Fix crash when SimdComparison calls SIMD instructions (#8820)

Summary:
Fixes #8668

Pull Request resolved: #8820

Reviewed By: Yuhta

Differential Revision: D54454632

Pulled By: kgpai

fbshipit-source-id: 08f6f98f151c2a7c2b80f6b414159ce49a52faca

velox/functions/prestosql/Comparisons.cpp

@@ -52,7 +52,7 @@ struct SimdComparator {
     if constexpr (numScalarElements == 2 || numScalarElements == 4) {
       for (auto i = begin; i < vectorEnd; i += 8) {
         rawResult[i / 8] = 0;
-        for (auto j = 0; j < 8 && j < vectorEnd; j += numScalarElements) {
+        for (auto j = 0; j < 8 && (i + j) < vectorEnd; j += numScalarElements) {
           auto left = loadSimdData<T, isLeftConstant>(rawLhs, i + j);
           auto right = loadSimdData<T, isRightConstant>(rawRhs, i + j);
 

velox/functions/prestosql/tests/ComparisonsTest.cpp

@@ -601,6 +601,40 @@ TEST_F(ComparisonsTest, eqNestedComplex) {
   }
 }
 
+TEST_F(ComparisonsTest, overflowTest) {
+  auto makeFlatVector = [&](size_t numRows, size_t delta) {
+    BufferPtr values =
+        AlignedBuffer::allocate<int64_t>(numRows + delta, pool());
+    auto rawValues = values->asMutable<int64_t>();
+    for (size_t i = 0; i < numRows + delta; ++i) {
+      rawValues[i] = i;
+    }
+    return std::make_shared<FlatVector<int64_t>>(
+        pool(), BIGINT(), nullptr, numRows, values, std::vector<BufferPtr>{});
+  };
+
+  size_t numRows = 1006;
+  size_t delta = 2;
+  auto rowVector = makeRowVector(
+      {makeFlatVector(numRows, delta), makeFlatVector(numRows, delta)});
+  auto result =
+      evaluate<SimpleVector<bool>>(fmt::format("{}(c0, c1)", "eq"), rowVector);
+  for (auto i = 0; i < result->size(); ++i) {
+    ASSERT_TRUE(result->valueAt(i));
+  }
+
+  auto flatResult = result->asFlatVector<bool>();
+  auto rawResult = flatResult->mutableRawValues();
+  for (auto i = 0; i < result->size(); ++i) {
+    ASSERT_TRUE(
+        bits::isBitSet(reinterpret_cast<const uint64_t*>(rawResult), i));
+  }
+  for (auto i = result->size(); i < result->size() + delta; ++i) {
+    ASSERT_FALSE(
+        bits::isBitSet(reinterpret_cast<const uint64_t*>(rawResult), i));
+  }
+}
+
 namespace {
 template <typename Tp, typename Op, const char* fnName>
 struct ComparisonTypeOp {