Hooking up asm-wasm conversion.

src/x87/builtins-x87.cc

Index: src/x87/builtins-x87.cc
diff --git a/src/x87/builtins-x87.cc b/src/x87/builtins-x87.cc
index 0600f0d3ccc809953a6019de7fe4d2fc7443ca6e..3631002969e50c8f7c6f44b8285800a1c6a554c8 100644
--- a/src/x87/builtins-x87.cc
+++ b/src/x87/builtins-x87.cc
@@ -1018,6 +1018,46 @@ void Builtins::Generate_CompileOptimizedConcurrent(MacroAssembler* masm) {
   GenerateTailCallToReturnedCode(masm, Runtime::kCompileOptimized_Concurrent);
 }
 
+void Builtins::Generate_InstantiateAsmJs(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- eax : argument count (preserved for callee)
+  //  -- edx : new target (preserved for callee)
+  //  -- edi : target function (preserved for callee)
+  // -----------------------------------
+  Label failed;
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    // Push the number of arguments to the callee.
+    __ SmiTag(eax);
+    __ push(eax);
+    // Push a copy of the target function and the new target.
+    __ push(edi);
+    __ push(edx);
+
+    // The function.
+    __ push(edi);
+    // Copy arguments from caller (stdlib, foreign, heap).
+    for (int i = 2; i >= 0; --i) {
+      __ push(Operand(
+          ebp, StandardFrameConstants::kCallerSPOffset + i * kPointerSize));
+    }
+    // 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(eax, &failed, Label::kNear);
+    scope.GenerateLeaveFrame();
+    __ ret(4 * kPointerSize);
+
+    __ bind(&failed);
+    // Restore target function and new target.
+    __ pop(edx);
+    __ pop(edi);
+    __ pop(eax);
+    __ SmiUntag(eax);
+  }
+  // On failure, tail call back to regular js.
+  GenerateTailCallToReturnedCode(masm, Runtime::kCompileLazy);
+}
 
 static void GenerateMakeCodeYoungAgainCommon(MacroAssembler* masm) {
   // For now, we are relying on the fact that make_code_young doesn't do any