Adding LLVM intrinsic llvm_uadd_with_overflow_i16.

With -O1, sometimes LLVM generates code which calls its intrinsic
llvm_uadd_with_overflow_i16, which was previously missing in
emscripten's library.

This commit adds that intrinsic, and also adds a test which
causes LLVM to call that intrinsic (only in 'o1'). This test
previously failed in 'o1' but now passes.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/library.js b/src/library.js
index 8d68251f..1cb4dd2a 100644
--- a/src/library.js
+++ b/src/library.js
@@ -4759,6 +4759,15 @@ LibraryManager.library = {
   // type_info for void*.
   _ZTIPv: [0],
 
+  llvm_uadd_with_overflow_i16: function(x, y) {
+    x = (x>>>0) & 0xffff;
+    y = (y>>>0) & 0xffff;
+    return {
+      f0: (x+y) & 0xffff,
+      f1: x+y > 65535
+    };
+  },
+
   llvm_uadd_with_overflow_i32: function(x, y) {
     x = x>>>0;
     y = y>>>0;