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

src/builtins/s390/builtins-s390.cc

Index: src/builtins/s390/builtins-s390.cc
diff --git a/src/builtins/s390/builtins-s390.cc b/src/builtins/s390/builtins-s390.cc
index aaa31bde27f463757561f2537faca5341df34837..4e7b585e32052142e50b48037504111e689c818e 100644
--- a/src/builtins/s390/builtins-s390.cc
+++ b/src/builtins/s390/builtins-s390.cc
@@ -1465,23 +1465,48 @@ void Builtins::Generate_InstantiateAsmJs(MacroAssembler* masm) {
   Label failed;
   {
     FrameScope scope(masm, StackFrame::INTERNAL);
+    // Preserve argument count for later compare.
+    __ Move(r4, r2);
     // Push a copy of the target function and the new target.
     __ SmiTag(r2);
     // Push another copy as a parameter to the runtime call.
     __ Push(r2, r3, r5, r3);
 
     // Copy arguments from caller (stdlib, foreign, heap).
-    for (int i = 2; i >= 0; --i) {
-      __ LoadP(r4, MemOperand(fp, StandardFrameConstants::kCallerSPOffset +
-                                      i * kPointerSize));
-      __ push(r4);
+    Label args_done;
+    for (int j = 0; j < 4; ++j) {
+      Label over;
+      if (j < 3) {
+        __ CmpP(r4, Operand(j));
+        __ b(ne, &over);
+      }
+      for (int i = j - 1; i >= 0; --i) {
+        __ LoadP(r9, MemOperand(fp, StandardFrameConstants::kCallerSPOffset +
+                                        i * kPointerSize));
+        __ push(r9);
+      }
+      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(r2, &failed);
+
+    __ Drop(2);
+    __ pop(r4);
+    __ SmiUntag(r4);
     scope.GenerateLeaveFrame();
-    __ Drop(4);
+
+    __ AddP(r4, r4, Operand(1));
+    __ Drop(r4, r7);
     __ Ret();
 
     __ bind(&failed);