From 8bac1f66fcf5067f043435261dce5c81b30cc7c9 Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Sat, 12 Oct 2024 11:12:12 -0700
Subject: [PATCH] Remove searchPathLen

---
 ConflictSet.cpp | 51 ++++++++++++++++++++-----------------------------
 1 file changed, 21 insertions(+), 30 deletions(-)

diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 877cfd4..ef5b43f 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -2937,8 +2937,6 @@ struct CheckJob {
   std::span<const uint8_t> remaining; // range read only
   Node *child;                        // range read only
   int lcp;                            // range read only
-  int prefixLen;                      // range read only
-  int searchPathLen;                  // range read only
   Node *commonPrefixNode;             // range read only
   InternalVersionT readVersion;
   ConflictSet::Result *result;
@@ -3263,16 +3261,21 @@ static Continuation commonPrefixIterTable[] = {
     common_prefix_iter<Node16>, common_prefix_iter<Node48>,
     common_prefix_iter<Node256>};
 
-template <class NodeT>
+template <class NodeT, bool kFirst>
 PRESERVE_NONE void left_side_iter(CheckJob *, CheckContext *);
 
 PRESERVE_NONE void left_side_down_left_spine(CheckJob *, CheckContext *);
 
 PRESERVE_NONE void done_left_side_iter(CheckJob *, CheckContext *);
 
-static Continuation leftSideIterTable[] = {
-    left_side_iter<Node0>, left_side_iter<Node3>, left_side_iter<Node16>,
-    left_side_iter<Node48>, left_side_iter<Node256>};
+static Continuation leftSideIterTable[2][5] = {
+    {left_side_iter<Node0, false>, left_side_iter<Node3, false>,
+     left_side_iter<Node16, false>, left_side_iter<Node48, false>,
+     left_side_iter<Node256, false>},
+    {left_side_iter<Node0, true>, left_side_iter<Node3, true>,
+     left_side_iter<Node16, true>, left_side_iter<Node48, true>,
+     left_side_iter<Node256, true>},
+};
 
 PRESERVE_NONE void begin(CheckJob *job, CheckContext *context) {
   job->lcp = longestCommonPrefix(job->begin.data(), job->end.data(),
@@ -3381,8 +3384,6 @@ PRESERVE_NONE void done_common_prefix_iter(CheckJob *job,
   }
 
   job->remaining = job->begin;
-  job->searchPathLen = 0;
-  job->prefixLen = job->lcp + 1;
 
   auto c = getChild(job->n, job->remaining[0]);
   Node *child = c;
@@ -3406,32 +3407,32 @@ PRESERVE_NONE void done_common_prefix_iter(CheckJob *job,
   }
 
   job->n = child;
-  job->continuation = leftSideIterTable[c.getType()];
+  job->continuation = leftSideIterTable[true][c.getType()];
   __builtin_prefetch(job->n);
   MUSTTAIL return keepGoing(job, context);
 }
 
 // Return true if the max version among all keys that start with key[:prefixLen]
 // that are >= key is <= readVersion
-template <class NodeT>
+template <class NodeT, bool kFirst>
 PRESERVE_NONE void left_side_iter(CheckJob *job, CheckContext *context) {
   assert(NodeT::kType == job->n->getType());
   NodeT *n = static_cast<NodeT *>(job->n);
 
   job->remaining = job->remaining.subspan(1, job->remaining.size() - 1);
-  ++job->searchPathLen;
 
   if (n->partialKeyLen > 0) {
     int commonLen = std::min<int>(n->partialKeyLen, job->remaining.size());
     int i =
         longestCommonPrefix(n->partialKey(), job->remaining.data(), commonLen);
-    job->searchPathLen += i;
     if (i < commonLen) {
       auto c = n->partialKey()[i] <=> job->remaining[i];
       if (c > 0) {
-        if (job->searchPathLen < job->prefixLen) {
-          job->continuation = left_side_down_left_spine;
-          MUSTTAIL return job->continuation(job, context);
+        if constexpr (kFirst) {
+          if (i < job->lcp) {
+            job->continuation = left_side_down_left_spine;
+            MUSTTAIL return job->continuation(job, context);
+          }
         }
         if (n->entryPresent && n->entry.rangeVersion > job->readVersion) {
           job->setResult(false);
@@ -3458,7 +3459,6 @@ PRESERVE_NONE void left_side_iter(CheckJob *job, CheckContext *context) {
       job->remaining =
           job->remaining.subspan(commonLen, job->remaining.size() - commonLen);
     } else if (n->partialKeyLen > int(job->remaining.size())) {
-      assert(job->searchPathLen >= job->prefixLen);
       if (n->entryPresent && n->entry.rangeVersion > job->readVersion) {
         job->setResult(false);
         MUSTTAIL return complete(job, context);
@@ -3475,7 +3475,6 @@ PRESERVE_NONE void left_side_iter(CheckJob *job, CheckContext *context) {
   ++context->tls->range_read_iterations_accum;
 
   if (job->remaining.size() == 0) {
-    assert(job->searchPathLen >= job->prefixLen);
     if (maxVersion(n) > job->readVersion) {
       job->setResult(false);
       MUSTTAIL return complete(job, context);
@@ -3485,12 +3484,10 @@ PRESERVE_NONE void left_side_iter(CheckJob *job, CheckContext *context) {
     }
   }
 
-  if (job->searchPathLen >= job->prefixLen) {
-    if (!checkMaxBetweenExclusive(n, job->remaining[0], 256, job->readVersion,
-                                  context->tls)) {
-      job->setResult(false);
-      MUSTTAIL return complete(job, context);
-    }
+  if (!checkMaxBetweenExclusive(n, job->remaining[0], 256, job->readVersion,
+                                context->tls)) {
+    job->setResult(false);
+    MUSTTAIL return complete(job, context);
   }
 
   auto c = getChild(n, job->remaining[0]);
@@ -3498,12 +3495,6 @@ PRESERVE_NONE void left_side_iter(CheckJob *job, CheckContext *context) {
   if (child == nullptr) {
     auto c = getChildGeq(n, job->remaining[0]);
     if (c != nullptr) {
-      if (job->searchPathLen < job->prefixLen) {
-        job->n = c;
-        job->continuation = left_side_down_left_spine;
-        __builtin_prefetch(job->n);
-        MUSTTAIL return keepGoing(job, context);
-      }
       job->n = c;
       if (maxVersion(job->n) > job->readVersion) {
         job->setResult(false);
@@ -3524,7 +3515,7 @@ PRESERVE_NONE void left_side_iter(CheckJob *job, CheckContext *context) {
   }
 
   job->n = child;
-  job->continuation = leftSideIterTable[c.getType()];
+  job->continuation = leftSideIterTable[false][c.getType()];
   __builtin_prefetch(job->n);
   MUSTTAIL return keepGoing(job, context);
 }