From 129e0f05b1d43949d06a34db663552929fa3b89c Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Fri, 2 Feb 2024 15:51:49 -0800
Subject: [PATCH] Fix glDrawElements under CAN_ADDRESS_2GB

This is partially a workround for #21250
---
 .circleci/config.yml |  1 +
 src/library_glemu.js | 14 ++++++++++----
 src/parseTools.js    |  1 +
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index b13bb169e4744..586e0f56386b1 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -821,6 +821,7 @@ jobs:
             browser_2gb.test_cubegeom
             browser_2gb.test_cubegeom_normal
             browser_2gb.test_cubegeom_normal_dap
+            browser_2gb.test_cubegeom_normal_dap_far
             "
   test-browser-chrome-wasm64-4gb:
     executor: bionic
diff --git a/src/library_glemu.js b/src/library_glemu.js
index ddca86d6bce1b..9ebc0c9524773 100644
--- a/src/library_glemu.js
+++ b/src/library_glemu.js
@@ -2940,9 +2940,9 @@ var LibraryGLEmulation = {
       // Detect which case we are in by using a quick heuristic by examining the
       // strides of the buffers. If all the buffers have identical stride, we
       // assume we have case (2), otherwise we have something more complex.
-      var clientStartPointer = 0x7FFFFFFF;
+      var clientStartPointer = {{{ POINTER_MAX }}};
       var bytes = 0; // Total number of bytes taken up by a single vertex.
-      var minStride = 0x7FFFFFFF;
+      var minStride = {{{ POINTER_MAX }}};
       var maxStride = 0;
       var attributes = GLImmediate.liveClientAttributes;
       attributes.length = 0;
@@ -3544,8 +3544,14 @@ var LibraryGLEmulation = {
       GLImmediate.firstVertex = end ? start : HEAP8.length; // if we don't know the start, set an invalid value and we will calculate it later from the indices
       GLImmediate.lastVertex = end ? end + 1 : 0;
       start = GLImmediate.vertexPointer;
-      end = end ? GLImmediate.vertexPointer + (end+1)*GLImmediate.stride : undefined;
-      GLImmediate.vertexData = HEAPF32.subarray({{{ getHeapOffset('start', 'float') }}}, end ? {{{ getHeapOffset('end', 'float') }}} : undefined);
+      // TODO(sbc): Combine these two subarray calls back into a single one if
+      // we ever fix https://github.com/emscripten-core/emscripten/issues/21250.
+      if (end) {
+        end = GLImmediate.vertexPointer + (end +1 ) * GLImmediate.stride;
+        GLImmediate.vertexData = HEAPF32.subarray({{{ getHeapOffset('start', 'float') }}}, {{{ getHeapOffset('end', 'float') }}});
+      } else {
+        GLImmediate.vertexData = HEAPF32.subarray({{{ getHeapOffset('start', 'float') }}});
+      }
     }
     GLImmediate.flush(count, 0, indices);
     GLImmediate.mode = -1;
diff --git a/src/parseTools.js b/src/parseTools.js
index ef91fc93198bb..c56e6d9f5dd7b 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -176,6 +176,7 @@ function needsQuoting(ident) {
 }
 
 globalThis.POINTER_SIZE = MEMORY64 ? 8 : 4;
+globalThis.POINTER_MAX = MEMORY64 ? 'Number.MAX_SAFE_INTEGER' : '2**32';
 globalThis.STACK_ALIGN = 16;
 const POINTER_BITS = POINTER_SIZE * 8;
 const POINTER_TYPE = `u${POINTER_BITS}`;