From ffd5abc581e0643733bfda98c6b8b8f6d03ec78d Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Thu, 22 Oct 2026 14:33:38 -0700
Subject: [PATCH 1/2] Calculate transitive JS library deps after
 `symbolHandler` in `--symbols-only` mode. NFC

Previously, `getTransitiveDeps` was called inside `addFromLibrary` while
`symbolHandler` was still iterating through `symbolsNeeded` and mutating
`__deps` (such as adding `setTempRet0` for i64-returning functions
without `WASM_BIGINT`).

Compute `symbolDeps` in the `if (symbolsOnly)` block after
`symbolHandler` completes so that all direct `__deps` are populated
before traversing the dependency graph.

Split out from #27995.
---
 src/jsifier.mjs | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/jsifier.mjs b/src/jsifier.mjs
index 83fa44163cf00..3fdee57fa5f12 100644
--- a/src/jsifier.mjs
+++ b/src/jsifier.mjs
@@ -415,7 +415,6 @@ const PROXY_SYNC_ASYNC = 2;
 export async function runJSify(outputFile, symbolsOnly) {
   const libraryItems = [];
   const libraryAliases = [];
-  const symbolDeps = {};
   const asyncFuncs = [];
   let postSets = [];
 
@@ -629,13 +628,6 @@ function(${args}) {
       }
 
       if (symbolsOnly) {
-        if (LibraryManager.library.hasOwnProperty(symbol)) {
-          // Resolve aliases before looking up deps
-          var transitiveDeps = getTransitiveDeps(symbol);
-          symbolDeps[symbol] = transitiveDeps.filter(
-            (d) => !isJsOnlySymbol(d) && !(d in LibraryManager.library),
-          );
-        }
         return;
       }
 
@@ -1003,6 +995,15 @@ var proxiedFunctionTable = [
   timer.stop('symbolHandler');
 
   if (symbolsOnly) {
+    const symbolDeps = {};
+    for (const sym of Object.keys(LibraryManager.library)) {
+      if (!isDecorator(sym)) {
+        const transitiveDeps = getTransitiveDeps(sym);
+        symbolDeps[sym] = transitiveDeps.filter(
+          (d) => !isJsOnlySymbol(d) && !(d in LibraryManager.library),
+        );
+      }
+    }
     writeOutput(
       JSON.stringify({
         deps: symbolDeps,

From 85466163e7e844d3c7da491886d068a44366279c Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Thu, 22 Oct 2026 15:42:41 -0700
Subject: [PATCH 2/2] Memoize `getTransitiveDeps` in `src/jsifier.mjs`. NFC

Cache the computed transitive dependency list for each symbol in
`transitiveDepsCache` and reuse cached results when traversing
dependencies in subsequent `getTransitiveDeps` calls. Only completed
top-level traversals are inserted into the cache so that cyclic
dependencies (such as `$FS` <-> `$MEMFS`) are handled safely without
caching partial results.

In `tools/compiler.mjs --symbols-only`, this reduces graph node visits
in `getTransitiveDeps` by ~9x (from 39,349 to 4,381), cutting the
`symbolDeps` calculation time by ~41% (from ~16.0ms to ~9.5ms) and
overall `--symbols-only` execution time by ~4.6% (from ~152ms to
~145ms).

See: #28052
---
 src/jsifier.mjs | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/jsifier.mjs b/src/jsifier.mjs
index 3fdee57fa5f12..70f1b1a46cad6 100644
--- a/src/jsifier.mjs
+++ b/src/jsifier.mjs
@@ -127,27 +127,40 @@ function isDefined(symName) {
   return false;
 }
 
+const transitiveDepsCache = new Map();
+
 function getTransitiveDeps(symbol) {
-  // TODO(sbc): Use some kind of cache to avoid quadratic behaviour here.
+  let result = transitiveDepsCache.get(symbol);
+  if (result) {
+    return result;
+  }
   const transitiveDeps = new Set();
   const seen = new Set();
   const toVisit = [symbol];
   while (toVisit.length) {
     const sym = toVisit.pop();
     if (!seen.has(sym)) {
-      let directDeps = LibraryManager.library[sym + '__deps'] ?? [];
-      directDeps = directDeps.filter((d) => typeof d === 'string');
-      for (const dep of directDeps) {
+      const cached = transitiveDepsCache.get(sym);
+      let deps = cached;
+      if (!deps) {
+        deps = LibraryManager.library[sym + '__deps'] ?? [];
+        deps = deps.filter((d) => typeof d === 'string');
+      }
+      for (const dep of deps) {
         if (!transitiveDeps.has(dep)) {
           debugLog(`adding dependency ${symbol} -> ${dep}`);
+          transitiveDeps.add(dep);
+          if (!cached) {
+            toVisit.push(dep);
+          }
         }
-        transitiveDeps.add(dep);
-        toVisit.push(dep);
       }
       seen.add(sym);
     }
   }
-  return Array.from(transitiveDeps);
+  result = Array.from(transitiveDeps);
+  transitiveDepsCache.set(symbol, result);
+  return result;
 }
 
 function shouldPreprocess(fileName) {
@@ -413,6 +426,7 @@ const PROXY_SYNC = 1;
 const PROXY_SYNC_ASYNC = 2;
 
 export async function runJSify(outputFile, symbolsOnly) {
+  transitiveDepsCache.clear();
   const libraryItems = [];
   const libraryAliases = [];
   const asyncFuncs = [];