[wasm] Support validation of asm.js modules with != 3 args.

src/builtins/arm/builtins-arm.cc

Index: src/builtins/arm/builtins-arm.cc
diff --git a/src/builtins/arm/builtins-arm.cc b/src/builtins/arm/builtins-arm.cc
index 63f3fa97a6f0d8dcdec4ba30fa9721d5f9966dcb..0ee3010ed9650a69589c042aed78247c72b298c9 100644
--- a/src/builtins/arm/builtins-arm.cc
+++ b/src/builtins/arm/builtins-arm.cc
@@ -1449,6 +1449,8 @@ void Builtins::Generate_InstantiateAsmJs(MacroAssembler* masm) {
   Label failed;
   {
     FrameScope scope(masm, StackFrame::INTERNAL);
+    // Preserve argument count for later compare.
+    __ Move(r4, r0);
     // Push the number of arguments to the callee.
     __ SmiTag(r0);
     __ push(r0);
@@ -1459,17 +1461,40 @@ void Builtins::Generate_InstantiateAsmJs(MacroAssembler* masm) {
     // The function.
     __ push(r1);
     // Copy arguments from caller (stdlib, foreign, heap).
-    for (int i = 2; i >= 0; --i) {
-      __ ldr(r4, MemOperand(fp, StandardFrameConstants::kCallerSPOffset +
-                                    i * kPointerSize));
-      __ push(r4);
+    Label args_done;
+    for (int j = 0; j < 4; ++j) {
+      Label over;
+      if (j < 3) {
+        __ cmp(r4, Operand(j));
+        __ b(ne, &over);
+      }
+      for (int i = j - 1; i >= 0; --i) {
+        __ ldr(r4, MemOperand(fp, StandardFrameConstants::kCallerSPOffset +
+                                      i * kPointerSize));
+        __ push(r4);
+      }
+      for (int i = 0; i < 3 - j; ++i) {
+        __ PushRoot(Heap::kUndefinedValueRootIndex);
+      }
+      if (j < 3) {
+        __ jmp(&args_done);
+        __ bind(&over);
+      }
     }
+    __ bind(&args_done);
+
     // Call runtime, on success unwind frame, and parent frame.
     __ CallRuntime(Runtime::kInstantiateAsmJs, 4);
     // A smi 0 is returned on failure, an object on success.
     __ JumpIfSmi(r0, &failed);
+
+    __ Drop(2);
+    __ pop(r4);
+    __ SmiUntag(r4);
     scope.GenerateLeaveFrame();
-    __ Drop(4);
+
+    __ add(r4, r4, Operand(1));
+    __ Drop(r4);
     __ Ret();
 
     __ bind(&failed);