Reapply "[ORC] Add "wrap" and "unwrap" steps to ExecutorAddr..." with…

… fixes.

Reapplies f14cb49 (which was reverted in 2f08f84) with a fix for UB in
the ExecutorAddr::Unwrap::Unwrap constructor (which caused failures on some
bots).

llvm/include/llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h

@@ -14,6 +14,7 @@
 #define LLVM_EXECUTIONENGINE_ORC_SHARED_EXECUTORADDRESS_H
 
 #include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/identity.h"
 #include "llvm/ExecutionEngine/Orc/Shared/SimplePackedSerialization.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/raw_ostream.h"
@@ -29,34 +30,76 @@ using ExecutorAddrDiff = uint64_t;
 /// Represents an address in the executor process.
 class ExecutorAddr {
 public:
+  /// A wrap/unwrap function that leaves pointers unmodified.
+  template <typename T> using rawPtr = llvm::identity<T>;
+
+  /// Default wrap function to use on this host.
+  template <typename T> using defaultWrap = rawPtr<T>;
+
+  /// Default unwrap function to use on this host.
+  template <typename T> using defaultUnwrap = rawPtr<T>;
+
+  /// Merges a tag into the raw address value:
+  ///   P' = P | (TagValue << TagOffset).
+  class Tag {
+  public:
+    constexpr Tag(uintptr_t TagValue, uintptr_t TagOffset)
+        : TagMask(TagValue << TagOffset) {}
+
+    template <typename T> constexpr T *operator()(T *P) {
+      return reinterpret_cast<T *>(reinterpret_cast<uintptr_t>(P) | TagMask);
+    }
+
+  private:
+    uintptr_t TagMask;
+  };
+
+  /// Strips a tag of the given length from the given offset within the pointer:
+  /// P' = P & ~(((1 << TagLen) -1) << TagOffset)
+  class Untag {
+  public:
+    constexpr Untag(uintptr_t TagLen, uintptr_t TagOffset)
+        : UntagMask(~(((uintptr_t(1) << TagLen) - 1) << TagOffset)) {}
+
+    template <typename T> constexpr T *operator()(T *P) {
+      return reinterpret_cast<T *>(reinterpret_cast<uintptr_t>(P) & UntagMask);
+    }
+
+  private:
+    uintptr_t UntagMask;
+  };
+
   ExecutorAddr() = default;
 
   /// Create an ExecutorAddr from the given value.
   explicit constexpr ExecutorAddr(uint64_t Addr) : Addr(Addr) {}
 
   /// Create an ExecutorAddr from the given pointer.
   /// Warning: This should only be used when JITing in-process.
-  template <typename T> static ExecutorAddr fromPtr(T *Value) {
+  template <typename T, typename UnwrapFn = defaultUnwrap<T *>>
+  static ExecutorAddr fromPtr(T *Ptr, UnwrapFn &&Unwrap = UnwrapFn()) {
     return ExecutorAddr(
-        static_cast<uint64_t>(reinterpret_cast<uintptr_t>(Value)));
+        static_cast<uint64_t>(reinterpret_cast<uintptr_t>(Unwrap(Ptr))));
   }
 
   /// Cast this ExecutorAddr to a pointer of the given type.
   /// Warning: This should only be used when JITing in-process.
-  template <typename T>
-  std::enable_if_t<std::is_pointer<T>::value, T> toPtr() const {
+  template <typename T, typename WrapFn = defaultWrap<T>>
+  std::enable_if_t<std::is_pointer<T>::value, T>
+  toPtr(WrapFn &&Wrap = WrapFn()) const {
     uintptr_t IntPtr = static_cast<uintptr_t>(Addr);
     assert(IntPtr == Addr && "ExecutorAddr value out of range for uintptr_t");
-    return reinterpret_cast<T>(IntPtr);
+    return Wrap(reinterpret_cast<T>(IntPtr));
   }
 
   /// Cast this ExecutorAddr to a pointer of the given function type.
   /// Warning: This should only be used when JITing in-process.
-  template <typename T>
-  std::enable_if_t<std::is_function<T>::value, T *> toPtr() const {
+  template <typename T, typename WrapFn = defaultWrap<T *>>
+  std::enable_if_t<std::is_function<T>::value, T *>
+  toPtr(WrapFn &&Wrap = WrapFn()) const {
     uintptr_t IntPtr = static_cast<uintptr_t>(Addr);
     assert(IntPtr == Addr && "ExecutorAddr value out of range for uintptr_t");
-    return reinterpret_cast<T *>(IntPtr);
+    return Wrap(reinterpret_cast<T *>(IntPtr));
   }
 
   uint64_t getValue() const { return Addr; }

llvm/unittests/ExecutionEngine/Orc/ExecutorAddressTest.cpp

@@ -58,6 +58,26 @@ TEST(ExecutorAddrTest, PtrConversionWithFunctionType) {
   EXPECT_EQ(FPtr, &F);
 }
 
+TEST(ExecutorAddrTest, WrappingAndUnwrapping) {
+  constexpr uintptr_t RawAddr = 0x123456;
+  int *RawPtr = (int *)RawAddr;
+
+  constexpr uintptr_t TagOffset = 8 * (sizeof(uintptr_t) - 1);
+  uintptr_t TagVal = 0xA5;
+  uintptr_t TagBits = TagVal << TagOffset;
+  void *TaggedPtr = (void *)((uintptr_t)RawPtr | TagBits);
+
+  ExecutorAddr EA =
+      ExecutorAddr::fromPtr(TaggedPtr, ExecutorAddr::Untag(8, TagOffset));
+
+  EXPECT_EQ(EA.getValue(), RawAddr);
+
+  void *ReconstitutedTaggedPtr =
+      EA.toPtr<void *>(ExecutorAddr::Tag(TagVal, TagOffset));
+
+  EXPECT_EQ(TaggedPtr, ReconstitutedTaggedPtr);
+}
+
 TEST(ExecutorAddrTest, AddrRanges) {
   ExecutorAddr A0(0), A1(1), A2(2), A3(3);
   ExecutorAddrRange R0(A0, A1), R1(A1, A2), R2(A2, A3), R3(A0, A2), R4(A1, A3);