Simplify firstGeq - make it not stepwise

ConflictSet.cpp

@@ -1741,109 +1741,69 @@ void addWriteRange(Node *&root, int64_t oldestVersion,
   }
 }
 
-struct FirstGeqStepwise {
-  Node *n;
-  std::span<const uint8_t> remaining;
-  int cmp;
-
-  enum Phase {
-    Init,
-    // Being in this phase implies that the key matches the search path exactly
-    // up to this point
-    Search,
-    DownLeftSpine
-  };
-  Phase phase;
-
-  FirstGeqStepwise(Node *n, std::span<const uint8_t> remaining)
-      : n(n), remaining(remaining), phase(Init) {}
-
-  // Not being done implies that n is not the firstGeq
-  bool step() {
-    switch (phase) {
-    case Search: {
-      if (remaining.size() == 0) {
-        int c = getChildGeq(n, 0);
-        assert(c >= 0);
-        n = getChildExists(n, c);
-        return downLeftSpine();
+Iterator firstGeq(Node *n, const std::span<const uint8_t> key) {
+  auto remaining = key;
+  for (;;) {
+    if (remaining.size() == 0) {
+      if (n->entryPresent) {
+        return {n, 0};
       }
-
-      auto *child = getChild(n, remaining[0]);
-      if (child == nullptr) {
-        int c = getChildGeq(n, remaining[0]);
-        if (c >= 0) {
-          n = getChildExists(n, c);
-          return downLeftSpine();
-        } else {
-          n = nextSibling(n);
-          return downLeftSpine();
-        }
-      }
-
-      n = child;
-      remaining = remaining.subspan(1, remaining.size() - 1);
-
-      if (n->partialKeyLen > 0) {
-        int commonLen = std::min<int>(n->partialKeyLen, remaining.size());
-        int i = longestCommonPrefixPartialKey(n->partialKey, remaining.data(),
-                                              commonLen);
-        if (i < commonLen) {
-          auto c = n->partialKey[i] <=> remaining[i];
-          if (c > 0) {
-            return downLeftSpine();
-          } else {
-            n = nextSibling(n);
-            return downLeftSpine();
-          }
-        }
-        if (commonLen == n->partialKeyLen) {
-          // partial key matches
-          remaining =
-              remaining.subspan(commonLen, remaining.size() - commonLen);
-        } else if (n->partialKeyLen > int(remaining.size())) {
-          // n is the first physical node greater than remaining, and there's no
-          // eq node
-          return downLeftSpine();
-        }
-      }
-    }
-      [[fallthrough]];
-    case Init:
-      phase = Search;
-      if (remaining.size() == 0 && n->entryPresent) {
-        cmp = 0;
-        return true;
-      }
-      return false;
-    case DownLeftSpine:
       int c = getChildGeq(n, 0);
       assert(c >= 0);
       n = getChildExists(n, c);
-      if (n->entryPresent) {
-        cmp = 1;
-        return true;
+      goto downLeftSpine;
+    }
+
+    auto *child = getChild(n, remaining[0]);
+    if (child == nullptr) {
+      int c = getChildGeq(n, remaining[0]);
+      if (c >= 0) {
+        n = getChildExists(n, c);
+        goto downLeftSpine;
+      } else {
+        n = nextSibling(n);
+        goto downLeftSpine;
       }
-      return false;
     }
-    __builtin_unreachable(); // GCOVR_EXCL_LINE
-  }
 
-  bool downLeftSpine() {
-    phase = DownLeftSpine;
-    if (n == nullptr || n->entryPresent) {
-      cmp = 1;
-      return true;
+    n = child;
+    remaining = remaining.subspan(1, remaining.size() - 1);
+
+    if (n->partialKeyLen > 0) {
+      int commonLen = std::min<int>(n->partialKeyLen, remaining.size());
+      int i = longestCommonPrefixPartialKey(n->partialKey, remaining.data(),
+                                            commonLen);
+      if (i < commonLen) {
+        auto c = n->partialKey[i] <=> remaining[i];
+        if (c > 0) {
+          goto downLeftSpine;
+        } else {
+          n = nextSibling(n);
+          goto downLeftSpine;
+        }
+      }
+      if (commonLen == n->partialKeyLen) {
+        // partial key matches
+        remaining = remaining.subspan(commonLen, remaining.size() - commonLen);
+      } else if (n->partialKeyLen > int(remaining.size())) {
+        // n is the first physical node greater than remaining, and there's no
+        // eq node
+        goto downLeftSpine;
+      }
     }
-    return step();
   }
-};
-
-Iterator firstGeq(Node *n, const std::span<const uint8_t> key) {
-  FirstGeqStepwise stepwise{n, key};
-  while (!stepwise.step())
-    ;
-  return {stepwise.n, stepwise.cmp};
+downLeftSpine:
+  if (n == nullptr) {
+    return {nullptr, 1};
+  }
+  for (;;) {
+    if (n->entryPresent) {
+      return {n, 1};
+    }
+    int c = getChildGeq(n, 0);
+    assert(c >= 0);
+    n = getChildExists(n, c);
+  }
 }
 
 struct __attribute__((visibility("hidden"))) ConflictSet::Impl {