merge of use-diet branch to trunk

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50943 91177308-0d34-0410-b5e6-96231b3b80d8

lib/VMCore/Use.cpp

@@ -0,0 +1,131 @@
+//===-- Use.cpp - Implement the Use class -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the algorithm for finding the User of a Use.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/User.h"
+
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+//                         Use getImpliedUser Implementation
+//===----------------------------------------------------------------------===//
+
+const Use *Use::getImpliedUser() const {
+  const Use *Current = this;
+
+  while (true) {
+    unsigned Tag = extractTag<PrevPtrTag, fullStopTag>((Current++)->Prev);
+    switch (Tag) {
+      case zeroDigitTag:
+      case oneDigitTag:
+        continue;
+
+      case stopTag: {
+        ++Current;
+        ptrdiff_t Offset = 1;
+        while (true) {
+          unsigned Tag = extractTag<PrevPtrTag, fullStopTag>(Current->Prev);
+          switch (Tag) {
+            case zeroDigitTag:
+            case oneDigitTag:
+              ++Current;
+              Offset = (Offset << 1) + Tag;
+              continue;
+            default:
+              return Current + Offset;
+          }
+        }
+      }
+
+      case fullStopTag:
+        return Current;
+    }
+  }
+}
+
+//===----------------------------------------------------------------------===//
+//                         Use initTags Implementation
+//===----------------------------------------------------------------------===//
+
+Use *Use::initTags(Use * const Start, Use *Stop, ptrdiff_t Done) {
+  ptrdiff_t Count = Done;
+  while (Start != Stop) {
+    --Stop;
+    Stop->Val = 0;
+    if (!Count) {
+      Stop->Prev = reinterpret_cast<Use**>(Done == 0 ? fullStopTag : stopTag);
+      ++Done;
+      Count = Done;
+    } else {
+      Stop->Prev = reinterpret_cast<Use**>(Count & 1);
+      Count >>= 1;
+      ++Done;
+    }
+  }
+
+  return Start;
+}
+
+//===----------------------------------------------------------------------===//
+//                         Use zap Implementation
+//===----------------------------------------------------------------------===//
+
+void Use::zap(Use *Start, const Use *Stop, bool del) {
+  if (del) {
+    while (Start != Stop) {
+      (--Stop)->~Use();
+    }
+    ::operator delete(Start);
+    return;
+  }
+
+  while (Start != Stop) {
+    (Start++)->set(0);
+  }
+}
+
+//===----------------------------------------------------------------------===//
+//                         AugmentedUse layout struct
+//===----------------------------------------------------------------------===//
+
+struct AugmentedUse : Use {
+  User *ref;
+  AugmentedUse(); // not implemented
+};
+
+
+//===----------------------------------------------------------------------===//
+//                         Use getUser Implementation
+//===----------------------------------------------------------------------===//
+
+User *Use::getUser() const {
+  const Use *End = getImpliedUser();
+  User *She = static_cast<const AugmentedUse*>(End - 1)->ref;
+  She = extractTag<Tag, tagOne>(She)
+      ? llvm::stripTag<tagOne>(She)
+      : reinterpret_cast<User*>(const_cast<Use*>(End));
+
+  return She;
+}
+
+//===----------------------------------------------------------------------===//
+//                         User allocHungoffUses Implementation
+//===----------------------------------------------------------------------===//
+
+Use *User::allocHungoffUses(unsigned N) const {
+  Use *Begin = static_cast<Use*>(::operator new(sizeof(Use) * N + sizeof(AugmentedUse) - sizeof(Use)));
+  Use *End = Begin + N;
+  static_cast<AugmentedUse&>(End[-1]).ref = addTag(this, tagOne);
+  return Use::initTags(Begin, End);
+}
+
+} // End llvm namespace