A64: Fix result in CompileStringCharAtCall and CompileStringCharCodeAtCall.

src/a64/stub-cache-a64.cc

Index: src/a64/stub-cache-a64.cc
diff --git a/src/a64/stub-cache-a64.cc b/src/a64/stub-cache-a64.cc
index 43f292f690ae7cf574b1dc220e8acdb38ffcfac9..b8adb5d100473e31af119a1ee2d7cd742d731974 100644
--- a/src/a64/stub-cache-a64.cc
+++ b/src/a64/stub-cache-a64.cc
@@ -2049,7 +2049,7 @@ Handle<Code> CallStubCompiler::CompileStringCharCodeAtCall(
 
   if (index_out_of_range.is_linked()) {
     __ Bind(&index_out_of_range);
-    __ LoadRoot(result, Heap::kNanValueRootIndex);
+    __ LoadRoot(x0, Heap::kNanValueRootIndex);
     __ Drop(argc + 1);
     __ Ret();
   }
@@ -2118,7 +2118,7 @@ Handle<Code> CallStubCompiler::CompileStringCharAtCall(
 
   if (index_out_of_range.is_linked()) {
     __ Bind(&index_out_of_range);
-    __ LoadRoot(result, Heap::kempty_stringRootIndex);
+    __ LoadRoot(x0, Heap::kempty_stringRootIndex);
     __ Drop(argc + 1);
     __ Ret();
   }