Extracted ObjCARCContract from ObjCARCOpts into its own file.
This also required adding 2x headers Dependency Analysis.h/Provenance Analysis.h
and a .cpp file DependencyAnalysis.cpp to unentangle the dependencies inbetween
ObjCARCContract and ObjCARCOpts.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173760 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp b/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp
new file mode 100644
index 0000000..79a90c6
--- /dev/null
+++ b/lib/Transforms/ObjCARC/ProvenanceAnalysis.cpp
@@ -0,0 +1,177 @@
+//===- ProvenanceAnalysis.cpp - ObjC ARC Optimization ---------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This file defines a special form of Alias Analysis called ``Provenance
+/// Analysis''. The word ``provenance'' refers to the history of the ownership
+/// of an object. Thus ``Provenance Analysis'' is an analysis which attempts to
+/// use various techniques to determine if locally
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+#include "ObjCARC.h"
+#include "ProvenanceAnalysis.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/STLExtras.h"
+
+using namespace llvm;
+using namespace llvm::objcarc;
+
+bool ProvenanceAnalysis::relatedSelect(const SelectInst *A,
+ const Value *B) {
+ // If the values are Selects with the same condition, we can do a more precise
+ // check: just check for relations between the values on corresponding arms.
+ if (const SelectInst *SB = dyn_cast<SelectInst>(B))
+ if (A->getCondition() == SB->getCondition())
+ return related(A->getTrueValue(), SB->getTrueValue()) ||
+ related(A->getFalseValue(), SB->getFalseValue());
+
+ // Check both arms of the Select node individually.
+ return related(A->getTrueValue(), B) ||
+ related(A->getFalseValue(), B);
+}
+
+bool ProvenanceAnalysis::relatedPHI(const PHINode *A,
+ const Value *B) {
+ // If the values are PHIs in the same block, we can do a more precise as well
+ // as efficient check: just check for relations between the values on
+ // corresponding edges.
+ if (const PHINode *PNB = dyn_cast<PHINode>(B))
+ if (PNB->getParent() == A->getParent()) {
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
+ if (related(A->getIncomingValue(i),
+ PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
+ return true;
+ return false;
+ }
+
+ // Check each unique source of the PHI node against B.
+ SmallPtrSet<const Value *, 4> UniqueSrc;
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
+ const Value *PV1 = A->getIncomingValue(i);
+ if (UniqueSrc.insert(PV1) && related(PV1, B))
+ return true;
+ }
+
+ // All of the arms checked out.
+ return false;
+}
+
+/// Test if the value of P, or any value covered by its provenance, is ever
+/// stored within the function (not counting callees).
+static bool isStoredObjCPointer(const Value *P) {
+ SmallPtrSet<const Value *, 8> Visited;
+ SmallVector<const Value *, 8> Worklist;
+ Worklist.push_back(P);
+ Visited.insert(P);
+ do {
+ P = Worklist.pop_back_val();
+ for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
+ UI != UE; ++UI) {
+ const User *Ur = *UI;
+ if (isa<StoreInst>(Ur)) {
+ if (UI.getOperandNo() == 0)
+ // The pointer is stored.
+ return true;
+ // The pointed is stored through.
+ continue;
+ }
+ if (isa<CallInst>(Ur))
+ // The pointer is passed as an argument, ignore this.
+ continue;
+ if (isa<PtrToIntInst>(P))
+ // Assume the worst.
+ return true;
+ if (Visited.insert(Ur))
+ Worklist.push_back(Ur);
+ }
+ } while (!Worklist.empty());
+
+ // Everything checked out.
+ return false;
+}
+
+bool ProvenanceAnalysis::relatedCheck(const Value *A,
+ const Value *B) {
+ // Skip past provenance pass-throughs.
+ A = GetUnderlyingObjCPtr(A);
+ B = GetUnderlyingObjCPtr(B);
+
+ // Quick check.
+ if (A == B)
+ return true;
+
+ // Ask regular AliasAnalysis, for a first approximation.
+ switch (AA->alias(A, B)) {
+ case AliasAnalysis::NoAlias:
+ return false;
+ case AliasAnalysis::MustAlias:
+ case AliasAnalysis::PartialAlias:
+ return true;
+ case AliasAnalysis::MayAlias:
+ break;
+ }
+
+ bool AIsIdentified = IsObjCIdentifiedObject(A);
+ bool BIsIdentified = IsObjCIdentifiedObject(B);
+
+ // An ObjC-Identified object can't alias a load if it is never locally stored.
+ if (AIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(B))
+ return isStoredObjCPointer(A);
+ if (BIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ // Both pointers are identified and escapes aren't an evident problem.
+ return false;
+ }
+ } else if (BIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ }
+
+ // Special handling for PHI and Select.
+ if (const PHINode *PN = dyn_cast<PHINode>(A))
+ return relatedPHI(PN, B);
+ if (const PHINode *PN = dyn_cast<PHINode>(B))
+ return relatedPHI(PN, A);
+ if (const SelectInst *S = dyn_cast<SelectInst>(A))
+ return relatedSelect(S, B);
+ if (const SelectInst *S = dyn_cast<SelectInst>(B))
+ return relatedSelect(S, A);
+
+ // Conservative.
+ return true;
+}
+
+bool ProvenanceAnalysis::related(const Value *A,
+ const Value *B) {
+ // Begin by inserting a conservative value into the map. If the insertion
+ // fails, we have the answer already. If it succeeds, leave it there until we
+ // compute the real answer to guard against recursive queries.
+ if (A > B) std::swap(A, B);
+ std::pair<CachedResultsTy::iterator, bool> Pair =
+ CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
+ if (!Pair.second)
+ return Pair.first->second;
+
+ bool Result = relatedCheck(A, B);
+ CachedResults[ValuePairTy(A, B)] = Result;
+ return Result;
+}