Revert r176408 and r176407 to address PR15540.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179111 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index ae6da1a..f8509dd 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -88,7 +88,7 @@
const TargetLibraryInfo &TLI,
bool RoundToAlign = false) {
uint64_t Size;
- if (getUnderlyingObjectSize(V, Size, &TD, &TLI, RoundToAlign))
+ if (getObjectSize(V, Size, &TD, &TLI, RoundToAlign))
return Size;
return AliasAnalysis::UnknownSize;
}
@@ -98,6 +98,35 @@
static bool isObjectSmallerThan(const Value *V, uint64_t Size,
const DataLayout &TD,
const TargetLibraryInfo &TLI) {
+ // Note that the meanings of the "object" are slightly different in the
+ // following contexts:
+ // c1: llvm::getObjectSize()
+ // c2: llvm.objectsize() intrinsic
+ // c3: isObjectSmallerThan()
+ // c1 and c2 share the same meaning; however, the meaning of "object" in c3
+ // refers to the "entire object".
+ //
+ // Consider this example:
+ // char *p = (char*)malloc(100)
+ // char *q = p+80;
+ //
+ // In the context of c1 and c2, the "object" pointed by q refers to the
+ // stretch of memory of q[0:19]. So, getObjectSize(q) should return 20.
+ //
+ // However, in the context of c3, the "object" refers to the chunk of memory
+ // being allocated. So, the "object" has 100 bytes, and q points to the middle
+ // the "object". In case q is passed to isObjectSmallerThan() as the 1st
+ // parameter, before the llvm::getObjectSize() is called to get the size of
+ // entire object, we should:
+ // - either rewind the pointer q to the base-address of the object in
+ // question (in this case rewind to p), or
+ // - just give up. It is up to caller to make sure the pointer is pointing
+ // to the base address the object.
+ //
+ // We go for 2nd option for simplicity.
+ if (!isIdentifiedObject(V))
+ return false;
+
// This function needs to use the aligned object size because we allow
// reads a bit past the end given sufficient alignment.
uint64_t ObjectSize = getObjectSize(V, TD, TLI, /*RoundToAlign*/true);
diff --git a/lib/Analysis/MemoryBuiltins.cpp b/lib/Analysis/MemoryBuiltins.cpp
index d490d54..9c0d8ac 100644
--- a/lib/Analysis/MemoryBuiltins.cpp
+++ b/lib/Analysis/MemoryBuiltins.cpp
@@ -364,26 +364,6 @@
return true;
}
-/// \brief Compute the size of the underlying object pointed by Ptr. Returns
-/// true and the object size in Size if successful, and false otherwise.
-/// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
-/// byval arguments, and global variables.
-bool llvm::getUnderlyingObjectSize(const Value *Ptr, uint64_t &Size,
- const DataLayout *TD,
- const TargetLibraryInfo *TLI,
- bool RoundToAlign) {
- if (!TD)
- return false;
-
- ObjectSizeOffsetVisitor Visitor(TD, TLI, Ptr->getContext(), RoundToAlign);
- SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
- if (!Visitor.knownSize(Data))
- return false;
-
- Size = Data.first.getZExtValue();
- return true;
-}
-
STATISTIC(ObjectVisitorArgument,
"Number of arguments with unsolved size and offset");
@@ -409,23 +389,16 @@
SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
V = V->stripPointerCasts();
+ if (Instruction *I = dyn_cast<Instruction>(V)) {
+ // If we have already seen this instruction, bail out. Cycles can happen in
+ // unreachable code after constant propagation.
+ if (!SeenInsts.insert(I))
+ return unknown();
- if (isa<Instruction>(V) || isa<GEPOperator>(V)) {
- // Return cached value or insert unknown in cache if size of V was not
- // computed yet in order to avoid recursions in PHis.
- std::pair<CacheMapTy::iterator, bool> CacheVal =
- CacheMap.insert(std::make_pair(V, unknown()));
- if (!CacheVal.second)
- return CacheVal.first->second;
-
- SizeOffsetType Result;
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
- Result = visitGEPOperator(*GEP);
- else
- Result = visit(cast<Instruction>(*V));
- return CacheMap[V] = Result;
+ return visitGEPOperator(*GEP);
+ return visit(*I);
}
-
if (Argument *A = dyn_cast<Argument>(V))
return visitArgument(*A);
if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
@@ -439,6 +412,8 @@
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->getOpcode() == Instruction::IntToPtr)
return unknown(); // clueless
+ if (CE->getOpcode() == Instruction::GetElementPtr)
+ return visitGEPOperator(cast<GEPOperator>(*CE));
}
DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
@@ -572,21 +547,9 @@
return unknown();
}
-SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode &PHI) {
- if (PHI.getNumIncomingValues() == 0)
- return unknown();
-
- SizeOffsetType Ret = compute(PHI.getIncomingValue(0));
- if (!bothKnown(Ret))
- return unknown();
-
- // Verify that all PHI incoming pointers have the same size and offset.
- for (unsigned i = 1, e = PHI.getNumIncomingValues(); i != e; ++i) {
- SizeOffsetType EdgeData = compute(PHI.getIncomingValue(i));
- if (!bothKnown(EdgeData) || EdgeData != Ret)
- return unknown();
- }
- return Ret;
+SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
+ // too complex to analyze statically.
+ return unknown();
}
SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {