Add getFirstChildExists

ConflictSet.cpp

@@ -1029,6 +1029,43 @@ int getChildGeq(Node *self, int child) {
   }
 }
 
+// Precondition: self has a child
+Node *getFirstChildExists(Node3 *self) {
+  assert(self->numChildren > 0);
+  return self->children[0];
+}
+// Precondition: self has a child
+Node *getFirstChildExists(Node16 *self) {
+  assert(self->numChildren > 0);
+  return self->children[0];
+}
+// Precondition: self has a child
+Node *getFirstChildExists(Node48 *self) {
+  return self->children[self->index[self->bitSet.firstSetGeq(0)]];
+}
+// Precondition: self has a child
+Node *getFirstChildExists(Node256 *self) {
+  return self->children[self->bitSet.firstSetGeq(0)];
+}
+
+// Precondition: self has a child
+Node *getFirstChildExists(Node *self) {
+  switch (self->getType()) {
+  case Type_Node0:           // GCOVR_EXCL_LINE
+    __builtin_unreachable(); // GCOVR_EXCL_LINE
+  case Type_Node3:
+    return getFirstChildExists(static_cast<Node3 *>(self));
+  case Type_Node16:
+    return getFirstChildExists(static_cast<Node16 *>(self));
+  case Type_Node48:
+    return getFirstChildExists(static_cast<Node48 *>(self));
+  case Type_Node256:
+    return getFirstChildExists(static_cast<Node256 *>(self));
+  default:                   // GCOVR_EXCL_LINE
+    __builtin_unreachable(); // GCOVR_EXCL_LINE
+  }
+}
+
 // Caller is responsible for assigning a non-null pointer to the returned
 // reference if null
 Node *&getOrCreateChild(Node *&self, uint8_t index, WriteContext *tls) {
@@ -1900,14 +1937,9 @@ bool checkPointRead(Node *n, const std::span<const uint8_t> key,
     }
   }
 downLeftSpine:
-  for (;;) {
-    if (n->entryPresent) {
-      return n->entry.rangeVersion <= readVersion;
-    }
-    int c = getChildGeq(n, 0);
-    assert(c >= 0);
-    n = getChildExists(n, c);
+  for (; !n->entryPresent; n = getFirstChildExists(n)) {
   }
+  return n->entry.rangeVersion <= readVersion;
 }
 
 // Logically this is the same as performing firstGeq and then checking against
@@ -1980,14 +2012,9 @@ bool checkPrefixRead(Node *n, const std::span<const uint8_t> key,
     }
   }
 downLeftSpine:
-  for (;;) {
-    if (n->entryPresent) {
-      return n->entry.rangeVersion <= readVersion;
-    }
-    int c = getChildGeq(n, 0);
-    assert(c >= 0);
-    n = getChildExists(n, c);
+  for (; !n->entryPresent; n = getFirstChildExists(n)) {
   }
+  return n->entry.rangeVersion <= readVersion;
 }
 
 #ifdef HAS_AVX