Fix an assertion failure in the full code generator.

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 724a7c598ac6fbfb520cb81f8397b9e0fd729fcf..b6e81b0f14a47b2ccd515bc889cb026c3db317bb 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -2006,16 +2006,21 @@ void FullCodeGenerator::VisitCall(Call* expr) {
       // Call to a keyed property.
       // For a synthetic property use keyed load IC followed by function call,
       // for a regular property use keyed EmitCallIC.
-      { PreservePositionScope scope(masm()->positions_recorder());
-        VisitForStackValue(prop->obj());
-      }
       if (prop->is_synthetic()) {
-        { PreservePositionScope scope(masm()->positions_recorder());
-          VisitForAccumulatorValue(prop->key());
-        }
+        // Do not visit the object and key subexpressions (they are shared
+        // by all occurrences of the same rewritten parameter).
+        ASSERT(prop->obj()->AsVariableProxy() != NULL);
+        ASSERT(prop->obj()->AsVariableProxy()->var()->AsSlot() != NULL);
+        Slot* slot = prop->obj()->AsVariableProxy()->var()->AsSlot();
+        MemOperand operand = EmitSlotSearch(slot, rdx);
+        __ movq(rdx, operand);
+
+        ASSERT(prop->key()->AsLiteral() != NULL);
+        ASSERT(prop->key()->AsLiteral()->handle()->IsSmi());
+        __ Move(rax, prop->key()->AsLiteral()->handle());
+
         // Record source code position for IC call.
         SetSourcePosition(prop->position());
-        __ pop(rdx);  // We do not need to keep the receiver.
 
         Handle<Code> ic(Builtins::builtin(Builtins::KeyedLoadIC_Initialize));
         EmitCallIC(ic, RelocInfo::CODE_TARGET);
@@ -2026,6 +2031,9 @@ void FullCodeGenerator::VisitCall(Call* expr) {
         __ push(FieldOperand(rcx, GlobalObject::kGlobalReceiverOffset));
         EmitCallWithStub(expr);
       } else {
+        { PreservePositionScope scope(masm()->positions_recorder());
+          VisitForStackValue(prop->obj());
+        }
         EmitKeyedCallWithIC(expr, prop->key(), RelocInfo::CODE_TARGET);
       }
     }