCpy;
return true;
}
+/// processByValArgument - This is called on every byval argument in call sites.
+bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
+ if (TD == 0) return false;
+
+ // Find out what feeds this byval argument.
+ Value *ByValArg = CS.getArgument(ArgNo);
+ Type *ByValTy = cast<PointerType>(ByValArg->getType())->getElementType();
+ uint64_t ByValSize = TD->getTypeAllocSize(ByValTy);
+ MemDepResult DepInfo =
+ MD->getPointerDependencyFrom(AliasAnalysis::Location(ByValArg, ByValSize),
+ true, CS.getInstruction(),
+ CS.getInstruction()->getParent());
+ if (!DepInfo.isClobber())
+ return false;
+
+ // If the byval argument isn't fed by a memcpy, ignore it. If it is fed by
+ // a memcpy, see if we can byval from the source of the memcpy instead of the
+ // result.
+ MemCpyInst *MDep = dyn_cast<MemCpyInst>(DepInfo.getInst());
+ if (MDep == 0 || MDep->isVolatile() ||
+ ByValArg->stripPointerCasts() != MDep->getDest())
+ return false;
+
+ // The length of the memcpy must be larger or equal to the size of the byval.
+ ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength());
+ if (C1 == 0 || C1->getValue().getZExtValue() < ByValSize)
+ return false;
+
+ // Get the alignment of the byval. If the call doesn't specify the alignment,
+ // then it is some target specific value that we can't know.
+ unsigned ByValAlign = CS.getParamAlignment(ArgNo+1);
+ if (ByValAlign == 0) return false;
+
+ // If it is greater than the memcpy, then we check to see if we can force the
+ // source of the memcpy to the alignment we need. If we fail, we bail out.
+ if (MDep->getAlignment() < ByValAlign &&
+ getOrEnforceKnownAlignment(MDep->getSource(),ByValAlign, TD) < ByValAlign)
+ return false;
+
+ // Verify that the copied-from memory doesn't change in between the memcpy and
+ // the byval call.
+ // memcpy(a <- b)
+ // *b = 42;
+ // foo(*a)
+ // It would be invalid to transform the second memcpy into foo(*b).
+ //
+ // NOTE: This is conservative, it will stop on any read from the source loc,
+ // not just the defining memcpy.
+ MemDepResult SourceDep =
+ MD->getPointerDependencyFrom(AliasAnalysis::getLocationForSource(MDep),
+ false, CS.getInstruction(), MDep->getParent());
+ if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
+ return false;
+
+ Value *TmpCast = MDep->getSource();
+ if (MDep->getSource()->getType() != ByValArg->getType())
+ TmpCast = new BitCastInst(MDep->getSource(), ByValArg->getType(),
+ "tmpcast", CS.getInstruction());
+
+ DEBUG(dbgs() << "MemCpyOpt: Forwarding memcpy to byval:\n"
+ << " " << *MDep << "\n"
+ << " " << *CS.getInstruction() << "\n");
+
+ // Otherwise we're good! Update the byval argument.
+ CS.setArgument(ArgNo, TmpCast);
+ ++NumMemCpyInstr;
+ return true;
+}
-// MemCpyOpt::iterateOnFunction - Executes one iteration of GVN.
+/// iterateOnFunction - Executes one iteration of MemCpyOpt.
bool MemCpyOpt::iterateOnFunction(Function &F) {
bool MadeChange = false;
// Walk all instruction in the function.
for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) {
- for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
- BI != BE;) {
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
// Avoid invalidating the iterator.
Instruction *I = BI++;
+ bool RepeatInstruction = false;
+
if (StoreInst *SI = dyn_cast<StoreInst>(I))
MadeChange |= processStore(SI, BI);
+ else if (MemSetInst *M = dyn_cast<MemSetInst>(I))
+ RepeatInstruction = processMemSet(M, BI);
else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I))
- MadeChange |= processMemCpy(M);
- else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I)) {
- if (processMemMove(M)) {
- --BI; // Reprocess the new memcpy.
- MadeChange = true;
- }
+ RepeatInstruction = processMemCpy(M);
+ else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I))
+ RepeatInstruction = processMemMove(M);
+ else if (CallSite CS = (Value*)I) {
+ for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
+ if (CS.isByValArgument(i))
+ MadeChange |= processByValArgument(CS, i);
+ }
+
+ // Reprocess the instruction if desired.
+ if (RepeatInstruction) {
+ if (BI != BB->begin()) --BI;
+ MadeChange = true;
}
}
}
//
bool MemCpyOpt::runOnFunction(Function &F) {
bool MadeChange = false;
+ MD = &getAnalysis<MemoryDependenceAnalysis>();
+ TD = getAnalysisIfAvailable<TargetData>();
+ TLI = &getAnalysis<TargetLibraryInfo>();
+
+ // If we don't have at least memset and memcpy, there is little point of doing
+ // anything here. These are required by a freestanding implementation, so if
+ // even they are disabled, there is no point in trying hard.
+ if (!TLI->has(LibFunc::memset) || !TLI->has(LibFunc::memcpy))
+ return false;
+
while (1) {
if (!iterateOnFunction(F))
break;
MadeChange = true;
}
+ MD = 0;
return MadeChange;
}
-
-
-
projects / oota-llvm.git / blobdiff