[strong] Function arity check should be based on required parameters

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 8d2a67af8cd0dfc0123abbb7de321f96b56c3933..088dd32949ba2710446eb6e92d50b10e8facedc4 100644
--- a/src/arm64/builtins-arm64.cc
+++ b/src/arm64/builtins-arm64.cc
@@ -1740,14 +1740,21 @@ void Builtins::Generate_ArgumentsAdaptorTrampoline(MacroAssembler* masm) {
     Register scratch1 = x13, scratch2 = x14;
 
     // If the function is strong we need to throw an error.
-    Label weak_function;
+    Label no_strong_error;
     __ Ldr(scratch1,
            FieldMemOperand(function, JSFunction::kSharedFunctionInfoOffset));
     __ Ldr(scratch2.W(),
            FieldMemOperand(scratch1, SharedFunctionInfo::kCompilerHintsOffset));
     __ TestAndBranchIfAllClear(scratch2.W(),
                                (1 << SharedFunctionInfo::kStrongModeFunction),
-                               &weak_function);
+                               &no_strong_error);
+
+    // What we really care about is the required number of arguments.
+    __ Ldrsh(scratch2,

[Rodolph Perfetta, 2015/05/19 14:37:05]

This will load a 16bit value which is not what you meant. Load into a W register
(32-bit) should accomplish what you intended:

  __ Ldr(scratch2.W(), FieldMem...);

+             FieldMemOperand(scratch1, SharedFunctionInfo::kLengthOffset));
+    __ lsr(scratch2, scratch2, 1);
+    __ Cmp(argc_actual, scratch2);

[Rodolph Perfetta, 2015/05/19 14:37:06]

the two instructions above can be merged:

  __ Cmp(argc_actual, Operand(scratch2, LSR, 1));

+    __ B(ge, &no_strong_error);
 
     {
       FrameScope frame(masm, StackFrame::MANUAL);
@@ -1755,7 +1762,7 @@ void Builtins::Generate_ArgumentsAdaptorTrampoline(MacroAssembler* masm) {
       __ CallRuntime(Runtime::kThrowStrongModeTooFewArguments, 0);
     }
 
-    __ bind(&weak_function);
+    __ bind(&no_strong_error);

[Rodolph Perfetta, 2015/05/19 14:37:06]

No part of your patch but we should use the macro assembler so Bind(...)

[arv (Not doing code reviews), 2015/05/19 14:56:13]

I added that bind so I'm happy to change it to Bind to get the assertion.

     EnterArgumentsAdaptorFrame(masm);
 
     __ Lsl(argc_expected, argc_expected, kPointerSizeLog2);