radix: Let the compiler inline and deduplicate radix{_range}.end()

This puts the trivial part of the radix_iterator constructor used by end() in the class definition, so the compiler can see the full definition of end(). This should let it inline it and, hopefully, constant-eliminate it so it doesn't get called repeatedly.

radix: Let the compiler inline and deduplicate radix{_range}.end()
73eaacd0 · Austin Clements · 53ec8ed9 · 73eaacd0 · 73eaacd0
--- a/include/radix.hh
+++ b/include/radix.hh
@@ -234,7 +234,12 @@ struct radix_iterator {
  // The level of the current element.
  u32 level_;
-  radix_iterator(const radix* r, u64 k, u64 limit);
+  radix_iterator(const radix* r, u64 k, u64 limit)
+    : r_(r), k_(k), key_limit_(limit)
+  {
+    if (k_ != key_limit_)
+      prime_path();
+  }
  radix_iterator &operator++() {
    assert(k_ < key_limit_);
@@ -252,6 +257,8 @@ struct radix_iterator {
    return r_ != other.r_ || k_ != other.k_; }
 private:
+  // Prepare the initial path_ and level_ based on k_.
+  void prime_path();
  // Advance to the next non-null leaf.  This assumes that
  // k_ < key_limit_.
  void advance();

--- a/kernel/radix.cc
+++ b/kernel/radix.cc
@@ -246,11 +246,10 @@ radix_range::replace(u64 start, u64 size, radix_elem *val)
    }, 0, 1L << key_bits, start, start + size);
 }
-radix_iterator::radix_iterator(const radix* r, u64 k, u64 limit)
+void
-  : r_(r), k_(k), key_limit_(limit) {
+radix_iterator::prime_path()
+{
  dprintf("%p: Made iterator with k = %lx\n", r_, k_);
-  if (k_ == key_limit_)
-    return;
  // Load the initial path
  level_ = radix_levels;
@@ -261,6 +260,7 @@ radix_iterator::radix_iterator(const radix* r, u64 k, u64 limit)
    path_[level_] = &entry.node()->child[index(k_, level_)];
    node = path_[level_];
  }
  dprintf("%p: Adjusted: k = %lx\n", r_, k_);
 }