3 files changed, 37 insertions, 0 deletions
diff --git a/include/llvm/ADT/APInt.h b/include/llvm/ADT/APInt.h
index d494ad2535..2073fa08cb 100644
--- a/include/llvm/ADT/APInt.h
+++ b/include/llvm/ADT/APInt.h
@@ -1244,6 +1244,9 @@ public:
   /// as "bitPosition".
   void flipBit(unsigned bitPosition);
 
+  /// \brief Returns true if the bit in bitPosition is set.
+  bool extractBit(unsigned bitPosition) const;
+
   /// @}
   /// \name Value Characterization Functions
   /// @{
diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index 89f96bd577..731c8cc9ca 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -607,6 +607,14 @@ void APInt::flipBit(unsigned bitPosition) {
   else setBit(bitPosition);
 }
 
+bool APInt::extractBit(unsigned bitPosition) const {
+  assert(bitPosition < BitWidth && "Out of the bit-width range!");
+  if (isSingleWord())
+    return VAL & maskBit(bitPosition);
+  else
+    return pVal[whichWord(bitPosition)] & maskBit(bitPosition);
+}
+
 unsigned APInt::getBitsNeeded(StringRef str, uint8_t radix) {
   assert(!str.empty() && "Invalid string length");
   assert((radix == 10 || radix == 8 || radix == 16 || radix == 2 || 
diff --git a/unittests/ADT/APIntTest.cpp b/unittests/ADT/APIntTest.cpp
index 3c0dfe1440..1d330f0d36 100644
--- a/unittests/ADT/APIntTest.cpp
+++ b/unittests/ADT/APIntTest.cpp
@@ -597,4 +597,30 @@ TEST(APIntTest, tcDecrement) {
     EXPECT_EQ(APInt::tcCompare(test, expected, 4), 0);
   }
 }
+
+TEST(APIntTest, extractBit) {
+  // Single word check.
+  uint64_t E1 = 0x2CA7F46BF6569915ULL;
+  APInt A1(64, E1);
+  for (unsigned i = 0, e = 64; i < e; ++i) {    
+    EXPECT_EQ(bool(E1 & (1ULL << i)),
+              A1.extractBit(i));
+  }
+
+  // Multiword check.
+  integerPart E2[4] = {
+    0xeb6eb136591cba21ULL,
+    0x7b9358bd6a33f10aULL,
+    0x7e7ffa5eadd8846ULL,
+    0x305f341ca00b613dULL
+  };
+  APInt A2(integerPartWidth*4, ArrayRef<integerPart>(E2, 4));
+  for (unsigned i = 0; i < 4; ++i) {
+    for (unsigned j = 0; j < integerPartWidth; ++j) {
+      EXPECT_EQ(bool(E2[i] & (1ULL << j)),
+                A2.extractBit(i*integerPartWidth + j));
+    }
+  }
+}
+
 }