//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "memcpyopt"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Instructions.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/GetElementPtrTypeIterator.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/Debug.h"
-#include "llvm/Support/GetElementPtrTypeIterator.h"
-#include "llvm/Target/TargetData.h"
-#include <list>
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include <algorithm>
using namespace llvm;
+#define DEBUG_TYPE "memcpyopt"
+
STATISTIC(NumMemCpyInstr, "Number of memcpy instructions deleted");
STATISTIC(NumMemSetInfer, "Number of memsets inferred");
+STATISTIC(NumMoveToCpy, "Number of memmoves converted to memcpy");
+STATISTIC(NumCpyToSet, "Number of memcpys converted to memset");
-/// 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) {
- // All byte-wide stores are splatable, even of arbitrary variables.
- if (V->getType() == Type::Int8Ty) 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() == Type::FloatTy)
- V = ConstantExpr::getBitCast(CFP, Type::Int32Ty);
- if (CFP->getType() == Type::DoubleTy)
- V = ConstantExpr::getBitCast(CFP, Type::Int64Ty);
- // 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(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;
-}
-
-static int64_t GetOffsetFromIndex(const GetElementPtrInst *GEP, unsigned Idx,
- bool &VariableIdxFound, TargetData &TD) {
+static int64_t GetOffsetFromIndex(const GEPOperator *GEP, unsigned Idx,
+ bool &VariableIdxFound,
+ const DataLayout &DL) {
// Skip over the first indices.
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1; i != Idx; ++i, ++GTI)
/*skip along*/;
-
+
// Compute the offset implied by the rest of the indices.
int64_t Offset = 0;
for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
- if (OpC == 0)
+ if (!OpC)
return VariableIdxFound = true;
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)) {
- Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
+ if (StructType *STy = dyn_cast<StructType>(*GTI)) {
+ Offset += DL.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
continue;
}
-
+
// Otherwise, we have a sequential type like an array or vector. Multiply
// the index by the ElementSize.
- uint64_t Size = TD.getTypePaddedSize(GTI.getIndexedType());
+ uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType());
Offset += Size*OpC->getSExtValue();
}
return Offset;
}
-/// IsPointerOffset - Return true if Ptr1 is provably equal to Ptr2 plus a
-/// 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.
+/// Return true if Ptr1 is provably equal to Ptr2 plus a 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 DataLayout &DL) {
+ Ptr1 = Ptr1->stripPointerCasts();
+ Ptr2 = Ptr2->stripPointerCasts();
+
+ // Handle the trivial case first.
+ if (Ptr1 == Ptr2) {
+ Offset = 0;
+ return true;
+ }
+
+ GEPOperator *GEP1 = dyn_cast<GEPOperator>(Ptr1);
+ GEPOperator *GEP2 = dyn_cast<GEPOperator>(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 && GEP1->getOperand(0)->stripPointerCasts() == Ptr2) {
+ Offset = -GetOffsetFromIndex(GEP1, 1, VariableIdxFound, DL);
+ return !VariableIdxFound;
+ }
+
+ if (GEP2 && !GEP1 && GEP2->getOperand(0)->stripPointerCasts() == Ptr1) {
+ Offset = GetOffsetFromIndex(GEP2, 1, VariableIdxFound, DL);
+ 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;
-
+
// Skip any common indices and track the GEP types.
unsigned Idx = 1;
for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx)
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);
+ int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, DL);
+ int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, DL);
if (VariableIdxFound) return false;
-
+
Offset = Offset2-Offset1;
return true;
}
-/// MemsetRange - Represents a range of memset'd bytes with the ByteVal value.
+/// Represents a range of memset'd bytes with the ByteVal value.
/// This allows us to analyze stores like:
/// store 0 -> P+1
/// store 0 -> P+0
namespace {
struct MemsetRange {
// Start/End - A semi range that describes the span that this range covers.
- // The range is closed at the start and open at the end: [Start, End).
+ // The range is closed at the start and open at the end: [Start, End).
int64_t Start, End;
/// StartPtr - The getelementptr instruction that points to the start of the
/// range.
Value *StartPtr;
-
+
/// Alignment - The known alignment of the first store.
unsigned Alignment;
-
+
/// TheStores - The actual stores that make up this range.
- SmallVector<StoreInst*, 16> TheStores;
-
- bool isProfitableToUseMemset(const TargetData &TD) const;
+ SmallVector<Instruction*, 16> TheStores;
+ bool isProfitableToUseMemset(const DataLayout &DL) 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;
-
+bool MemsetRange::isProfitableToUseMemset(const DataLayout &DL) const {
+ // 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 (Instruction *SI : TheStores)
+ if (!isa<StoreInst>(SI))
+ 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.
// However, merging 2 32-bit stores isn't useful on a 32-bit architecture (the
// pessimize the llvm optimizer.
//
// Since we don't have perfect knowledge here, make some assumptions: assume
- // the maximum GPR width is the same size as the pointer size and assume that
- // this width can be stored. If so, check to see whether we will end up
- // actually reducing the number of stores used.
+ // the maximum GPR width is the same size as the largest legal integer
+ // size. If so, check to see whether we will end up actually reducing the
+ // number of stores used.
unsigned Bytes = unsigned(End-Start);
- unsigned NumPointerStores = Bytes/TD.getPointerSize();
-
+ unsigned MaxIntSize = DL.getLargestLegalIntTypeSize();
+ if (MaxIntSize == 0)
+ MaxIntSize = 1;
+ unsigned NumPointerStores = Bytes / MaxIntSize;
+
// Assume the remaining bytes if any are done a byte at a time.
- unsigned NumByteStores = Bytes - NumPointerStores*TD.getPointerSize();
-
+ unsigned NumByteStores = Bytes % MaxIntSize;
+
// If we will reduce the # stores (according to this heuristic), do the
// transformation. This encourages merging 4 x i8 -> i32 and 2 x i16 -> i32
// etc.
return TheStores.size() > NumPointerStores+NumByteStores;
-}
+}
namespace {
class MemsetRanges {
- /// Ranges - A sorted list of the memset ranges. We use std::list here
- /// because each element is relatively large and expensive to copy.
- std::list<MemsetRange> Ranges;
- typedef std::list<MemsetRange>::iterator range_iterator;
- TargetData &TD;
+ /// A sorted list of the memset ranges.
+ SmallVector<MemsetRange, 8> Ranges;
+ typedef SmallVectorImpl<MemsetRange>::iterator range_iterator;
+ const DataLayout &DL;
public:
- MemsetRanges(TargetData &td) : TD(td) {}
-
- typedef std::list<MemsetRange>::const_iterator const_iterator;
+ MemsetRanges(const DataLayout &DL) : DL(DL) {}
+
+ typedef SmallVectorImpl<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 = DL.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
+/// 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.
- range_iterator I = Ranges.begin(), E = Ranges.end();
-
- while (I != E && Start > I->End)
- ++I;
-
+void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
+ unsigned Alignment, Instruction *Inst) {
+ int64_t End = Start+Size;
+
+ range_iterator I = std::lower_bound(Ranges.begin(), Ranges.end(), Start,
+ [](const MemsetRange &LHS, int64_t RHS) { return LHS.End < RHS; });
+
// We now know that I == E, in which case we didn't find anything to merge
// with, or that Start <= I->End. If End < I->Start or I == E, then we need
// to insert a new range. Handle this now.
- if (I == E || End < I->Start) {
+ if (I == Ranges.end() || End < I->Start) {
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.
if (I->Start <= Start && I->End >= End)
return;
-
+
// Now we know that Start <= I->End and End >= I->Start so the range overlaps
// but is not entirely contained within the range.
-
+
// See if the range extends the start of the range. In this case, it couldn't
// possibly cause it to join the prior range, because otherwise we would have
// stopped on *it*.
if (Start < I->Start) {
I->Start = Start;
- I->StartPtr = SI->getPointerOperand();
+ I->StartPtr = Ptr;
+ I->Alignment = Alignment;
}
-
+
// Now we know that Start <= I->End and Start >= I->Start (so the startpoint
// is in or right at the end of I), and that End >= I->Start. Extend I out to
// End.
if (End > I->End) {
I->End = End;
range_iterator NextI = I;
- while (++NextI != E && End >= NextI->Start) {
+ while (++NextI != Ranges.end() && End >= NextI->Start) {
// Merge the range in.
I->TheStores.append(NextI->TheStores.begin(), NextI->TheStores.end());
if (NextI->End > I->End)
//===----------------------------------------------------------------------===//
namespace {
-
- class VISIBILITY_HIDDEN MemCpyOpt : public FunctionPass {
- bool runOnFunction(Function &F);
+ class MemCpyOpt : public FunctionPass {
+ MemoryDependenceAnalysis *MD;
+ TargetLibraryInfo *TLI;
public:
static char ID; // Pass identification, replacement for typeid
- MemCpyOpt() : FunctionPass(&ID) {}
+ MemCpyOpt() : FunctionPass(ID) {
+ initializeMemCpyOptPass(*PassRegistry::getPassRegistry());
+ MD = nullptr;
+ TLI = nullptr;
+ }
+
+ bool runOnFunction(Function &F) override;
private:
// This transformation requires dominator postdominator info
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
- AU.addRequired<DominatorTree>();
+ AU.addRequired<AssumptionCacheTracker>();
+ AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<MemoryDependenceAnalysis>();
- AU.addRequired<AliasAnalysis>();
- AU.addRequired<TargetData>();
- AU.addPreserved<AliasAnalysis>();
+ AU.addRequired<AAResultsWrapperPass>();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
+ AU.addPreserved<GlobalsAAWrapperPass>();
AU.addPreserved<MemoryDependenceAnalysis>();
- AU.addPreserved<TargetData>();
}
-
- // Helper fuctions
- bool processStore(StoreInst *SI, BasicBlock::iterator& BBI);
- bool processMemCpy(MemCpyInst* M);
- bool performCallSlotOptzn(MemCpyInst* cpy, CallInst* C);
+
+ // Helper functions
+ bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
+ bool processMemSet(MemSetInst *SI, BasicBlock::iterator &BBI);
+ bool processMemCpy(MemCpyInst *M);
+ bool processMemMove(MemMoveInst *M);
+ bool performCallSlotOptzn(Instruction *cpy, Value *cpyDst, Value *cpySrc,
+ uint64_t cpyLen, unsigned cpyAlign, CallInst *C);
+ bool processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep);
+ bool processMemSetMemCpyDependence(MemCpyInst *M, MemSetInst *MDep);
+ bool performMemCpyToMemSetOptzn(MemCpyInst *M, MemSetInst *MDep);
+ bool processByValArgument(CallSite CS, unsigned ArgNo);
+ Instruction *tryMergingIntoMemset(Instruction *I, Value *StartPtr,
+ Value *ByteVal);
+
bool iterateOnFunction(Function &F);
};
-
+
char MemCpyOpt::ID = 0;
}
-// createMemCpyOptPass - The public interface to this file...
+/// The public interface to this file...
FunctionPass *llvm::createMemCpyOptPass() { return new MemCpyOpt(); }
-static RegisterPass<MemCpyOpt> X("memcpyopt",
- "MemCpy Optimization");
-
-
-
-/// processStore - When GVN is 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;
-
- // 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.
- Value *ByteVal = isBytewiseValue(SI->getOperand(0));
- if (!ByteVal)
- return false;
-
- TargetData &TD = getAnalysis<TargetData>();
- AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
+INITIALIZE_PASS_BEGIN(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
+ false, false)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
+INITIALIZE_PASS_END(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
+ false, false)
+
+/// 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 consecutive ones, it attempts to merge them
+/// together into a memcpy/memset.
+Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
+ Value *StartPtr, Value *ByteVal) {
+ const DataLayout &DL = StartInst->getModule()->getDataLayout();
// 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;
+ MemsetRanges Ranges(DL);
+
+ 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 (BI->mayWriteToMemory() || BI->mayReadFromMemory())
+ break;
+ continue;
+ }
- // If this is a non-store instruction it is fine, ignore it.
- StoreInst *NextStore = dyn_cast<StoreInst>(BI);
- if (NextStore == 0) continue;
-
- // If this is a store, see if we can merge it in.
- if (NextStore->isVolatile()) break;
-
- // Check to see if this stored value is of the same byte-splattable value.
- if (ByteVal != isBytewiseValue(NextStore->getOperand(0)))
- 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 store is to a constant offset from the start ptr.
- int64_t Offset;
- if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(), Offset, TD))
- 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,
+ DL))
+ break;
+
+ Ranges.addStore(Offset, NextStore);
+ } else {
+ MemSetInst *MSI = cast<MemSetInst>(BI);
- Ranges.addStore(Offset, NextStore);
+ 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, DL))
+ 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 nullptr;
+
// 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);
-
- Function *MemSetF = 0;
-
// 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;
- for (MemsetRanges::const_iterator I = Ranges.begin(), E = Ranges.end();
- I != E; ++I) {
- const MemsetRange &Range = *I;
+ Instruction *AMemSet = nullptr;
+ for (const MemsetRange &Range : Ranges) {
if (Range.TheStores.size() == 1) continue;
-
+
// If it is profitable to lower this range to memset, do so now.
- if (!Range.isProfitableToUseMemset(TD))
+ if (!Range.isProfitableToUseMemset(DL))
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;
-
- if (MemSetF == 0) {
- const Type *Tys[] = {Type::Int64Ty};
- MemSetF = Intrinsic::getDeclaration(SI->getParent()->getParent()
- ->getParent(), Intrinsic::memset,
- Tys, 1);
- }
-
+
+ // Otherwise, we do want to transform this! Create a new memset.
// Get the starting pointer of the block.
StartPtr = Range.StartPtr;
-
- // Cast the start ptr to be i8* as memset requires.
- const Type *i8Ptr = PointerType::getUnqual(Type::Int8Ty);
- if (StartPtr->getType() != i8Ptr)
- StartPtr = new BitCastInst(StartPtr, i8Ptr, StartPtr->getNameStart(),
- InsertPt);
-
- Value *Ops[] = {
- StartPtr, ByteVal, // Start, value
- ConstantInt::get(Type::Int64Ty, Range.End-Range.Start), // size
- ConstantInt::get(Type::Int32Ty, Range.Alignment) // align
- };
- Value *C = CallInst::Create(MemSetF, Ops, Ops+4, "", InsertPt);
- DEBUG(cerr << "Replace stores:\n";
- for (unsigned i = 0, e = Range.TheStores.size(); i != e; ++i)
- cerr << *Range.TheStores[i];
- cerr << "With: " << *C); C=C;
-
- // Don't invalidate the iterator
- BBI = BI;
-
+
+ // Determine alignment
+ unsigned Alignment = Range.Alignment;
+ if (Alignment == 0) {
+ Type *EltType =
+ cast<PointerType>(StartPtr->getType())->getElementType();
+ Alignment = DL.getABITypeAlignment(EltType);
+ }
+
+ AMemSet =
+ Builder.CreateMemSet(StartPtr, ByteVal, Range.End-Range.Start, Alignment);
+
+ DEBUG(dbgs() << "Replace stores:\n";
+ for (Instruction *SI : Range.TheStores)
+ dbgs() << *SI << '\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 SI = Range.TheStores.begin(),
- SE = Range.TheStores.end(); SI != SE; ++SI)
- (*SI)->eraseFromParent();
+ for (Instruction *SI : Range.TheStores) {
+ MD->removeInstruction(SI);
+ SI->eraseFromParent();
+ }
++NumMemSetInfer;
- MadeChange = true;
}
-
- return MadeChange;
+
+ return AMemSet;
}
+static unsigned findCommonAlignment(const DataLayout &DL, const StoreInst *SI,
+ const LoadInst *LI) {
+ unsigned StoreAlign = SI->getAlignment();
+ if (!StoreAlign)
+ StoreAlign = DL.getABITypeAlignment(SI->getOperand(0)->getType());
+ unsigned LoadAlign = LI->getAlignment();
+ if (!LoadAlign)
+ LoadAlign = DL.getABITypeAlignment(LI->getType());
+
+ return std::min(StoreAlign, LoadAlign);
+}
+
+bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
+ if (!SI->isSimple()) return false;
+
+ // Avoid merging nontemporal stores since the resulting
+ // memcpy/memset would not be able to preserve the nontemporal hint.
+ // In theory we could teach how to propagate the !nontemporal metadata to
+ // memset calls. However, that change would force the backend to
+ // conservatively expand !nontemporal memset calls back to sequences of
+ // store instructions (effectively undoing the merging).
+ if (SI->getMetadata(LLVMContext::MD_nontemporal))
+ return false;
+
+ const DataLayout &DL = SI->getModule()->getDataLayout();
+
+ // Load to store forwarding can be interpreted as memcpy.
+ if (LoadInst *LI = dyn_cast<LoadInst>(SI->getOperand(0))) {
+ if (LI->isSimple() && LI->hasOneUse() &&
+ LI->getParent() == SI->getParent()) {
+
+ auto *T = LI->getType();
+ if (T->isAggregateType()) {
+ AliasAnalysis &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
+ MemoryLocation LoadLoc = MemoryLocation::get(LI);
+
+ // We use alias analysis to check if an instruction may store to
+ // the memory we load from in between the load and the store. If
+ // such an instruction is found, we try to promote there instead
+ // of at the store position.
+ Instruction *P = SI;
+ for (BasicBlock::iterator I = ++LI->getIterator(), E = SI->getIterator();
+ I != E; ++I) {
+ if (!(AA.getModRefInfo(&*I, LoadLoc) & MRI_Mod))
+ continue;
+
+ // We found an instruction that may write to the loaded memory.
+ // We can try to promote at this position instead of the store
+ // position if nothing alias the store memory after this.
+ P = &*I;
+ for (; I != E; ++I) {
+ MemoryLocation StoreLoc = MemoryLocation::get(SI);
+ if (AA.getModRefInfo(&*I, StoreLoc) != MRI_NoModRef) {
+ P = nullptr;
+ break;
+ }
+ }
+
+ break;
+ }
+
+ // If a valid insertion position is found, then we can promote
+ // the load/store pair to a memcpy.
+ if (P) {
+ // If we load from memory that may alias the memory we store to,
+ // memmove must be used to preserve semantic. If not, memcpy can
+ // be used.
+ bool UseMemMove = false;
+ if (!AA.isNoAlias(MemoryLocation::get(SI), LoadLoc))
+ UseMemMove = true;
+
+ unsigned Align = findCommonAlignment(DL, SI, LI);
+ uint64_t Size = DL.getTypeStoreSize(T);
+
+ IRBuilder<> Builder(P);
+ Instruction *M;
+ if (UseMemMove)
+ M = Builder.CreateMemMove(SI->getPointerOperand(),
+ LI->getPointerOperand(), Size,
+ Align, SI->isVolatile());
+ else
+ M = Builder.CreateMemCpy(SI->getPointerOperand(),
+ LI->getPointerOperand(), Size,
+ Align, SI->isVolatile());
+
+ DEBUG(dbgs() << "Promoting " << *LI << " to " << *SI
+ << " => " << *M << "\n");
+
+ MD->removeInstruction(SI);
+ SI->eraseFromParent();
+ MD->removeInstruction(LI);
+ LI->eraseFromParent();
+ ++NumMemCpyInstr;
+
+ // Make sure we do not invalidate the iterator.
+ BBI = M->getIterator();
+ return true;
+ }
+ }
+
+ // 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.
+ MemDepResult ldep = MD->getDependency(LI);
+ CallInst *C = nullptr;
+ 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<AAResultsWrapperPass>().getAAResults();
+ MemoryLocation StoreLoc = MemoryLocation::get(SI);
+ for (BasicBlock::iterator I = --SI->getIterator(), E = C->getIterator();
+ I != E; --I) {
+ if (AA.getModRefInfo(&*I, StoreLoc) != MRI_NoModRef) {
+ C = nullptr;
+ break;
+ }
+ }
+ }
+
+ if (C) {
+ bool changed = performCallSlotOptzn(
+ LI, SI->getPointerOperand()->stripPointerCasts(),
+ LI->getPointerOperand()->stripPointerCasts(),
+ DL.getTypeStoreSize(SI->getOperand(0)->getType()),
+ findCommonAlignment(DL, SI, LI), 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.
-/// performCallSlotOptzn - takes a memcpy and a call that it depends on,
+ // 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->getIterator(); // 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->getIterator(); // Don't invalidate iterator.
+ return true;
+ }
+ return false;
+}
+
+
+/// 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, unsigned cpyAlign,
+ 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);
+ AllocaInst
*srcAlloca = dyn_cast<AllocaInst>(cpySrc);
if (!srcAlloca)
return false;
- // Check that all of src is copied to dest.
- TargetData& TD = getAnalysis<TargetData>();
-
- ConstantInt* srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
+ ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
if (!srcArraySize)
return false;
- uint64_t srcSize = TD.getTypePaddedSize(srcAlloca->getAllocatedType()) *
- srcArraySize->getZExtValue();
+ const DataLayout &DL = cpy->getModule()->getDataLayout();
+ uint64_t srcSize = DL.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
// trap. Otherwise the transform is invalid since it might cause a trap
// to occur earlier than it otherwise would.
- if (AllocaInst
* A = dyn_cast<AllocaInst>(cpyDest)) {
+ if (AllocaInst
*A = dyn_cast<AllocaInst>(cpyDest)) {
// The destination is an alloca. Check it is larger than srcSize.
- ConstantInt* destArraySize = dyn_cast<ConstantInt>(A->getArraySize());
+ ConstantInt *destArraySize = dyn_cast<ConstantInt>(A->getArraySize());
if (!destArraySize)
return false;
- uint64_t destSize = TD.getTypePaddedSize(A->getAllocatedType()) *
- destArraySize->getZExtValue();
+ uint64_t destSize = DL.getTypeAllocSize(A->getAllocatedType()) *
+ destArraySize->getZExtValue();
if (destSize < srcSize)
return false;
- } else if (Argument* A = dyn_cast<Argument>(cpyDest)) {
- // If the destination is an sret parameter then only accesses that are
- // outside of the returned struct type can trap.
- if (!A->hasStructRetAttr())
- return false;
+ } else if (Argument *A = dyn_cast<Argument>(cpyDest)) {
+ if (A->getDereferenceableBytes() < srcSize) {
+ // If the destination is an sret parameter then only accesses that are
+ // outside of the returned struct type can trap.
+ if (!A->hasStructRetAttr())
+ return false;
- const Type* StructTy = cast<PointerType>(A->getType())->getElementType();
- uint64_t destSize = TD.getTypePaddedSize(StructTy);
+ Type *StructTy = cast<PointerType>(A->getType())->getElementType();
+ if (!StructTy->isSized()) {
+ // The call may never return and hence the copy-instruction may never
+ // be executed, and therefore it's not safe to say "the destination
+ // has at least <cpyLen> bytes, as implied by the copy-instruction",
+ return false;
+ }
- if (destSize < srcSize)
- return false;
+ uint64_t destSize = DL.getTypeAllocSize(StructTy);
+ if (destSize < srcSize)
+ return false;
+ }
} else {
return false;
}
+ // Check that dest points to memory that is at least as aligned as src.
+ unsigned srcAlign = srcAlloca->getAlignment();
+ if (!srcAlign)
+ srcAlign = DL.getABITypeAlignment(srcAlloca->getAllocatedType());
+ bool isDestSufficientlyAligned = srcAlign <= cpyAlign;
+ // If dest is not aligned enough and we can't increase its alignment then
+ // bail out.
+ if (!isDestSufficientlyAligned && !isa<AllocaInst>(cpyDest))
+ return false;
+
// Check that src is not accessed except via the call and the memcpy. This
// guarantees that it holds only undefined values when passed in (so the final
// memcpy can be dropped), that it is not read or written between the call and
// the memcpy, and that writing beyond the end of it is undefined.
- SmallVector<User*, 8> srcUseList(srcAlloca->use_begin(),
- srcAlloca->use_end());
+ SmallVector<User*, 8> srcUseList(srcAlloca->user_begin(),
+ srcAlloca->user_end());
while (!srcUseList.empty()) {
- User* UI = srcUseList.back();
- srcUseList.pop_back();
-
- if (isa<BitCastInst>(UI)) {
- for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
- I != E; ++I)
- srcUseList.push_back(*I);
- } else if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(UI)) {
- if (G->hasAllZeroIndices())
- for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
- I != E; ++I)
- srcUseList.push_back(*I);
- else
+ User *U = srcUseList.pop_back_val();
+
+ if (isa<BitCastInst>(U) || isa<AddrSpaceCastInst>(U)) {
+ for (User *UU : U->users())
+ srcUseList.push_back(UU);
+ continue;
+ }
+ if (GetElementPtrInst *G = dyn_cast<GetElementPtrInst>(U)) {
+ if (!G->hasAllZeroIndices())
return false;
- } else if (UI != C && UI != cpy) {
- return false;
+
+ for (User *UU : U->users())
+ srcUseList.push_back(UU);
+ continue;
}
+ if (const IntrinsicInst *IT = dyn_cast<IntrinsicInst>(U))
+ if (IT->getIntrinsicID() == Intrinsic::lifetime_start ||
+ IT->getIntrinsicID() == Intrinsic::lifetime_end)
+ continue;
+
+ if (U != C && U != cpy)
+ return false;
}
+ // Check that src isn't captured by the called function since the
+ // transformation can cause aliasing issues in that case.
+ for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
+ if (CS.getArgument(i) == cpySrc && !CS.doesNotCapture(i))
+ return false;
+
// Since we're changing the parameter to the callsite, we need to make sure
// that what would be the new parameter dominates the callsite.
- DominatorTree& DT = getAnalysis<DominatorTree>();
- if (Instruction* cpyDestInst = dyn_cast<Instruction>(cpyDest))
+ DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ if (Instruction *cpyDestInst = dyn_cast<Instruction>(cpyDest))
if (!DT.dominates(cpyDestInst, C))
return false;
// unexpected manner, for example via a global, which we deduce from
// 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)
+ AliasAnalysis &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
+ ModRefInfo MR = AA.getModRefInfo(C, cpyDest, srcSize);
+ // If necessary, perform additional analysis.
+ if (MR != MRI_NoModRef)
+ MR = AA.callCapturesBefore(C, cpyDest, srcSize, &DT);
+ if (MR != MRI_NoModRef)
return false;
// All the checks have passed, so do the transformation.
bool changedArgument = false;
for (unsigned i = 0; i < CS.arg_size(); ++i)
if (CS.getArgument(i)->stripPointerCasts() == cpySrc) {
- if (cpySrc->getType() != cpyDest->getType())
- cpyDest = CastInst::CreatePointerCast(cpyDest, cpySrc->getType(),
- cpyDest->getName(), C);
+ Value *Dest = cpySrc->getType() == cpyDest->getType() ? cpyDest
+ : CastInst::CreatePointerCast(cpyDest, cpySrc->getType(),
+ cpyDest->getName(), C);
changedArgument = true;
- if (CS.getArgument(i)->getType() != cpyDest->getType())
- CS.setArgument(i, CastInst::CreatePointerCast(cpyDest,
- CS.getArgument(i)->getType(), cpyDest->getName(), C));
+ if (CS.getArgument(i)->getType() == Dest->getType())
+ CS.setArgument(i, Dest);
else
- CS.setArgument(i, cpyDest);
+ CS.setArgument(i, CastInst::CreatePointerCast(Dest,
+ CS.getArgument(i)->getType(), Dest->getName(), C));
}
if (!changedArgument)
return false;
+ // If the destination wasn't sufficiently aligned then increase its alignment.
+ if (!isDestSufficientlyAligned) {
+ assert(isa<AllocaInst>(cpyDest) && "Can only increase alloca alignment!");
+ cast<AllocaInst>(cpyDest)->setAlignment(srcAlign);
+ }
+
// 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);
+
+ // Update AA metadata
+ // FIXME: MD_tbaa_struct and MD_mem_parallel_loop_access should also be
+ // handled here, but combineMetadata doesn't support them yet
+ unsigned KnownIDs[] = {LLVMContext::MD_tbaa, LLVMContext::MD_alias_scope,
+ LLVMContext::MD_noalias,
+ LLVMContext::MD_invariant_group};
+ combineMetadata(C, cpy, KnownIDs);
- // Remove the memcpy
- MD.removeInstruction(cpy);
- cpy->eraseFromParent();
- NumMemCpyInstr++;
+ // 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());
-
+/// 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.
+bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep) {
// 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;
+
+ // 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;
-
- // Second, the length of the memcpy's must be the same, or the preceeding one
+
+ // Second, the length of the memcpy's must be the same, or the preceding 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)
+ ConstantInt *MDepLen = dyn_cast<ConstantInt>(MDep->getLength());
+ ConstantInt *MLen = dyn_cast<ConstantInt>(M->getLength());
+ if (!MDepLen || !MLen || MDepLen->getZExtValue() < MLen->getZExtValue())
return false;
-
- uint64_t DepSize = C1->getValue().getZExtValue();
- uint64_t CpySize = C2->getValue().getZExtValue();
-
- if (DepSize < CpySize)
+
+ AliasAnalysis &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
+
+ // 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(MemoryLocation::getForSource(MDep), false,
+ M->getIterator(), M->getParent());
+ if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
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)
+
+ // 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(MemoryLocation::getForDest(M),
+ MemoryLocation::getForSource(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;
+}
+
+/// We've found that the (upward scanning) memory dependence of \p MemCpy is
+/// \p MemSet. Try to simplify \p MemSet to only set the trailing bytes that
+/// weren't copied over by \p MemCpy.
+///
+/// In other words, transform:
+/// \code
+/// memset(dst, c, dst_size);
+/// memcpy(dst, src, src_size);
+/// \endcode
+/// into:
+/// \code
+/// memcpy(dst, src, src_size);
+/// memset(dst + src_size, c, dst_size <= src_size ? 0 : dst_size - src_size);
+/// \endcode
+bool MemCpyOpt::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
+ MemSetInst *MemSet) {
+ // We can only transform memset/memcpy with the same destination.
+ if (MemSet->getDest() != MemCpy->getDest())
+ return false;
+
+ // Check that there are no other dependencies on the memset destination.
+ MemDepResult DstDepInfo =
+ MD->getPointerDependencyFrom(MemoryLocation::getForDest(MemSet), false,
+ MemCpy->getIterator(), MemCpy->getParent());
+ if (DstDepInfo.getInst() != MemSet)
return false;
- else if (AA.alias(M->getRawDest(), CpySize, M->getRawSource(), CpySize) !=
- AliasAnalysis::NoAlias)
+
+ // Use the same i8* dest as the memcpy, killing the memset dest if different.
+ Value *Dest = MemCpy->getRawDest();
+ Value *DestSize = MemSet->getLength();
+ Value *SrcSize = MemCpy->getLength();
+
+ // By default, create an unaligned memset.
+ unsigned Align = 1;
+ // If Dest is aligned, and SrcSize is constant, use the minimum alignment
+ // of the sum.
+ const unsigned DestAlign =
+ std::max(MemSet->getAlignment(), MemCpy->getAlignment());
+ if (DestAlign > 1)
+ if (ConstantInt *SrcSizeC = dyn_cast<ConstantInt>(SrcSize))
+ Align = MinAlign(SrcSizeC->getZExtValue(), DestAlign);
+
+ IRBuilder<> Builder(MemCpy);
+
+ // If the sizes have different types, zext the smaller one.
+ if (DestSize->getType() != SrcSize->getType()) {
+ if (DestSize->getType()->getIntegerBitWidth() >
+ SrcSize->getType()->getIntegerBitWidth())
+ SrcSize = Builder.CreateZExt(SrcSize, DestSize->getType());
+ else
+ DestSize = Builder.CreateZExt(DestSize, SrcSize->getType());
+ }
+
+ Value *MemsetLen =
+ Builder.CreateSelect(Builder.CreateICmpULE(DestSize, SrcSize),
+ ConstantInt::getNullValue(DestSize->getType()),
+ Builder.CreateSub(DestSize, SrcSize));
+ Builder.CreateMemSet(Builder.CreateGEP(Dest, SrcSize), MemSet->getOperand(1),
+ MemsetLen, Align);
+
+ MD->removeInstruction(MemSet);
+ MemSet->eraseFromParent();
+ return true;
+}
+
+/// Transform memcpy to memset when its source was just memset.
+/// In other words, turn:
+/// \code
+/// memset(dst1, c, dst1_size);
+/// memcpy(dst2, dst1, dst2_size);
+/// \endcode
+/// into:
+/// \code
+/// memset(dst1, c, dst1_size);
+/// memset(dst2, c, dst2_size);
+/// \endcode
+/// When dst2_size <= dst1_size.
+///
+/// The \p MemCpy must have a Constant length.
+bool MemCpyOpt::performMemCpyToMemSetOptzn(MemCpyInst *MemCpy,
+ MemSetInst *MemSet) {
+ // This only makes sense on memcpy(..., memset(...), ...).
+ if (MemSet->getRawDest() != MemCpy->getRawSource())
return false;
- else if (AA.alias(MDep->getRawDest(), DepSize, MDep->getRawSource(), DepSize)
- != AliasAnalysis::NoAlias)
+
+ ConstantInt *CopySize = cast<ConstantInt>(MemCpy->getLength());
+ ConstantInt *MemSetSize = dyn_cast<ConstantInt>(MemSet->getLength());
+ // Make sure the memcpy doesn't read any more than what the memset wrote.
+ // Don't worry about sizes larger than i64.
+ if (!MemSetSize || CopySize->getZExtValue() > MemSetSize->getZExtValue())
return false;
-
- // If all checks passed, then we can transform these memcpy's
- const Type *Tys[1];
- Tys[0] = M->getLength()->getType();
- Function* MemCpyFun = Intrinsic::getDeclaration(
- M->getParent()->getParent()->getParent(),
- M->getIntrinsicID(), Tys, 1);
-
- Value *Args[4] = {
- M->getRawDest(), MDep->getRawSource(), M->getLength(), M->getAlignmentCst()
- };
-
- CallInst* C = CallInst::Create(MemCpyFun, Args, Args+4, "", 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);
+
+ IRBuilder<> Builder(MemCpy);
+ Builder.CreateMemSet(MemCpy->getRawDest(), MemSet->getOperand(1),
+ CopySize, MemCpy->getAlignment());
+ return true;
+}
+
+/// 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 non-volatile memcpy's.
+ if (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, M->getLength(),
+ M->getAlignment(), false);
+ MD->removeInstruction(M);
+ M->eraseFromParent();
+ ++NumCpyToSet;
+ return true;
+ }
+
+ MemDepResult DepInfo = MD->getDependency(M);
+
+ // Try to turn a partially redundant memset + memcpy into
+ // memcpy + smaller memset. We don't need the memcpy size for this.
+ if (DepInfo.isClobber())
+ if (MemSetInst *MDep = dyn_cast<MemSetInst>(DepInfo.getInst()))
+ if (processMemSetMemCpyDependence(M, MDep))
+ return true;
+
+ // The optimizations after this point require the memcpy size.
+ ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
+ if (!CopySize) return false;
+
+ // There are four possible optimizations we can do for memcpy:
+ // a) memcpy-memcpy xform which exposes redundance for DSE.
+ // b) call-memcpy xform for return slot optimization.
+ // c) memcpy from freshly alloca'd space or space that has just started its
+ // lifetime copies undefined data, and we can therefore eliminate the
+ // memcpy in favor of the data that was already at the destination.
+ // d) memcpy from a just-memset'd source can be turned into memset.
+ if (DepInfo.isClobber()) {
+ if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
+ if (performCallSlotOptzn(M, M->getDest(), M->getSource(),
+ CopySize->getZExtValue(), M->getAlignment(),
+ C)) {
+ MD->removeInstruction(M);
+ M->eraseFromParent();
+ return true;
+ }
+ }
+ }
+
+ MemoryLocation SrcLoc = MemoryLocation::getForSource(M);
+ MemDepResult SrcDepInfo = MD->getPointerDependencyFrom(
+ SrcLoc, true, M->getIterator(), M->getParent());
+
+ if (SrcDepInfo.isClobber()) {
+ if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst()))
+ return processMemCpyMemCpyDependence(M, MDep);
+ } else if (SrcDepInfo.isDef()) {
+ Instruction *I = SrcDepInfo.getInst();
+ bool hasUndefContents = false;
+
+ if (isa<AllocaInst>(I)) {
+ hasUndefContents = true;
+ } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
+ if (II->getIntrinsicID() == Intrinsic::lifetime_start)
+ if (ConstantInt *LTSize = dyn_cast<ConstantInt>(II->getArgOperand(0)))
+ if (LTSize->getZExtValue() >= CopySize->getZExtValue())
+ hasUndefContents = true;
+ }
+
+ if (hasUndefContents) {
+ MD->removeInstruction(M);
+ M->eraseFromParent();
+ ++NumMemCpyInstr;
+ return true;
+ }
+ }
+
+ if (SrcDepInfo.isClobber())
+ if (MemSetInst *MDep = dyn_cast<MemSetInst>(SrcDepInfo.getInst()))
+ if (performMemCpyToMemSetOptzn(M, MDep)) {
+ MD->removeInstruction(M);
+ M->eraseFromParent();
+ ++NumCpyToSet;
+ return true;
+ }
+
return false;
}
-// MemCpyOpt::runOnFunction - This is the main transformation entry point for a
-// function.
-//
-bool MemCpyOpt::runOnFunction(Function& F) {
-
- bool changed = false;
- bool shouldContinue = true;
-
- while (shouldContinue) {
- shouldContinue = iterateOnFunction(F);
- changed |= shouldContinue;
- }
-
- return changed;
+/// Transforms memmove calls to memcpy calls when the src/dst are guaranteed
+/// not to alias.
+bool MemCpyOpt::processMemMove(MemMoveInst *M) {
+ AliasAnalysis &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
+
+ if (!TLI->has(LibFunc::memmove))
+ return false;
+
+ // See if the pointers alias.
+ if (!AA.isNoAlias(MemoryLocation::getForDest(M),
+ MemoryLocation::getForSource(M)))
+ return false;
+
+ DEBUG(dbgs() << "MemCpyOpt: Optimizing memmove -> memcpy: " << *M << "\n");
+
+ // If not, then we know we can transform this.
+ Type *ArgTys[3] = { M->getRawDest()->getType(),
+ M->getRawSource()->getType(),
+ M->getLength()->getType() };
+ M->setCalledFunction(Intrinsic::getDeclaration(M->getModule(),
+ Intrinsic::memcpy, ArgTys));
+
+ // MemDep may have over conservative information about this instruction, just
+ // conservatively flush it from the cache.
+ MD->removeInstruction(M);
+
+ ++NumMoveToCpy;
+ return true;
}
+/// This is called on every byval argument in call sites.
+bool MemCpyOpt::processByValArgument(CallSite CS, unsigned ArgNo) {
+ const DataLayout &DL = CS.getCaller()->getParent()->getDataLayout();
+ // Find out what feeds this byval argument.
+ Value *ByValArg = CS.getArgument(ArgNo);
+ Type *ByValTy = cast<PointerType>(ByValArg->getType())->getElementType();
+ uint64_t ByValSize = DL.getTypeAllocSize(ByValTy);
+ MemDepResult DepInfo = MD->getPointerDependencyFrom(
+ MemoryLocation(ByValArg, ByValSize), true,
+ CS.getInstruction()->getIterator(), 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 || 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 || 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.
+ AssumptionCache &AC =
+ getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
+ *CS->getParent()->getParent());
+ DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ if (MDep->getAlignment() < ByValAlign &&
+ getOrEnforceKnownAlignment(MDep->getSource(), ByValAlign, DL,
+ CS.getInstruction(), &AC, &DT) < 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(
+ MemoryLocation::getForSource(MDep), false,
+ CS.getInstruction()->getIterator(), 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());
-// MemCpyOpt::iterateOnFunction - Executes one iteration of GVN
+ 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;
+}
+
+/// Executes one iteration of MemCpyOpt.
bool MemCpyOpt::iterateOnFunction(Function &F) {
- bool changed_function = false;
+ bool MadeChange = false;
- // Walk all instruction in the function
+ // 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;) {
- // Avoid invalidating the iterator
- Instruction* I = BI++;
-
+ 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))
- changed_function |= processStore(SI, BI);
- else if (MemCpyInst* M = dyn_cast<MemCpyInst>(I)) {
- changed_function |= processMemCpy(M);
+ MadeChange |= processStore(SI, BI);
+ else if (MemSetInst *M = dyn_cast<MemSetInst>(I))
+ RepeatInstruction = processMemSet(M, BI);
+ else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I))
+ RepeatInstruction = processMemCpy(M);
+ else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I))
+ RepeatInstruction = processMemMove(M);
+ else if (auto CS = CallSite(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;
}
}
}
-
- return changed_function;
+
+ return MadeChange;
+}
+
+/// This is the main transformation entry point for a function.
+bool MemCpyOpt::runOnFunction(Function &F) {
+ if (skipOptnoneFunction(F))
+ return false;
+
+ bool MadeChange = false;
+ MD = &getAnalysis<MemoryDependenceAnalysis>();
+ TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+
+ // 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 = nullptr;
+ return MadeChange;
}
projects / oota-llvm.git / blobdiff