[llvm] a8e5dcb - Fix bug in SmallBitVector::find_next_unset

[David Blaikie via llvm-commits]

Author: David Blaikie
Date: 2020-04-24T13:50:30-07:00
New Revision: a8e5dcb072b1f794883ae8125fb08c06db678d56

URL: https://github.com/llvm/llvm-project/commit/a8e5dcb072b1f794883ae8125fb08c06db678d56
DIFF: https://github.com/llvm/llvm-project/commit/a8e5dcb072b1f794883ae8125fb08c06db678d56.diff

LOG: Fix bug in SmallBitVector::find_next_unset

Summary: find_next_unset was returning size() instead of -1 in small-mode, when no unset bits are found.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D77985

Added: 
    

Modified: 
    llvm/include/llvm/ADT/SmallBitVector.h
    llvm/unittests/ADT/BitVectorTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/SmallBitVector.h b/llvm/include/llvm/ADT/SmallBitVector.h
index 14545e2b612d..f570bac23ad5 100644
--- a/llvm/include/llvm/ADT/SmallBitVector.h
+++ b/llvm/include/llvm/ADT/SmallBitVector.h
@@ -287,11 +287,11 @@ class SmallBitVector {
   /// Returns -1 if the next unset bit is not found.
   int find_next_unset(unsigned Prev) const {
     if (isSmall()) {
-      ++Prev;
       uintptr_t Bits = getSmallBits();
       // Mask in previous bits.
-      uintptr_t Mask = (uintptr_t(1) << Prev) - 1;
-      Bits |= Mask;
+      Bits |= (uintptr_t(1) << (Prev + 1)) - 1;
+      // Mask in unused bits.
+      Bits |= ~uintptr_t(0) << getSmallSize();
 
       if (Bits == ~uintptr_t(0) || Prev + 1 >= getSmallSize())
         return -1;

diff  --git a/llvm/unittests/ADT/BitVectorTest.cpp b/llvm/unittests/ADT/BitVectorTest.cpp
index efefd2b90be8..0f15a478e452 100644
--- a/llvm/unittests/ADT/BitVectorTest.cpp
+++ b/llvm/unittests/ADT/BitVectorTest.cpp
@@ -297,6 +297,18 @@ TYPED_TEST(BitVectorTest, SimpleFindOpsSingleWord) {
   EXPECT_EQ(-1, A.find_last_unset());
 
   A.resize(20);
+  ASSERT_TRUE(SmallBitVectorIsSmallMode(A));
+  EXPECT_EQ(-1, A.find_first());
+  EXPECT_EQ(-1, A.find_last());
+  EXPECT_EQ(-1, A.find_next(5));
+  EXPECT_EQ(-1, A.find_next(19));
+  EXPECT_EQ(-1, A.find_prev(5));
+  EXPECT_EQ(-1, A.find_prev(20));
+  EXPECT_EQ(0, A.find_first_unset());
+  EXPECT_EQ(19, A.find_last_unset());
+  EXPECT_EQ(6, A.find_next_unset(5));
+  EXPECT_EQ(-1, A.find_next_unset(19));
+
   A.set(3);
   A.set(4);
   A.set(16);
@@ -319,6 +331,19 @@ TYPED_TEST(BitVectorTest, SimpleFindOpsSingleWord) {
   EXPECT_EQ(5, A.find_next_unset(4));
   EXPECT_EQ(13, A.find_next_unset(12));
   EXPECT_EQ(17, A.find_next_unset(15));
+
+  A.set();
+  ASSERT_TRUE(SmallBitVectorIsSmallMode(A));
+  EXPECT_EQ(0, A.find_first());
+  EXPECT_EQ(19, A.find_last());
+  EXPECT_EQ(6, A.find_next(5));
+  EXPECT_EQ(-1, A.find_next(19));
+  EXPECT_EQ(4, A.find_prev(5));
+  EXPECT_EQ(19, A.find_prev(20));
+  EXPECT_EQ(-1, A.find_first_unset());
+  EXPECT_EQ(-1, A.find_last_unset());
+  EXPECT_EQ(-1, A.find_next_unset(5));
+  EXPECT_EQ(-1, A.find_next_unset(19));
 }
 
 TEST(BitVectorTest, FindInRangeMultiWord) {