#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/GlobalAlias.h"
-#include "llvm/GlobalVariable.h"
-#include "llvm/IntrinsicInst.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/GlobalAlias.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Operator.h"
using namespace llvm;
/// AreEquivalentAddressValues - Test if A and B will obviously have the same
static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
// Test if the values are trivially equivalent.
if (A == B) return true;
-
+
// Test if the values come from identical arithmetic instructions.
// Use isIdenticalToWhenDefined instead of isIdenticalTo because
// this function is only used when one address use dominates the
if (const Instruction *BI = dyn_cast<Instruction>(B))
if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
return true;
-
+
// Otherwise they may not be equivalent.
return false;
}
-/// getUnderlyingObjectWithOffset - Strip off up to MaxLookup GEPs and
-/// bitcasts to get back to the underlying object being addressed, keeping
-/// track of the offset in bytes from the GEPs relative to the result.
-/// This is closely related to Value::getUnderlyingObject but is located
-/// here to avoid making VMCore depend on TargetData.
-static Value *getUnderlyingObjectWithOffset(Value *V, const TargetData *TD,
- uint64_t &ByteOffset,
- unsigned MaxLookup = 6) {
- if (!V->getType()->isPointerTy())
- return V;
- for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
- if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
- if (!GEP->hasAllConstantIndices())
- return V;
- SmallVector<Value*, 8> Indices(GEP->op_begin() + 1, GEP->op_end());
- ByteOffset += TD->getIndexedOffset(GEP->getPointerOperandType(),
- &Indices[0], Indices.size());
- V = GEP->getPointerOperand();
- } else if (Operator::getOpcode(V) == Instruction::BitCast) {
- V = cast<Operator>(V)->getOperand(0);
- } else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
- if (GA->mayBeOverridden())
- return V;
- V = GA->getAliasee();
- } else {
- return V;
- }
- assert(V->getType()->isPointerTy() && "Unexpected operand type!");
- }
- return V;
-}
-
/// isSafeToLoadUnconditionally - Return true if we know that executing a load
/// from this value cannot trap. If it is not obviously safe to load from the
/// specified pointer, we do a quick local scan of the basic block containing
/// ScanFrom, to determine if the address is already accessed.
bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom,
- unsigned Align, const TargetData *TD) {
- uint64_t ByteOffset = 0;
+ unsigned Align, const DataLayout *TD) {
+ int64_t ByteOffset = 0;
Value *Base = V;
- if (TD)
- Base = getUnderlyingObjectWithOffset(V, TD, ByteOffset);
+ Base = GetPointerBaseWithConstantOffset(V, ByteOffset, TD);
- const Type *BaseType = 0;
+ if (ByteOffset < 0) // out of bounds
+ return false;
+
+ Type *BaseType = nullptr;
unsigned BaseAlign = 0;
if (const AllocaInst *AI = dyn_cast<AllocaInst>(Base)) {
// An alloca is safe to load from as load as it is suitably aligned.
BaseType = AI->getAllocatedType();
BaseAlign = AI->getAlignment();
- } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(Base)) {
+ } else if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
// Global variables are safe to load from but their size cannot be
// guaranteed if they are overridden.
- if (!isa<GlobalAlias>(GV) && !GV->mayBeOverridden()) {
+ if (!GV->mayBeOverridden()) {
BaseType = GV->getType()->getElementType();
BaseAlign = GV->getAlignment();
}
return true; // Loading directly from an alloca or global is OK.
// Check if the load is within the bounds of the underlying object.
-
const PointerType *AddrTy = cast<PointerType>(V->getType());
+ PointerType *AddrTy = cast<PointerType>(V->getType());
uint64_t LoadSize = TD->getTypeStoreSize(AddrTy->getElementType());
if (ByteOffset + LoadSize <= TD->getTypeAllocSize(BaseType) &&
(Align == 0 || (ByteOffset % Align) == 0))
/// MaxInstsToScan specifies the maximum instructions to scan in the block. If
/// it is set to 0, it will scan the whole block. You can also optionally
/// specify an alias analysis implementation, which makes this more precise.
+///
+/// If AATags is non-null and a load or store is found, the AA tags from the
+/// load or store are recorded there. If there are no AA tags or if no access
+/// is found, it is left unmodified.
Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
BasicBlock::iterator &ScanFrom,
unsigned MaxInstsToScan,
- AliasAnalysis *AA) {
+ AliasAnalysis *AA,
+ AAMDNodes *AATags) {
if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
// If we're using alias analysis to disambiguate get the size of *Ptr.
uint64_t AccessSize = 0;
if (AA) {
-
const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
+ Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
AccessSize = AA->getTypeStoreSize(AccessTy);
}
ScanFrom++;
// Don't scan huge blocks.
- if (MaxInstsToScan-- == 0) return 0;
+ if (MaxInstsToScan-- == 0) return nullptr;
--ScanFrom;
// If this is a load of Ptr, the loaded value is available.
+ // (This is true even if the load is volatile or atomic, although
+ // those cases are unlikely.)
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
- if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
+ if (AreEquivalentAddressValues(LI->getOperand(0), Ptr)) {
+ if (AATags) LI->getAAMetadata(*AATags);
return LI;
+ }
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
// If this is a store through Ptr, the value is available!
- if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
+ // (This is true even if the store is volatile or atomic, although
+ // those cases are unlikely.)
+ if (AreEquivalentAddressValues(SI->getOperand(1), Ptr)) {
+ if (AATags) SI->getAAMetadata(*AATags);
return SI->getOperand(0);
+ }
// If Ptr is an alloca and this is a store to a different alloca, ignore
// the store. This is a trivial form of alias analysis that is important
// Otherwise the store that may or may not alias the pointer, bail out.
++ScanFrom;
- return 0;
+ return nullptr;
}
// If this is some other instruction that may clobber Ptr, bail out.
// May modify the pointer, bail out.
++ScanFrom;
- return 0;
+ return nullptr;
}
}
// Got to the start of the block, we didn't find it, but are done for this
// block.
- return 0;
+ return nullptr;
}
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