[llvm] r203273 - [ADT] Update PointerIntPair to handle pointer types with more than 31 bits free.

[Jordan Rose]

Author: jrose
Date: Fri Mar  7 13:19:56 2014
New Revision: 203273

URL: http://llvm.org/viewvc/llvm-project?rev=203273&view=rev
Log:
[ADT] Update PointerIntPair to handle pointer types with more than 31 bits free.

Previously, the assertions in PointerIntPair would try to calculate the value
(1 << NumLowBitsAvailable); the inferred type here is 'int', so if there were
more than 31 bits available we'd get a shift overflow.

Also, add a rudimentary unit test file for PointerIntPair.

Added:
    llvm/trunk/unittests/ADT/PointerIntPairTest.cpp
Modified:
    llvm/trunk/include/llvm/ADT/PointerIntPair.h
    llvm/trunk/unittests/ADT/CMakeLists.txt

Modified: llvm/trunk/include/llvm/ADT/PointerIntPair.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/PointerIntPair.h?rev=203273&r1=203272&r2=203273&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/PointerIntPair.h (original)
+++ llvm/trunk/include/llvm/ADT/PointerIntPair.h Fri Mar  7 13:19:56 2014
@@ -17,6 +17,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/PointerLikeTypeTraits.h"
 #include <cassert>
+#include <limits>
 
 namespace llvm {
 
@@ -41,6 +42,9 @@ template <typename PointerTy, unsigned I
           typename PtrTraits = PointerLikeTypeTraits<PointerTy> >
 class PointerIntPair {
   intptr_t Value;
+  static_assert(PtrTraits::NumLowBitsAvailable <
+                std::numeric_limits<uintptr_t>::digits,
+                "cannot use a pointer type that has all bits free");
   enum : uintptr_t {
     /// PointerBitMask - The bits that come from the pointer.
     PointerBitMask =
@@ -79,7 +83,7 @@ public:
   void setPointer(PointerTy PtrVal) {
     intptr_t PtrWord
       = reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
-    assert((PtrWord & ((1 << PtrTraits::NumLowBitsAvailable)-1)) == 0 &&
+    assert((PtrWord & ~PointerBitMask) == 0 &&
            "Pointer is not sufficiently aligned");
     // Preserve all low bits, just update the pointer.
     Value = PtrWord | (Value & ~PointerBitMask);
@@ -87,7 +91,7 @@ public:
 
   void setInt(IntType IntVal) {
     intptr_t IntWord = static_cast<intptr_t>(IntVal);
-    assert(IntWord < (1 << IntBits) && "Integer too large for field");
+    assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
     
     // Preserve all bits other than the ones we are updating.
     Value &= ~ShiftedIntMask;     // Remove integer field.
@@ -97,7 +101,7 @@ public:
   void initWithPointer(PointerTy PtrVal) {
     intptr_t PtrWord
       = reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
-    assert((PtrWord & ((1 << PtrTraits::NumLowBitsAvailable)-1)) == 0 &&
+    assert((PtrWord & ~PointerBitMask) == 0 &&
            "Pointer is not sufficiently aligned");
     Value = PtrWord;
   }
@@ -105,10 +109,10 @@ public:
   void setPointerAndInt(PointerTy PtrVal, IntType IntVal) {
     intptr_t PtrWord
       = reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(PtrVal));
-    assert((PtrWord & ((1 << PtrTraits::NumLowBitsAvailable)-1)) == 0 &&
+    assert((PtrWord & ~PointerBitMask) == 0 &&
            "Pointer is not sufficiently aligned");
     intptr_t IntWord = static_cast<intptr_t>(IntVal);
-    assert(IntWord < (1 << IntBits) && "Integer too large for field");
+    assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
 
     Value = PtrWord | (IntWord << IntShift);
   }

Modified: llvm/trunk/unittests/ADT/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/CMakeLists.txt?rev=203273&r1=203272&r2=203273&view=diff
==============================================================================
--- llvm/trunk/unittests/ADT/CMakeLists.txt (original)
+++ llvm/trunk/unittests/ADT/CMakeLists.txt Fri Mar  7 13:19:56 2014
@@ -24,6 +24,7 @@ set(ADTSources
   OptionalTest.cpp
   OwningPtrTest.cpp
   PackedVectorTest.cpp
+  PointerIntPairTest.cpp
   PointerUnionTest.cpp
   SCCIteratorTest.cpp
   SmallPtrSetTest.cpp

Added: llvm/trunk/unittests/ADT/PointerIntPairTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/ADT/PointerIntPairTest.cpp?rev=203273&view=auto
==============================================================================
--- llvm/trunk/unittests/ADT/PointerIntPairTest.cpp (added)
+++ llvm/trunk/unittests/ADT/PointerIntPairTest.cpp Fri Mar  7 13:19:56 2014
@@ -0,0 +1,74 @@
+//===- llvm/unittest/ADT/PointerIntPairTest.cpp - Unit tests --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "gtest/gtest.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include <limits>
+using namespace llvm;
+
+namespace {
+
+// Test fixture
+class PointerIntPairTest : public testing::Test {
+};
+
+TEST_F(PointerIntPairTest, GetSet) {
+  PointerIntPair<PointerIntPairTest *, 2> Pair{this, 1U};
+  EXPECT_EQ(this, Pair.getPointer());
+  EXPECT_EQ(1U, Pair.getInt());
+
+  Pair.setInt(2);
+  EXPECT_EQ(this, Pair.getPointer());
+  EXPECT_EQ(2U, Pair.getInt());
+
+  Pair.setPointer(nullptr);
+  EXPECT_EQ(nullptr, Pair.getPointer());
+  EXPECT_EQ(2U, Pair.getInt());
+
+  Pair.setPointerAndInt(this, 3U);
+  EXPECT_EQ(this, Pair.getPointer());
+  EXPECT_EQ(3U, Pair.getInt());
+}
+
+TEST_F(PointerIntPairTest, DefaultInitialize) {
+  PointerIntPair<PointerIntPairTest *, 2> Pair;
+  EXPECT_EQ(nullptr, Pair.getPointer());
+  EXPECT_EQ(0U, Pair.getInt());
+}
+
+TEST_F(PointerIntPairTest, ManyUnusedBits) {
+  // In real code this would be a word-sized integer limited to 31 bits.
+  struct Fixnum31 {
+    uintptr_t Value;
+  };
+  class FixnumPointerTraits {
+  public:
+    static inline void *getAsVoidPointer(Fixnum31 Num) {
+      return reinterpret_cast<void *>(Num.Value << NumLowBitsAvailable);
+    }
+    static inline Fixnum31 getFromVoidPointer(void *P) {
+      // In real code this would assert that the value is in range.
+      return { reinterpret_cast<uintptr_t>(P) >> NumLowBitsAvailable };
+    }
+    enum { NumLowBitsAvailable = std::numeric_limits<uintptr_t>::digits - 31 };
+  };
+
+  PointerIntPair<Fixnum31, 1, bool, FixnumPointerTraits> pair;
+  EXPECT_EQ((uintptr_t)0, pair.getPointer().Value);
+  EXPECT_EQ(false, pair.getInt());
+
+  pair.setPointerAndInt({ 0x7FFFFFFF }, true );
+  EXPECT_EQ((uintptr_t)0x7FFFFFFF, pair.getPointer().Value);
+  EXPECT_EQ(true, pair.getInt());
+
+  EXPECT_EQ(FixnumPointerTraits::NumLowBitsAvailable - 1,
+            PointerLikeTypeTraits<decltype(pair)>::NumLowBitsAvailable);
+}
+
+} // end anonymous namespace