Revert "VM: New calling convention for generated code."

runtime/vm/weak_code.cc

Index: runtime/vm/weak_code.cc
diff --git a/runtime/vm/weak_code.cc b/runtime/vm/weak_code.cc
index 85e623afb9c1b7d138e40c017bb8244be728275f..3177ba63f90ebb6cd97653a801646fc9ff919cbb 100644
--- a/runtime/vm/weak_code.cc
+++ b/runtime/vm/weak_code.cc
@@ -117,15 +117,15 @@ void WeakCodeReferences::DisableCode() {
       // Invalidate the old code object so existing references to it
       // (from optimized code) will fail when invoked.
       if (!CodePatcher::IsEntryPatched(code)) {
-        CodePatcher::PatchEntry(
-            code, Code::Handle(StubCode::FixCallersTarget_entry()->code()));
+        CodePatcher::PatchEntry(code);
       }
     } else {
       // Make non-OSR code non-entrant.
-      if (!CodePatcher::IsEntryPatched(code)) {
-        ReportSwitchingCode(code);
-        CodePatcher::PatchEntry(
-            code, Code::Handle(StubCode::FixCallersTarget_entry()->code()));
+      if (code.GetEntryPatchPc() != 0) {
+        if (!CodePatcher::IsEntryPatched(code)) {
+          ReportSwitchingCode(code);
+          CodePatcher::PatchEntry(code);
+        }
       }
     }
   }