#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Function.h"
+#include "llvm/LLVMContext.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/PHITransAddr.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/PredIteratorCache.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Target/TargetData.h"
using namespace llvm;
STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses");
STATISTIC(NumCacheCompleteNonLocalPtr,
"Number of block queries that were completely cached");
+// Limit for the number of instructions to scan in a block.
+// FIXME: Figure out what a sane value is for this.
+// (500 is relatively insane.)
+static const int BlockScanLimit = 500;
+
char MemoryDependenceAnalysis::ID = 0;
// Register this pass...
-static RegisterPass<MemoryDependenceAnalysis> X("memdep",
- "Memory Dependence Analysis", false, true);
+INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep",
+ "Memory Dependence Analysis", false, true)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep",
+ "Memory Dependence Analysis", false, true)
MemoryDependenceAnalysis::MemoryDependenceAnalysis()
-: FunctionPass(&ID), PredCache(0) {
+: FunctionPass(ID), PredCache(0) {
+ initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry());
}
MemoryDependenceAnalysis::~MemoryDependenceAnalysis() {
}
bool MemoryDependenceAnalysis::runOnFunction(Function &) {
AA = &getAnalysis<AliasAnalysis>();
+ TD = getAnalysisIfAvailable<TargetData>();
+ DT = getAnalysisIfAvailable<DominatorTree>();
if (PredCache == 0)
PredCache.reset(new PredIteratorCache());
return false;
InstIt = ReverseMap.find(Inst);
assert(InstIt != ReverseMap.end() && "Reverse map out of sync?");
bool Found = InstIt->second.erase(Val);
- assert(Found && "Invalid reverse map!"); Found=Found;
+ assert(Found && "Invalid reverse map!"); (void)Found;
if (InstIt->second.empty())
ReverseMap.erase(InstIt);
}
+/// GetLocation - If the given instruction references a specific memory
+/// location, fill in Loc with the details, otherwise set Loc.Ptr to null.
+/// Return a ModRefInfo value describing the general behavior of the
+/// instruction.
+static
+AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst,
+ AliasAnalysis::Location &Loc,
+ AliasAnalysis *AA) {
+ if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
+ if (LI->isUnordered()) {
+ Loc = AA->getLocation(LI);
+ return AliasAnalysis::Ref;
+ } else if (LI->getOrdering() == Monotonic) {
+ Loc = AA->getLocation(LI);
+ return AliasAnalysis::ModRef;
+ }
+ Loc = AliasAnalysis::Location();
+ return AliasAnalysis::ModRef;
+ }
+
+ if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ if (SI->isUnordered()) {
+ Loc = AA->getLocation(SI);
+ return AliasAnalysis::Mod;
+ } else if (SI->getOrdering() == Monotonic) {
+ Loc = AA->getLocation(SI);
+ return AliasAnalysis::ModRef;
+ }
+ Loc = AliasAnalysis::Location();
+ return AliasAnalysis::ModRef;
+ }
+
+ if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
+ Loc = AA->getLocation(V);
+ return AliasAnalysis::ModRef;
+ }
+
+ if (const CallInst *CI = isFreeCall(Inst, AA->getTargetLibraryInfo())) {
+ // calls to free() deallocate the entire structure
+ Loc = AliasAnalysis::Location(CI->getArgOperand(0));
+ return AliasAnalysis::Mod;
+ }
+
+ if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
+ switch (II->getIntrinsicID()) {
+ case Intrinsic::lifetime_start:
+ case Intrinsic::lifetime_end:
+ case Intrinsic::invariant_start:
+ Loc = AliasAnalysis::Location(II->getArgOperand(1),
+ cast<ConstantInt>(II->getArgOperand(0))
+ ->getZExtValue(),
+ II->getMetadata(LLVMContext::MD_tbaa));
+ // These intrinsics don't really modify the memory, but returning Mod
+ // will allow them to be handled conservatively.
+ return AliasAnalysis::Mod;
+ case Intrinsic::invariant_end:
+ Loc = AliasAnalysis::Location(II->getArgOperand(2),
+ cast<ConstantInt>(II->getArgOperand(1))
+ ->getZExtValue(),
+ II->getMetadata(LLVMContext::MD_tbaa));
+ // These intrinsics don't really modify the memory, but returning Mod
+ // will allow them to be handled conservatively.
+ return AliasAnalysis::Mod;
+ default:
+ break;
+ }
+
+ // Otherwise, just do the coarse-grained thing that always works.
+ if (Inst->mayWriteToMemory())
+ return AliasAnalysis::ModRef;
+ if (Inst->mayReadFromMemory())
+ return AliasAnalysis::Ref;
+ return AliasAnalysis::NoModRef;
+}
/// getCallSiteDependencyFrom - Private helper for finding the local
/// dependencies of a call site.
MemDepResult MemoryDependenceAnalysis::
getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
BasicBlock::iterator ScanIt, BasicBlock *BB) {
+ unsigned Limit = BlockScanLimit;
+
// Walk backwards through the block, looking for dependencies
while (ScanIt != BB->begin()) {
+ // Limit the amount of scanning we do so we don't end up with quadratic
+ // running time on extreme testcases.
+ --Limit;
+ if (!Limit)
+ return MemDepResult::getUnknown();
+
Instruction *Inst = --ScanIt;
// If this inst is a memory op, get the pointer it accessed
- Value *Pointer = 0;
- uint64_t PointerSize = 0;
- if (StoreInst *S = dyn_cast<StoreInst>(Inst)) {
- Pointer = S->getPointerOperand();
- PointerSize = AA->getTypeStoreSize(S->getOperand(0)->getType());
- } else if (VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
- Pointer = V->getOperand(0);
- PointerSize = AA->getTypeStoreSize(V->getType());
- } else if (isFreeCall(Inst)) {
- Pointer = Inst->getOperand(1);
- // calls to free() erase the entire structure
- PointerSize = ~0ULL;
- } else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
+ AliasAnalysis::Location Loc;
+ AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA);
+ if (Loc.Ptr) {
+ // A simple instruction.
+ if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef)
+ return MemDepResult::getClobber(Inst);
+ continue;
+ }
+
+ if (CallSite InstCS = cast<Value>(Inst)) {
// Debug intrinsics don't cause dependences.
if (isa<DbgInfoIntrinsic>(Inst)) continue;
- CallSite InstCS = CallSite::get(Inst);
// If these two calls do not interfere, look past it.
switch (AA->getModRefInfo(CS, InstCS)) {
case AliasAnalysis::NoModRef:
- // If the two calls don't interact (e.g. InstCS is readnone) keep
- // scanning.
+ // If the two calls are the same, return InstCS as a Def, so that
+ // CS can be found redundant and eliminated.
+ if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) &&
+ CS.getInstruction()->isIdenticalToWhenDefined(Inst))
+ return MemDepResult::getDef(Inst);
+
+ // Otherwise if the two calls don't interact (e.g. InstCS is readnone)
+ // keep scanning.
continue;
- case AliasAnalysis::Ref:
- // If the two calls read the same memory locations and CS is a readonly
- // function, then we have two cases: 1) the calls may not interfere with
- // each other at all. 2) the calls may produce the same value. In case
- // #1 we want to ignore the values, in case #2, we want to return Inst
- // as a Def dependence. This allows us to CSE in cases like:
- // X = strlen(P);
- // memchr(...);
- // Y = strlen(P); // Y = X
- if (isReadOnlyCall) {
- if (CS.getCalledFunction() != 0 &&
- CS.getCalledFunction() == InstCS.getCalledFunction())
- return MemDepResult::getDef(Inst);
- // Ignore unrelated read/read call dependences.
- continue;
- }
- // FALL THROUGH
default:
return MemDepResult::getClobber(Inst);
}
- } else {
- // Non-memory instruction.
- continue;
}
-
- if (AA->getModRefInfo(CS, Pointer, PointerSize) != AliasAnalysis::NoModRef)
+
+ // If we could not obtain a pointer for the instruction and the instruction
+ // touches memory then assume that this is a dependency.
+ if (MR != AliasAnalysis::NoModRef)
return MemDepResult::getClobber(Inst);
}
-
- // No dependence found. If this is the entry block of the function, it is a
- // clobber, otherwise it is non-local.
+
+ // No dependence found. If this is the entry block of the function, it is
+ // unknown, otherwise it is non-local.
if (BB != &BB->getParent()->getEntryBlock())
return MemDepResult::getNonLocal();
- return MemDepResult::getClobber(ScanIt);
+ return MemDepResult::getNonFuncLocal();
+}
+
+/// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
+/// would fully overlap MemLoc if done as a wider legal integer load.
+///
+/// MemLocBase, MemLocOffset are lazily computed here the first time the
+/// base/offs of memloc is needed.
+static bool
+isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
+ const Value *&MemLocBase,
+ int64_t &MemLocOffs,
+ const LoadInst *LI,
+ const TargetData *TD) {
+ // If we have no target data, we can't do this.
+ if (TD == 0) return false;
+
+ // If we haven't already computed the base/offset of MemLoc, do so now.
+ if (MemLocBase == 0)
+ MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, *TD);
+
+ unsigned Size = MemoryDependenceAnalysis::
+ getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
+ LI, *TD);
+ return Size != 0;
+}
+
+/// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
+/// looks at a memory location for a load (specified by MemLocBase, Offs,
+/// and Size) and compares it against a load. If the specified load could
+/// be safely widened to a larger integer load that is 1) still efficient,
+/// 2) safe for the target, and 3) would provide the specified memory
+/// location value, then this function returns the size in bytes of the
+/// load width to use. If not, this returns zero.
+unsigned MemoryDependenceAnalysis::
+getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
+ unsigned MemLocSize, const LoadInst *LI,
+ const TargetData &TD) {
+ // We can only extend simple integer loads.
+ if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
+
+ // Get the base of this load.
+ int64_t LIOffs = 0;
+ const Value *LIBase =
+ GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, TD);
+
+ // If the two pointers are not based on the same pointer, we can't tell that
+ // they are related.
+ if (LIBase != MemLocBase) return 0;
+
+ // Okay, the two values are based on the same pointer, but returned as
+ // no-alias. This happens when we have things like two byte loads at "P+1"
+ // and "P+3". Check to see if increasing the size of the "LI" load up to its
+ // alignment (or the largest native integer type) will allow us to load all
+ // the bits required by MemLoc.
+
+ // If MemLoc is before LI, then no widening of LI will help us out.
+ if (MemLocOffs < LIOffs) return 0;
+
+ // Get the alignment of the load in bytes. We assume that it is safe to load
+ // any legal integer up to this size without a problem. For example, if we're
+ // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can
+ // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it
+ // to i16.
+ unsigned LoadAlign = LI->getAlignment();
+
+ int64_t MemLocEnd = MemLocOffs+MemLocSize;
+
+ // If no amount of rounding up will let MemLoc fit into LI, then bail out.
+ if (LIOffs+LoadAlign < MemLocEnd) return 0;
+
+ // This is the size of the load to try. Start with the next larger power of
+ // two.
+ unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U;
+ NewLoadByteSize = NextPowerOf2(NewLoadByteSize);
+
+ while (1) {
+ // If this load size is bigger than our known alignment or would not fit
+ // into a native integer register, then we fail.
+ if (NewLoadByteSize > LoadAlign ||
+ !TD.fitsInLegalInteger(NewLoadByteSize*8))
+ return 0;
+
+ if (LIOffs+NewLoadByteSize > MemLocEnd &&
+ LI->getParent()->getParent()->hasFnAttr(Attribute::AddressSafety)) {
+ // We will be reading past the location accessed by the original program.
+ // While this is safe in a regular build, Address Safety analysis tools
+ // may start reporting false warnings. So, don't do widening.
+ return 0;
+ }
+
+ // If a load of this width would include all of MemLoc, then we succeed.
+ if (LIOffs+NewLoadByteSize >= MemLocEnd)
+ return NewLoadByteSize;
+
+ NewLoadByteSize <<= 1;
+ }
}
/// getPointerDependencyFrom - Return the instruction on which a memory
-/// location depends. If isLoad is true, this routine ignore may-aliases with
-/// read-only operations.
+/// location depends. If isLoad is true, this routine ignores may-aliases with
+/// read-only operations. If isLoad is false, this routine ignores may-aliases
+/// with reads from read-only locations.
MemDepResult MemoryDependenceAnalysis::
-getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
+getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
BasicBlock::iterator ScanIt, BasicBlock *BB) {
- Value *InvariantTag = 0;
+ const Value *MemLocBase = 0;
+ int64_t MemLocOffset = 0;
+
+ unsigned Limit = BlockScanLimit;
// Walk backwards through the basic block, looking for dependencies.
while (ScanIt != BB->begin()) {
+ // Limit the amount of scanning we do so we don't end up with quadratic
+ // running time on extreme testcases.
+ --Limit;
+ if (!Limit)
+ return MemDepResult::getUnknown();
+
Instruction *Inst = --ScanIt;
- // If we're in an invariant region, no dependencies can be found before
- // we pass an invariant-begin marker.
- if (InvariantTag == Inst) {
- InvariantTag = 0;
- continue;
- }
-
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
- // Debug intrinsics don't cause dependences.
- if (isa<DbgInfoIntrinsic>(Inst)) continue;
-
- // If we pass an invariant-end marker, then we've just entered an
- // invariant region and can start ignoring dependencies.
- if (II->getIntrinsicID() == Intrinsic::invariant_end) {
- // FIXME: This only considers queries directly on the invariant-tagged
- // pointer, not on query pointers that are indexed off of them. It'd
- // be nice to handle that at some point.
- AliasAnalysis::AliasResult R =
- AA->alias(II->getOperand(3), ~0U, MemPtr, ~0U);
- if (R == AliasAnalysis::MustAlias) {
- InvariantTag = II->getOperand(1);
- continue;
- }
+ // Debug intrinsics don't (and can't) cause dependences.
+ if (isa<DbgInfoIntrinsic>(II)) continue;
// If we reach a lifetime begin or end marker, then the query ends here
// because the value is undefined.
- } else if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
+ if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
// FIXME: This only considers queries directly on the invariant-tagged
// pointer, not on query pointers that are indexed off of them. It'd
- // be nice to handle that at some point.
- AliasAnalysis::AliasResult R =
- AA->alias(II->getOperand(2), ~0U, MemPtr, ~0U);
- if (R == AliasAnalysis::MustAlias)
+ // be nice to handle that at some point (the right approach is to use
+ // GetPointerBaseWithConstantOffset).
+ if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)),
+ MemLoc))
return MemDepResult::getDef(II);
+ continue;
}
}
- // If we're querying on a load and we're in an invariant region, we're done
- // at this point. Nothing a load depends on can live in an invariant region.
- if (isLoad && InvariantTag) continue;
-
// Values depend on loads if the pointers are must aliased. This means that
// a load depends on another must aliased load from the same value.
if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
- Value *Pointer = LI->getPointerOperand();
- uint64_t PointerSize = AA->getTypeStoreSize(LI->getType());
+ // Atomic loads have complications involved.
+ // FIXME: This is overly conservative.
+ if (!LI->isUnordered())
+ return MemDepResult::getClobber(LI);
+
+ AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
// If we found a pointer, check if it could be the same as our pointer.
- AliasAnalysis::AliasResult R =
- AA->alias(Pointer, PointerSize, MemPtr, MemSize);
+ AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc);
+
+ if (isLoad) {
+ if (R == AliasAnalysis::NoAlias) {
+ // If this is an over-aligned integer load (for example,
+ // "load i8* %P, align 4") see if it would obviously overlap with the
+ // queried location if widened to a larger load (e.g. if the queried
+ // location is 1 byte at P+1). If so, return it as a load/load
+ // clobber result, allowing the client to decide to widen the load if
+ // it wants to.
+ if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
+ if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
+ isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
+ MemLocOffset, LI, TD))
+ return MemDepResult::getClobber(Inst);
+
+ continue;
+ }
+
+ // Must aliased loads are defs of each other.
+ if (R == AliasAnalysis::MustAlias)
+ return MemDepResult::getDef(Inst);
+
+#if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
+ // in terms of clobbering loads, but since it does this by looking
+ // at the clobbering load directly, it doesn't know about any
+ // phi translation that may have happened along the way.
+
+ // If we have a partial alias, then return this as a clobber for the
+ // client to handle.
+ if (R == AliasAnalysis::PartialAlias)
+ return MemDepResult::getClobber(Inst);
+#endif
+
+ // Random may-alias loads don't depend on each other without a
+ // dependence.
+ continue;
+ }
+
+ // Stores don't depend on other no-aliased accesses.
if (R == AliasAnalysis::NoAlias)
continue;
-
- // May-alias loads don't depend on each other without a dependence.
- if (isLoad && R == AliasAnalysis::MayAlias)
+
+ // Stores don't alias loads from read-only memory.
+ if (AA->pointsToConstantMemory(LoadLoc))
continue;
- // Stores depend on may and must aliased loads, loads depend on must-alias
- // loads.
+
+ // Stores depend on may/must aliased loads.
return MemDepResult::getDef(Inst);
}
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- // There can't be stores to the value we care about inside an
- // invariant region.
- if (InvariantTag) continue;
-
+ // Atomic stores have complications involved.
+ // FIXME: This is overly conservative.
+ if (!SI->isUnordered())
+ return MemDepResult::getClobber(SI);
+
// If alias analysis can tell that this store is guaranteed to not modify
// the query pointer, ignore it. Use getModRefInfo to handle cases where
// the query pointer points to constant memory etc.
- if (AA->getModRefInfo(SI, MemPtr, MemSize) == AliasAnalysis::NoModRef)
+ if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef)
continue;
// Ok, this store might clobber the query pointer. Check to see if it is
// a must alias: in this case, we want to return this as a def.
- Value *Pointer = SI->getPointerOperand();
- uint64_t PointerSize = AA->getTypeStoreSize(SI->getOperand(0)->getType());
+ AliasAnalysis::Location StoreLoc = AA->getLocation(SI);
// If we found a pointer, check if it could be the same as our pointer.
- AliasAnalysis::AliasResult R =
- AA->alias(Pointer, PointerSize, MemPtr, MemSize);
+ AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc);
if (R == AliasAnalysis::NoAlias)
continue;
- if (R == AliasAnalysis::MayAlias)
- return MemDepResult::getClobber(Inst);
- return MemDepResult::getDef(Inst);
+ if (R == AliasAnalysis::MustAlias)
+ return MemDepResult::getDef(Inst);
+ return MemDepResult::getClobber(Inst);
}
// If this is an allocation, and if we know that the accessed pointer is to
// a subsequent bitcast of the malloc call result. There can be stores to
// the malloced memory between the malloc call and its bitcast uses, and we
// need to continue scanning until the malloc call.
- if (isa<AllocaInst>(Inst) ||
- (isa<CallInst>(Inst) && extractMallocCall(Inst))) {
- Value *AccessPtr = MemPtr->getUnderlyingObject();
+ if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, AA->getTargetLibraryInfo())){
+ const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD);
- if (AccessPtr == Inst ||
- AA->alias(Inst, 1, AccessPtr, 1) == AliasAnalysis::MustAlias)
+ if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
return MemDepResult::getDef(Inst);
continue;
}
// See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
- switch (AA->getModRefInfo(Inst, MemPtr, MemSize)) {
+ AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
+ // If necessary, perform additional analysis.
+ if (MR == AliasAnalysis::ModRef)
+ MR = AA->callCapturesBefore(Inst, MemLoc, DT);
+ switch (MR) {
case AliasAnalysis::NoModRef:
// If the call has no effect on the queried pointer, just ignore it.
continue;
case AliasAnalysis::Mod:
- // If we're in an invariant region, we can ignore calls that ONLY
- // modify the pointer.
- if (InvariantTag) continue;
return MemDepResult::getClobber(Inst);
case AliasAnalysis::Ref:
// If the call is known to never store to the pointer, and if this is a
}
}
- // No dependence found. If this is the entry block of the function, it is a
- // clobber, otherwise it is non-local.
+ // No dependence found. If this is the entry block of the function, it is
+ // unknown, otherwise it is non-local.
if (BB != &BB->getParent()->getEntryBlock())
return MemDepResult::getNonLocal();
- return MemDepResult::getClobber(ScanIt);
+ return MemDepResult::getNonFuncLocal();
}
/// getDependency - Return the instruction on which a memory operation
BasicBlock *QueryParent = QueryInst->getParent();
- Value *MemPtr = 0;
- uint64_t MemSize = 0;
-
// Do the scan.
if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
- // No dependence found. If this is the entry block of the function, it is a
- // clobber, otherwise it is non-local.
+ // No dependence found. If this is the entry block of the function, it is
+ // unknown, otherwise it is non-local.
if (QueryParent != &QueryParent->getParent()->getEntryBlock())
LocalCache = MemDepResult::getNonLocal();
else
- LocalCache = MemDepResult::getClobber(QueryInst);
- } else if (StoreInst *SI = dyn_cast<StoreInst>(QueryInst)) {
- // If this is a volatile store, don't mess around with it. Just return the
- // previous instruction as a clobber.
- if (SI->isVolatile())
- LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
- else {
- MemPtr = SI->getPointerOperand();
- MemSize = AA->getTypeStoreSize(SI->getOperand(0)->getType());
- }
- } else if (LoadInst *LI = dyn_cast<LoadInst>(QueryInst)) {
- // If this is a volatile load, don't mess around with it. Just return the
- // previous instruction as a clobber.
- if (LI->isVolatile())
- LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
- else {
- MemPtr = LI->getPointerOperand();
- MemSize = AA->getTypeStoreSize(LI->getType());
- }
- } else if (isFreeCall(QueryInst)) {
- MemPtr = QueryInst->getOperand(1);
- // calls to free() erase the entire structure, not just a field.
- MemSize = ~0UL;
- } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
- int IntrinsicID = 0; // Intrinsic IDs start at 1.
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
- IntrinsicID = II->getIntrinsicID();
-
- switch (IntrinsicID) {
- case Intrinsic::lifetime_start:
- case Intrinsic::lifetime_end:
- case Intrinsic::invariant_start:
- MemPtr = QueryInst->getOperand(2);
- MemSize = cast<ConstantInt>(QueryInst->getOperand(1))->getZExtValue();
- break;
- case Intrinsic::invariant_end:
- MemPtr = QueryInst->getOperand(3);
- MemSize = cast<ConstantInt>(QueryInst->getOperand(2))->getZExtValue();
- break;
- default:
- CallSite QueryCS = CallSite::get(QueryInst);
+ LocalCache = MemDepResult::getNonFuncLocal();
+ } else {
+ AliasAnalysis::Location MemLoc;
+ AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
+ if (MemLoc.Ptr) {
+ // If we can do a pointer scan, make it happen.
+ bool isLoad = !(MR & AliasAnalysis::Mod);
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
+ isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start;
+
+ LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos,
+ QueryParent);
+ } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
+ CallSite QueryCS(QueryInst);
bool isReadOnly = AA->onlyReadsMemory(QueryCS);
LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
QueryParent);
- break;
- }
- } else {
- // Non-memory instruction.
- LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
- }
-
- // If we need to do a pointer scan, make it happen.
- if (MemPtr) {
- bool isLoad = !QueryInst->mayWriteToMemory();
- if (IntrinsicInst *II = dyn_cast<MemoryUseIntrinsic>(QueryInst)) {
- isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_end;
- }
- LocalCache = getPointerDependencyFrom(MemPtr, MemSize, isLoad, ScanPos,
- QueryParent);
+ } else
+ // Non-memory instruction.
+ LocalCache = MemDepResult::getUnknown();
}
// Remember the result!
// Okay, we have a cache entry. If we know it is not dirty, just return it
// with no computation.
if (!CacheP.second) {
- NumCacheNonLocal++;
+ ++NumCacheNonLocal;
return Cache;
}
BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
DirtyBlocks.push_back(*PI);
- NumUncacheNonLocal++;
+ ++NumUncacheNonLocal;
}
// isReadonlyCall - If this is a read-only call, we can be more aggressive.
Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
} else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
// No dependence found. If this is the entry block of the function, it is
- // a clobber, otherwise it is non-local.
+ // a clobber, otherwise it is unknown.
Dep = MemDepResult::getNonLocal();
} else {
- Dep = MemDepResult::getClobber(ScanPos);
+ Dep = MemDepResult::getNonFuncLocal();
}
// If we had a dirty entry for the block, update it. Otherwise, just add
/// own block.
///
void MemoryDependenceAnalysis::
-getNonLocalPointerDependency(Value *Pointer, bool isLoad, BasicBlock *FromBB,
+getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad,
+ BasicBlock *FromBB,
SmallVectorImpl<NonLocalDepResult> &Result) {
- assert(Pointer->getType()->isPointerTy() &&
+ assert(Loc.Ptr->getType()->isPointerTy() &&
"Can't get pointer deps of a non-pointer!");
Result.clear();
- // We know that the pointer value is live into FromBB find the def/clobbers
- // from presecessors.
- const Type *EltTy = cast<PointerType>(Pointer->getType())->getElementType();
- uint64_t PointeeSize = AA->getTypeStoreSize(EltTy);
-
- PHITransAddr Address(Pointer, TD);
+ PHITransAddr Address(const_cast<Value *>(Loc.Ptr), TD);
// This is the set of blocks we've inspected, and the pointer we consider in
// each block. Because of critical edges, we currently bail out if querying
// a block with multiple different pointers. This can happen during PHI
// translation.
DenseMap<BasicBlock*, Value*> Visited;
- if (!getNonLocalPointerDepFromBB(Address, PointeeSize, isLoad, FromBB,
+ if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
Result, Visited, true))
return;
Result.clear();
Result.push_back(NonLocalDepResult(FromBB,
- MemDepResult::getClobber(FromBB->begin()),
- Pointer));
+ MemDepResult::getUnknown(),
+ const_cast<Value *>(Loc.Ptr)));
}
/// GetNonLocalInfoForBlock - Compute the memdep value for BB with
/// lookup (which may use dirty cache info if available). If we do a lookup,
/// add the result to the cache.
MemDepResult MemoryDependenceAnalysis::
-GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize,
+GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
bool isLoad, BasicBlock *BB,
NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
ScanPos = ExistingResult->getResult().getInst();
// Eliminating the dirty entry from 'Cache', so update the reverse info.
- ValueIsLoadPair CacheKey(Pointer, isLoad);
+ ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
} else {
++NumUncacheNonLocalPtr;
}
// Scan the block for the dependency.
- MemDepResult Dep = getPointerDependencyFrom(Pointer, PointeeSize, isLoad,
- ScanPos, BB);
+ MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);
// If we had a dirty entry for the block, update it. Otherwise, just add
// a new entry.
// If the block has a dependency (i.e. it isn't completely transparent to
// the value), remember the reverse association because we just added it
// to Cache!
- if (Dep.isNonLocal())
+ if (!Dep.isDef() && !Dep.isClobber())
return Dep;
// Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
// update MemDep when we remove instructions.
Instruction *Inst = Dep.getInst();
assert(Inst && "Didn't depend on anything?");
- ValueIsLoadPair CacheKey(Pointer, isLoad);
+ ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
return Dep;
}
/// not compute dependence information for some reason. This should be treated
/// as a clobber dependence on the first instruction in the predecessor block.
bool MemoryDependenceAnalysis::
-getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, uint64_t PointeeSize,
+getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
+ const AliasAnalysis::Location &Loc,
bool isLoad, BasicBlock *StartBB,
SmallVectorImpl<NonLocalDepResult> &Result,
DenseMap<BasicBlock*, Value*> &Visited,
// Look up the cached info for Pointer.
ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);
-
- std::pair<BBSkipFirstBlockPair, NonLocalDepInfo> *CacheInfo =
- &NonLocalPointerDeps[CacheKey];
- NonLocalDepInfo *Cache = &CacheInfo->second;
+
+ // Set up a temporary NLPI value. If the map doesn't yet have an entry for
+ // CacheKey, this value will be inserted as the associated value. Otherwise,
+ // it'll be ignored, and we'll have to check to see if the cached size and
+ // tbaa tag are consistent with the current query.
+ NonLocalPointerInfo InitialNLPI;
+ InitialNLPI.Size = Loc.Size;
+ InitialNLPI.TBAATag = Loc.TBAATag;
+
+ // Get the NLPI for CacheKey, inserting one into the map if it doesn't
+ // already have one.
+ std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
+ NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
+ NonLocalPointerInfo *CacheInfo = &Pair.first->second;
+
+ // If we already have a cache entry for this CacheKey, we may need to do some
+ // work to reconcile the cache entry and the current query.
+ if (!Pair.second) {
+ if (CacheInfo->Size < Loc.Size) {
+ // The query's Size is greater than the cached one. Throw out the
+ // cached data and proceed with the query at the greater size.
+ CacheInfo->Pair = BBSkipFirstBlockPair();
+ CacheInfo->Size = Loc.Size;
+ for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
+ DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
+ if (Instruction *Inst = DI->getResult().getInst())
+ RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
+ CacheInfo->NonLocalDeps.clear();
+ } else if (CacheInfo->Size > Loc.Size) {
+ // This query's Size is less than the cached one. Conservatively restart
+ // the query using the greater size.
+ return getNonLocalPointerDepFromBB(Pointer,
+ Loc.getWithNewSize(CacheInfo->Size),
+ isLoad, StartBB, Result, Visited,
+ SkipFirstBlock);
+ }
+
+ // If the query's TBAATag is inconsistent with the cached one,
+ // conservatively throw out the cached data and restart the query with
+ // no tag if needed.
+ if (CacheInfo->TBAATag != Loc.TBAATag) {
+ if (CacheInfo->TBAATag) {
+ CacheInfo->Pair = BBSkipFirstBlockPair();
+ CacheInfo->TBAATag = 0;
+ for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
+ DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
+ if (Instruction *Inst = DI->getResult().getInst())
+ RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
+ CacheInfo->NonLocalDeps.clear();
+ }
+ if (Loc.TBAATag)
+ return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
+ isLoad, StartBB, Result, Visited,
+ SkipFirstBlock);
+ }
+ }
+
+ NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;
// If we have valid cached information for exactly the block we are
// investigating, just return it with no recomputation.
- if (CacheInfo->first == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
+ if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
// We have a fully cached result for this query then we can just return the
// cached results and populate the visited set. However, we have to verify
// that we don't already have conflicting results for these blocks. Check
// than its valid cache info. If empty, the result will be valid cache info,
// otherwise it isn't.
if (Cache->empty())
- CacheInfo->first = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
+ CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
else
- CacheInfo->first = BBSkipFirstBlockPair();
+ CacheInfo->Pair = BBSkipFirstBlockPair();
SmallVector<BasicBlock*, 32> Worklist;
Worklist.push_back(StartBB);
+ // PredList used inside loop.
+ SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList;
+
// Keep track of the entries that we know are sorted. Previously cached
// entries will all be sorted. The entries we add we only sort on demand (we
// don't insert every element into its sorted position). We know that we
// Get the dependency info for Pointer in BB. If we have cached
// information, we will use it, otherwise we compute it.
DEBUG(AssertSorted(*Cache, NumSortedEntries));
- MemDepResult Dep = GetNonLocalInfoForBlock(Pointer.getAddr(), PointeeSize,
- isLoad, BB, Cache,
+ MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
NumSortedEntries);
// If we got a Def or Clobber, add this to the list of results.
// the same Pointer.
if (!Pointer.NeedsPHITranslationFromBlock(BB)) {
SkipFirstBlock = false;
+ SmallVector<BasicBlock*, 16> NewBlocks;
for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
// Verify that we haven't looked at this block yet.
std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr()));
if (InsertRes.second) {
// First time we've looked at *PI.
- Worklist.push_back(*PI);
+ NewBlocks.push_back(*PI);
continue;
}
// If we have seen this block before, but it was with a different
// pointer then we have a phi translation failure and we have to treat
// this as a clobber.
- if (InsertRes.first->second != Pointer.getAddr())
+ if (InsertRes.first->second != Pointer.getAddr()) {
+ // Make sure to clean up the Visited map before continuing on to
+ // PredTranslationFailure.
+ for (unsigned i = 0; i < NewBlocks.size(); i++)
+ Visited.erase(NewBlocks[i]);
goto PredTranslationFailure;
+ }
}
+ Worklist.append(NewBlocks.begin(), NewBlocks.end());
continue;
}
NumSortedEntries = Cache->size();
}
Cache = 0;
-
+
+ PredList.clear();
for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
BasicBlock *Pred = *PI;
-
+ PredList.push_back(std::make_pair(Pred, Pointer));
+
// Get the PHI translated pointer in this predecessor. This can fail if
// not translatable, in which case the getAddr() returns null.
- PHITransAddr PredPointer(Pointer);
+ PHITransAddr &PredPointer = PredList.back().second;
PredPointer.PHITranslateValue(BB, Pred, 0);
Value *PredPtrVal = PredPointer.getAddr();
InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal));
if (!InsertRes.second) {
+ // We found the pred; take it off the list of preds to visit.
+ PredList.pop_back();
+
// If the predecessor was visited with PredPtr, then we already did
// the analysis and can ignore it.
if (InsertRes.first->second == PredPtrVal)
// Otherwise, the block was previously analyzed with a different
// pointer. We can't represent the result of this case, so we just
// treat this as a phi translation failure.
+
+ // Make sure to clean up the Visited map before continuing on to
+ // PredTranslationFailure.
+ for (unsigned i = 0; i < PredList.size(); i++)
+ Visited.erase(PredList[i].first);
+
goto PredTranslationFailure;
}
-
+ }
+
+ // Actually process results here; this need to be a separate loop to avoid
+ // calling getNonLocalPointerDepFromBB for blocks we don't want to return
+ // any results for. (getNonLocalPointerDepFromBB will modify our
+ // datastructures in ways the code after the PredTranslationFailure label
+ // doesn't expect.)
+ for (unsigned i = 0; i < PredList.size(); i++) {
+ BasicBlock *Pred = PredList[i].first;
+ PHITransAddr &PredPointer = PredList[i].second;
+ Value *PredPtrVal = PredPointer.getAddr();
+
+ bool CanTranslate = true;
// If PHI translation was unable to find an available pointer in this
// predecessor, then we have to assume that the pointer is clobbered in
// that predecessor. We can still do PRE of the load, which would insert
// a computation of the pointer in this predecessor.
- if (PredPtrVal == 0) {
+ if (PredPtrVal == 0)
+ CanTranslate = false;
+
+ // FIXME: it is entirely possible that PHI translating will end up with
+ // the same value. Consider PHI translating something like:
+ // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
+ // to recurse here, pedantically speaking.
+
+ // If getNonLocalPointerDepFromBB fails here, that means the cached
+ // result conflicted with the Visited list; we have to conservatively
+ // assume it is unknown, but this also does not block PRE of the load.
+ if (!CanTranslate ||
+ getNonLocalPointerDepFromBB(PredPointer,
+ Loc.getWithNewPtr(PredPtrVal),
+ isLoad, Pred,
+ Result, Visited)) {
// Add the entry to the Result list.
- NonLocalDepResult Entry(Pred,
- MemDepResult::getClobber(Pred->getTerminator()),
- PredPtrVal);
+ NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
Result.push_back(Entry);
// Since we had a phi translation failure, the cache for CacheKey won't
// queries. Mark this in NonLocalPointerDeps by setting the
// BBSkipFirstBlockPair pointer to null. This requires reuse of the
// cached value to do more work but not miss the phi trans failure.
- NonLocalPointerDeps[CacheKey].first = BBSkipFirstBlockPair();
+ NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
+ NLPI.Pair = BBSkipFirstBlockPair();
continue;
}
-
- // FIXME: it is entirely possible that PHI translating will end up with
- // the same value. Consider PHI translating something like:
- // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
- // to recurse here, pedantically speaking.
-
- // If we have a problem phi translating, fall through to the code below
- // to handle the failure condition.
- if (getNonLocalPointerDepFromBB(PredPointer, PointeeSize, isLoad, Pred,
- Result, Visited))
- goto PredTranslationFailure;
}
// Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
CacheInfo = &NonLocalPointerDeps[CacheKey];
- Cache = &CacheInfo->second;
+ Cache = &CacheInfo->NonLocalDeps;
NumSortedEntries = Cache->size();
// Since we did phi translation, the "Cache" set won't contain all of the
// results for the query. This is ok (we can still use it to accelerate
// specific block queries) but we can't do the fastpath "return all
// results from the set" Clear out the indicator for this.
- CacheInfo->first = BBSkipFirstBlockPair();
+ CacheInfo->Pair = BBSkipFirstBlockPair();
SkipFirstBlock = false;
continue;
PredTranslationFailure:
+ // The following code is "failure"; we can't produce a sane translation
+ // for the given block. It assumes that we haven't modified any of
+ // our datastructures while processing the current block.
if (Cache == 0) {
// Refresh the CacheInfo/Cache pointer if it got invalidated.
CacheInfo = &NonLocalPointerDeps[CacheKey];
- Cache = &CacheInfo->second;
+ Cache = &CacheInfo->NonLocalDeps;
NumSortedEntries = Cache->size();
}
// results for the query. This is ok (we can still use it to accelerate
// specific block queries) but we can't do the fastpath "return all
// results from the set". Clear out the indicator for this.
- CacheInfo->first = BBSkipFirstBlockPair();
+ CacheInfo->Pair = BBSkipFirstBlockPair();
- // If *nothing* works, mark the pointer as being clobbered by the first
- // instruction in this block.
+ // If *nothing* works, mark the pointer as unknown.
//
// If this is the magic first block, return this as a clobber of the whole
// incoming value. Since we can't phi translate to one of the predecessors,
assert(I->getResult().isNonLocal() &&
"Should only be here with transparent block");
- I->setResult(MemDepResult::getClobber(BB->begin()));
- ReverseNonLocalPtrDeps[BB->begin()].insert(CacheKey);
+ I->setResult(MemDepResult::getUnknown());
Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
Pointer.getAddr()));
break;
// Remove all of the entries in the BB->val map. This involves removing
// instructions from the reverse map.
- NonLocalDepInfo &PInfo = It->second.second;
+ NonLocalDepInfo &PInfo = It->second.NonLocalDeps;
for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
Instruction *Target = PInfo[i].getResult().getInst();
assert(P.getPointer() != RemInst &&
"Already removed NonLocalPointerDeps info for RemInst");
- NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].second;
+ NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps;
// The cache is not valid for any specific block anymore.
- NonLocalPointerDeps[P].first = BBSkipFirstBlockPair();
+ NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();
// Update any entries for RemInst to use the instruction after it.
for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
E = NonLocalPointerDeps.end(); I != E; ++I) {
assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
- const NonLocalDepInfo &Val = I->second.second;
+ const NonLocalDepInfo &Val = I->second.NonLocalDeps;
for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
II != E; ++II)
assert(II->getResult().getInst() != D && "Inst occurs as NLPD value");
projects / oota-llvm.git / blobdiff