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diff --git a/contrib/llvm/lib/Analysis/CaptureTracking.cpp b/contrib/llvm/lib/Analysis/CaptureTracking.cpp
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+//===--- CaptureTracking.cpp - Determine whether a pointer is captured ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains routines that help determine which pointers are captured.
+// A pointer value is captured if the function makes a copy of any part of the
+// pointer that outlives the call.  Not being captured means, more or less, that
+// the pointer is only dereferenced and not stored in a global.  Returning part
+// of the pointer as the function return value may or may not count as capturing
+// the pointer, depending on the context.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Instructions.h"
+#include "llvm/Value.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/CallSite.h"
+using namespace llvm;
+
+/// As its comment mentions, PointerMayBeCaptured can be expensive.
+/// However, it's not easy for BasicAA to cache the result, because
+/// it's an ImmutablePass. To work around this, bound queries at a
+/// fixed number of uses.
+///
+/// TODO: Write a new FunctionPass AliasAnalysis so that it can keep
+/// a cache. Then we can move the code from BasicAliasAnalysis into
+/// that path, and remove this threshold.
+static int const Threshold = 20;
+
+/// PointerMayBeCaptured - Return true if this pointer value may be captured
+/// by the enclosing function (which is required to exist).  This routine can
+/// be expensive, so consider caching the results.  The boolean ReturnCaptures
+/// specifies whether returning the value (or part of it) from the function
+/// counts as capturing it or not.  The boolean StoreCaptures specified whether
+/// storing the value (or part of it) into memory anywhere automatically
+/// counts as capturing it or not.
+bool llvm::PointerMayBeCaptured(const Value *V,
+                                bool ReturnCaptures, bool StoreCaptures) {
+  assert(V->getType()->isPointerTy() && "Capture is for pointers only!");
+  SmallVector<Use*, Threshold> Worklist;
+  SmallSet<Use*, Threshold> Visited;
+  int Count = 0;
+
+  for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
+       UI != UE; ++UI) {
+    // If there are lots of uses, conservatively say that the value
+    // is captured to avoid taking too much compile time.
+    if (Count++ >= Threshold)
+      return true;
+
+    Use *U = &UI.getUse();
+    Visited.insert(U);
+    Worklist.push_back(U);
+  }
+
+  while (!Worklist.empty()) {
+    Use *U = Worklist.pop_back_val();
+    Instruction *I = cast<Instruction>(U->getUser());
+    V = U->get();
+
+    switch (I->getOpcode()) {
+    case Instruction::Call:
+    case Instruction::Invoke: {
+      CallSite CS(I);
+      // Not captured if the callee is readonly, doesn't return a copy through
+      // its return value and doesn't unwind (a readonly function can leak bits
+      // by throwing an exception or not depending on the input value).
+      if (CS.onlyReadsMemory() && CS.doesNotThrow() && I->getType()->isVoidTy())
+        break;
+
+      // Not captured if only passed via 'nocapture' arguments.  Note that
+      // calling a function pointer does not in itself cause the pointer to
+      // be captured.  This is a subtle point considering that (for example)
+      // the callee might return its own address.  It is analogous to saying
+      // that loading a value from a pointer does not cause the pointer to be
+      // captured, even though the loaded value might be the pointer itself
+      // (think of self-referential objects).
+      CallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
+      for (CallSite::arg_iterator A = B; A != E; ++A)
+        if (A->get() == V && !CS.paramHasAttr(A - B + 1, Attribute::NoCapture))
+          // The parameter is not marked 'nocapture' - captured.
+          return true;
+      // Only passed via 'nocapture' arguments, or is the called function - not
+      // captured.
+      break;
+    }
+    case Instruction::Load:
+      // Loading from a pointer does not cause it to be captured.
+      break;
+    case Instruction::Ret:
+      if (ReturnCaptures)
+        return true;
+      break;
+    case Instruction::Store:
+      if (V == I->getOperand(0))
+        // Stored the pointer - conservatively assume it may be captured.
+        // TODO: If StoreCaptures is not true, we could do Fancy analysis
+        // to determine whether this store is not actually an escape point.
+        // In that case, BasicAliasAnalysis should be updated as well to
+        // take advantage of this.
+        return true;
+      // Storing to the pointee does not cause the pointer to be captured.
+      break;
+    case Instruction::BitCast:
+    case Instruction::GetElementPtr:
+    case Instruction::PHI:
+    case Instruction::Select:
+      // The original value is not captured via this if the new value isn't.
+      for (Instruction::use_iterator UI = I->use_begin(), UE = I->use_end();
+           UI != UE; ++UI) {
+        Use *U = &UI.getUse();
+        if (Visited.insert(U))
+          Worklist.push_back(U);
+      }
+      break;
+    case Instruction::ICmp:
+      // Don't count comparisons of a no-alias return value against null as
+      // captures. This allows us to ignore comparisons of malloc results
+      // with null, for example.
+      if (isNoAliasCall(V->stripPointerCasts()))
+        if (ConstantPointerNull *CPN =
+              dyn_cast<ConstantPointerNull>(I->getOperand(1)))
+          if (CPN->getType()->getAddressSpace() == 0)
+            break;
+      // Otherwise, be conservative. There are crazy ways to capture pointers
+      // using comparisons.
+      return true;
+    default:
+      // Something else - be conservative and say it is captured.
+      return true;
+    }
+  }
+
+  // All uses examined - not captured.
+  return false;
+}