[generators] Fix loading of FormalParameterCount on 64bit archs.

src/arm64/builtins-arm64.cc

Index: src/arm64/builtins-arm64.cc
diff --git a/src/arm64/builtins-arm64.cc b/src/arm64/builtins-arm64.cc
index 67a354e35c57734793e9b1966c704fc18502dcc3..11e1cde61548527839a6ee6e03dd4162157019fe 100644
--- a/src/arm64/builtins-arm64.cc
+++ b/src/arm64/builtins-arm64.cc
@@ -775,9 +775,8 @@ void Builtins::Generate_ResumeGeneratorTrampoline(MacroAssembler* masm) {
   // New-style (ignition/turbofan) generator object
   {
     __ Ldr(x0, FieldMemOperand(x4, JSFunction::kSharedFunctionInfoOffset));
-    __ Ldr(x0,
+    __ Ldr(w0,
          FieldMemOperand(x0, SharedFunctionInfo::kFormalParameterCountOffset));
-    __ SmiUntag(x0);
     // We abuse new.target both to indicate that this is a resume call and to
     // pass in the generator object.  In ordinary calls, new.target is always
     // undefined because generator functions are non-constructable.