Restore the overflow check to llvm_uadd_with_overflow_i64 to account for the case 0xFFFFFFFFFFFFFFFF + 0x0000000100000001 == 0x0000000100000000.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/library.js b/src/library.js
index 5b58b47f..db84430e 100644
--- a/src/library.js
+++ b/src/library.js
@@ -7560,8 +7560,10 @@ LibraryManager.library = {
     a = a|0; b = b|0; c = c|0; d = d|0;
     var l = 0, h = 0, overflow = 0;
     l = (a + c)>>>0;
-    h = (((b + d)>>>0) + (((l>>>0) < (a>>>0))>>>0))>>>0; // Add carry from low word to high word on overflow.
-    overflow = (((h>>>0) < (b>>>0))>>>0); // Return whether addition overflowed even the high word.
+    h = (b + d)>>>0;
+    overflow = ((h>>>0) < (b>>>0))>>>0; // Return whether addition overflowed even the high word.
+    h = h + (((l>>>0) < (a>>>0))>>>0)>>>0; // Add carry from low word to high word on overflow.
+    overflow = (overflow | ((h == 0)>>>0))>>>0; // Check again for overflow.
     {{{ makeStructuralReturn(['l|0', 'h', 'overflow'], true) }}};
   },