Add portable bit mask operations to BitVector.

BitVector uses the native word size for its internal representation.
That doesn't work well for literal bit masks in source code.

This patch adds BitVector operations to efficiently apply literal bit
masks specified as arrays of uint32_t.  Since each array entry always
holds exactly 32 bits, these portable bit masks can be source code
literals, probably produced by TableGen.

llvm-svn: 148272

2 files changed, 109 insertions, 0 deletions

diff --git a/llvm/include/llvm/ADT/BitVector.h b/llvm/include/llvm/ADT/BitVector.h
index ac1cf0c79a8..7d7afc347eb 100644
--- a/llvm/include/llvm/ADT/BitVector.h
+++ b/llvm/include/llvm/ADT/BitVector.h
@@ -365,6 +365,42 @@ public:
     std::swap(Capacity, RHS.Capacity);
   }
 
+  //===--------------------------------------------------------------------===//
+  // Portable bit mask operations.
+  //===--------------------------------------------------------------------===//
+  //
+  // These methods all operate on arrays of uint32_t, each holding 32 bits. The
+  // fixed word size makes it easier to work with literal bit vector constants
+  // in portable code.
+  //
+  // The LSB in each word is the lowest numbered bit.  The size of a portable
+  // bit mask is always a whole multiple of 32 bits.  If no bit mask size is
+  // given, the bit mask is assumed to cover the entire BitVector.
+
+  /// setBitsInMask - Add '1' bits from Mask to this vector. Don't resize.
+  /// This computes "*this |= Mask".
+  void setBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
+    applyMask<true, false>(Mask, MaskWords);
+  }
+
+  /// clearBitsInMask - Clear any bits in this vector that are set in Mask.
+  /// Don't resize. This computes "*this &= ~Mask".
+  void clearBitsInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
+    applyMask<false, false>(Mask, MaskWords);
+  }
+
+  /// setBitsNotInMask - Add a bit to this vector for every '0' bit in Mask.
+  /// Don't resize.  This computes "*this |= ~Mask".
+  void setBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
+    applyMask<true, true>(Mask, MaskWords);
+  }
+
+  /// clearBitsNotInMask - Clear a bit in this vector for every '0' bit in Mask.
+  /// Don't resize.  This computes "*this &= Mask".
+  void clearBitsNotInMask(const uint32_t *Mask, unsigned MaskWords = ~0u) {
+    applyMask<false, true>(Mask, MaskWords);
+  }
+
 private:
   unsigned NumBitWords(unsigned S) const {
     return (S + BITWORD_SIZE-1) / BITWORD_SIZE;
@@ -400,6 +436,33 @@ private:
   void init_words(BitWord *B, unsigned NumWords, bool t) {
     memset(B, 0 - (int)t, NumWords*sizeof(BitWord));
   }
+
+  template<bool AddBits, bool InvertMask>
+  void applyMask(const uint32_t *Mask, unsigned MaskWords) {
+    assert(BITWORD_SIZE % 32 == 0 && "Unsupported BitWord size.");
+    MaskWords = std::min(MaskWords, (size() + 31) / 32);
+    const unsigned Scale = BITWORD_SIZE / 32;
+    unsigned i;
+    for (i = 0; MaskWords >= Scale; ++i, MaskWords -= Scale) {
+      BitWord BW = Bits[i];
+      // This inner loop should unroll completely when BITWORD_SIZE > 32.
+      for (unsigned b = 0; b != BITWORD_SIZE; b += 32) {
+        uint32_t M = *Mask++;
+        if (InvertMask) M = ~M;
+        if (AddBits) BW |=   BitWord(M) << b;
+        else         BW &= ~(BitWord(M) << b);
+      }
+      Bits[i] = BW;
+    }
+    for (unsigned b = 0; MaskWords; b += 32, --MaskWords) {
+      uint32_t M = *Mask++;
+      if (InvertMask) M = ~M;
+      if (AddBits) Bits[i] |=   BitWord(M) << b;
+      else         Bits[i] &= ~(BitWord(M) << b);
+    }
+    if (AddBits)
+      clear_unused_bits();
+  }
 };
 
 inline BitVector operator&(const BitVector &LHS, const BitVector &RHS) {
diff --git a/llvm/unittests/ADT/BitVectorTest.cpp b/llvm/unittests/ADT/BitVectorTest.cpp
index fa663121a8a..f733e13fdfc 100644
--- a/llvm/unittests/ADT/BitVectorTest.cpp
+++ b/llvm/unittests/ADT/BitVectorTest.cpp
@@ -196,6 +196,52 @@ TEST(BitVectorTest, ProxyIndex) {
   EXPECT_TRUE(Vec.none());
 }
 
+TEST(BitVectorTest, PortableBitMask) {
+  BitVector A;
+  const uint32_t Mask1[] = { 0x80000000, 6, 5 };
+
+  A.resize(10);
+  A.setBitsInMask(Mask1, 3);
+  EXPECT_EQ(10u, A.size());
+  EXPECT_FALSE(A.test(0));
+
+  A.resize(32);
+  A.setBitsInMask(Mask1, 3);
+  EXPECT_FALSE(A.test(0));
+  EXPECT_TRUE(A.test(31));
+  EXPECT_EQ(1u, A.count());
+
+  A.resize(33);
+  A.setBitsInMask(Mask1, 1);
+  EXPECT_EQ(1u, A.count());
+  A.setBitsInMask(Mask1, 2);
+  EXPECT_EQ(1u, A.count());
+
+  A.resize(34);
+  A.setBitsInMask(Mask1, 2);
+  EXPECT_EQ(2u, A.count());
+
+  A.resize(65);
+  A.setBitsInMask(Mask1, 3);
+  EXPECT_EQ(4u, A.count());
+
+  A.setBitsNotInMask(Mask1, 1);
+  EXPECT_EQ(32u+3u, A.count());
+
+  A.setBitsNotInMask(Mask1, 3);
+  EXPECT_EQ(65u, A.count());
+
+  A.resize(96);
+  EXPECT_EQ(65u, A.count());
+
+  A.clear();
+  A.resize(128);
+  A.setBitsNotInMask(Mask1, 3);
+  EXPECT_EQ(96u-5u, A.count());
+
+  A.clearBitsNotInMask(Mask1, 1);
+  EXPECT_EQ(64-4u, A.count());
+}
 }
 
 #endif