diff --git a/runtime/memory_region.h b/runtime/memory_region.h
index fe3f917..f55dff7 100644
--- a/runtime/memory_region.h
+++ b/runtime/memory_region.h
@@ -124,11 +124,35 @@
   // The bit at the smallest offset is the least significant bit in the
   // loaded value.  `length` must not be larger than the number of bits
   // contained in the return value (32).
-  uint32_t LoadBits(uintptr_t bit_offset, size_t length) const {
-    CHECK_LE(length, sizeof(uint32_t) * kBitsPerByte);
-    uint32_t value = 0u;
+  ALWAYS_INLINE uint32_t LoadBits(uintptr_t bit_offset, size_t length) const {
+    DCHECK_LE(length, BitSizeOf<uint32_t>());
+    DCHECK_LE(bit_offset + length, size_in_bits());
+    if (UNLIKELY(length == 0)) {
+      // Do not touch any memory if the range is empty.
+      return 0;
+    }
+    const uint8_t* address = start() + bit_offset / kBitsPerByte;
+    const uint32_t shift = bit_offset & (kBitsPerByte - 1);
+    // Load the value (reading only the strictly needed bytes).
+    const uint32_t load_bit_count = shift + length;
+    uint32_t value = address[0] >> shift;
+    if (load_bit_count > 8) {
+      value |= static_cast<uint32_t>(address[1]) << (8 - shift);
+      if (load_bit_count > 16) {
+        value |= static_cast<uint32_t>(address[2]) << (16 - shift);
+        if (load_bit_count > 24) {
+          value |= static_cast<uint32_t>(address[3]) << (24 - shift);
+          if (load_bit_count > 32) {
+            value |= static_cast<uint32_t>(address[4]) << (32 - shift);
+          }
+        }
+      }
+    }
+    // Clear unwanted most significant bits.
+    uint32_t clear_bit_count = BitSizeOf(value) - length;
+    value = (value << clear_bit_count) >> clear_bit_count;
     for (size_t i = 0; i < length; ++i) {
-      value |= LoadBit(bit_offset + i) << i;
+      DCHECK_EQ((value >> i) & 1, LoadBit(bit_offset + i));
     }
     return value;
   }
@@ -137,13 +161,7 @@
   // `bit_offset`.  The bit at the smallest offset is the least significant
   // bit of the stored `value`.  `value` must not be larger than `length`
   // bits.
-  void StoreBits(uintptr_t bit_offset, uint32_t value, size_t length) {
-    CHECK_LE(value, MaxInt<uint32_t>(length));
-    for (size_t i = 0; i < length; ++i) {
-      bool ith_bit = value & (1 << i);
-      StoreBit(bit_offset + i, ith_bit);
-    }
-  }
+  void StoreBits(uintptr_t bit_offset, uint32_t value, size_t length);
 
   void CopyFrom(size_t offset, const MemoryRegion& from) const;