From 47cae7de294532e6584a275acadda95d9cbb0a5a Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Tue, 7 Apr 2026 11:23:33 -0700
Subject: [PATCH] Remove `performance.now` hackery which only exists for node
 v18 + `DETERMINISTIC`. NFC

I don't think its worth the extra complexity to support `DETERMINISTIC` on
node v18 since that combination is likely extremely rare.

(I don't know of any active users of `-sDETERMINISTIC` myself).
---
 src/deterministic.js |  1 -
 src/lib/libcore.js   | 12 ++++++------
 src/parseTools.mjs   | 12 ------------
 test/test_other.py   |  2 ++
 tools/link.py        |  3 +++
 5 files changed, 11 insertions(+), 19 deletions(-)

diff --git a/src/deterministic.js b/src/deterministic.js
index 9c4b3ca5bd74f..4eef50459d111 100644
--- a/src/deterministic.js
+++ b/src/deterministic.js
@@ -20,7 +20,6 @@ Date.now = deterministicNow;
 // Note: this approach does not work on certain versions of Node.js
 // Specifically it seems like its not possible to override performance.now on
 // node v16 through v18.
-// See getPerformanceNow in parseTools.mjs for how we deal with this.
 if (globalThis.performance) performance.now = deterministicNow;
 
 // for consistency between different builds than between runs of the same build
diff --git a/src/lib/libcore.js b/src/lib/libcore.js
index ee9cfcedef751..3857db9bd84fb 100644
--- a/src/lib/libcore.js
+++ b/src/lib/libcore.js
@@ -1355,13 +1355,13 @@ addToLibrary({
 
   emscripten_date_now: () => Date.now(),
 
-  emscripten_performance_now: () => {{{ getPerformanceNow() }}}(),
+  emscripten_performance_now: () => performance.now(),
 
 #if PTHREADS && !AUDIO_WORKLET
   // Pthreads need their clocks synchronized to the execution of the main
   // thread, so, when using them, make sure to adjust all timings to the
   // respective time origins.
-  emscripten_get_now: () => performance.timeOrigin + {{{ getPerformanceNow() }}}(),
+  emscripten_get_now: () => performance.timeOrigin + performance.now(),
 #else
 #if AUDIO_WORKLET // https://github.com/WebAudio/web-audio-api/issues/2413
   emscripten_get_now: `;
@@ -1369,11 +1369,11 @@ addToLibrary({
     // (https://github.com/WebAudio/web-audio-api/issues/2527), so if building
     // with
     // Audio Worklets enabled, do a dynamic check for its presence.
-    if (globalThis.performance && {{{ getPerformanceNow() }}}) {
+    if (globalThis.performance && performance.now) {
 #if PTHREADS
-      _emscripten_get_now = () => performance.timeOrigin + {{{ getPerformanceNow() }}}();
+      _emscripten_get_now = () => performance.timeOrigin + performance.now();
 #else
-      _emscripten_get_now = () => {{{ getPerformanceNow() }}}();
+      _emscripten_get_now = () => performance.now();
 #endif
     } else {
       _emscripten_get_now = Date.now;
@@ -1383,7 +1383,7 @@ addToLibrary({
   // Modern environment where performance.now() is supported:
   // N.B. a shorter form "_emscripten_get_now = performance.now;" is
   // unfortunately not allowed even in current browsers (e.g. FF Nightly 75).
-  emscripten_get_now: () => {{{ getPerformanceNow() }}}(),
+  emscripten_get_now: () => performance.now(),
 #endif
 #endif
 
diff --git a/src/parseTools.mjs b/src/parseTools.mjs
index 544d7bd808250..2b79bf12a31bf 100644
--- a/src/parseTools.mjs
+++ b/src/parseTools.mjs
@@ -1105,17 +1105,6 @@ function formattedMinNodeVersion() {
   return `v${major}.${minor}.${rev}`;
 }
 
-function getPerformanceNow() {
-  // This is needed to support Node.js v16 - v18 where `performance.now`
-  // cannot be overridden in the normal way.
-  // TODO(sbc): remove this once we drop support for these versions.
-  if (DETERMINISTIC && ENVIRONMENT_MAY_BE_NODE) {
-    return 'deterministicNow';
-  } else {
-    return 'performance.now';
-  }
-}
-
 function ENVIRONMENT_IS_MAIN_THREAD() {
   return `(!${ENVIRONMENT_IS_WORKER_THREAD()})`;
 }
@@ -1231,7 +1220,6 @@ addToCompileTimeContext({
   getHeapForType,
   getHeapOffset,
   getNativeTypeSize,
-  getPerformanceNow,
   getUnsharedTextDecoderView,
   hasExportedSymbol,
   isSymbolNeeded,
diff --git a/test/test_other.py b/test/test_other.py
index 3ac05d902c1ee..dead08c617df6 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -12059,6 +12059,8 @@ def test_deterministic(self):
   printf("JS random: %d\n", EM_ASM_INT({ return Math.random() }));
 }
 ''')
+    if not self.try_require_node_version(19):
+      self.skipTest('-sDETERMINISTIC requires node v19 or above')
     self.run_process([EMCC, 'src.c', '-sDETERMINISTIC'] + self.get_cflags())
     one = self.run_js('a.out.js')
     # ensure even if the time resolution is 1 second, that if we see the real
diff --git a/tools/link.py b/tools/link.py
index d4cab9999c9f2..10f0a4a48b295 100644
--- a/tools/link.py
+++ b/tools/link.py
@@ -1366,6 +1366,9 @@ def limit_incoming_module_api():
 
   check_browser_versions()
 
+  if settings.DETERMINISTIC and settings.MIN_NODE_VERSION < 190000:
+    exit_with_error('DETERMINISTIC does not work with node < v19')
+
   if settings.POLYFILL:
     # Emscripten requires certain ES6+ constructs by default in library code
     # - (various ES6 operators available in all browsers listed below)