Merge pull request #27187 from vespa-engine/balder/use-static-assert-for-idx

replace runtime assert with a static assert, and also optimize incIdx…

2 files changed, 8 insertions, 13 deletions

diff --git a/vespalib/src/vespa/vespalib/btree/btreeiterator.h b/vespalib/src/vespa/vespalib/btree/btreeiterator.h
index 14143836c22..7ab28c9b5c9 100644
--- a/vespalib/src/vespa/vespalib/btree/btreeiterator.h
+++ b/vespalib/src/vespa/vespalib/btree/btreeiterator.h
@@ -43,12 +43,13 @@ class NodeElement
     static constexpr uint64_t NODE_MASK = (1ul << NODE_BITS) - 1ul;
     static constexpr uint64_t IDX_MASK = (1ul << IDX_BITS) - 1ul;
     static constexpr uint8_t IDX_SHIFT = NODE_BITS;
+    static constexpr uint64_t IDX_ONE = 1ul << NODE_BITS;
 
+    static_assert((NodeType::maxSlots() + 1) < (1ul << IDX_BITS), "IDX can be out of bounds above 127");
 public:
     NodeElement() noexcept : _nodeAndIdx(0ul) { }
     NodeElement(const NodeType *node, uint32_t idx) noexcept : _nodeAndIdx(uint64_t(node) | uint64_t(idx) << IDX_SHIFT) {
         assert((uint64_t(node) & ~NODE_MASK) == 0ul);
-        assert(idx <= IDX_MASK);
     }
 
     void invalidate() noexcept { _nodeAndIdx = 0; }
@@ -58,16 +59,14 @@ public:
     }
     const NodeType * getNode() const noexcept { return reinterpret_cast<const NodeType *>(_nodeAndIdx & NODE_MASK); }
     void setIdx(uint32_t idx) noexcept {
-        assert(idx <= IDX_MASK);
         _nodeAndIdx = (_nodeAndIdx & NODE_MASK) | (uint64_t(idx) << IDX_SHIFT);
     }
     uint32_t getIdx() const noexcept { return _nodeAndIdx >> IDX_SHIFT; }
-    void incIdx() noexcept { setIdx(getIdx() + 1); }
-    void decIdx() noexcept { setIdx(getIdx() - 1); }
+    void incIdx() noexcept { _nodeAndIdx += IDX_ONE; }
+    void decIdx() noexcept { _nodeAndIdx -= IDX_ONE; }
 
     void setNodeAndIdx(const NodeType *node, uint32_t idx) noexcept {
         assert((uint64_t(node) & ~NODE_MASK) == 0ul);
-        assert(idx <= IDX_MASK);
         _nodeAndIdx = uint64_t(node) | uint64_t(idx) << IDX_SHIFT;
     }
 
@@ -119,9 +118,7 @@ template <typename KeyT,
 class BTreeIteratorBase
 {
 protected:
-    using NodeAllocatorType = BTreeNodeAllocator<KeyT, DataT, AggrT,
-                                                 INTERNAL_SLOTS,
-                                                 LEAF_SLOTS>;
+    using NodeAllocatorType = BTreeNodeAllocator<KeyT, DataT, AggrT, INTERNAL_SLOTS, LEAF_SLOTS>;
     using InternalNodeType = BTreeInternalNode<KeyT, AggrT, INTERNAL_SLOTS>;
     using LeafNodeType = BTreeLeafNode<KeyT, DataT, AggrT, LEAF_SLOTS> ;
     using InternalNodeTypeRefPair = typename InternalNodeType::RefPair;
@@ -161,7 +158,6 @@ protected:
 
     // Temporary leaf node when iterating over short arrays
     std::unique_ptr<LeafNodeTempType> _compatLeafNode;
-
 private:
     /*
      * Find the next leaf node, called by operator++() as needed.
diff --git a/vespalib/src/vespa/vespalib/btree/btreenode.h b/vespalib/src/vespa/vespalib/btree/btreenode.h
index cda088556de..0a77a0b4685 100644
--- a/vespalib/src/vespa/vespalib/btree/btreenode.h
+++ b/vespalib/src/vespa/vespalib/btree/btreenode.h
@@ -226,8 +226,8 @@ public:
 
     bool isFull() const noexcept { return validSlots() == NumSlots; }
     bool isAtLeastHalfFull() const noexcept { return validSlots() >= minSlots(); }
-    static uint32_t maxSlots() noexcept { return NumSlots; }
-    static uint32_t minSlots() noexcept { return NumSlots / 2; }
+    static constexpr uint32_t maxSlots() noexcept { return NumSlots; }
+    static constexpr uint32_t minSlots() noexcept { return NumSlots / 2; }
 };
 
 template <typename KeyT, typename DataT, typename AggrT, uint32_t NumSlots>
@@ -430,8 +430,7 @@ public:
     }
 };
 
-template <typename KeyT, typename DataT, typename AggrT,
-          uint32_t NumSlots = 16>
+template <typename KeyT, typename DataT, typename AggrT, uint32_t NumSlots = 16>
 class BTreeLeafNode : public BTreeNodeTT<KeyT, DataT, AggrT, NumSlots>
 {
 public: