Use register allocator for context on x64.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 042a47080895f340c98feabba695b346f1f548a5..c71ed62a3eca00832a799f0c8da9315d39e7ac32 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -4384,6 +4384,7 @@ void LCodeGen::DoCallNewArray(LCallNewArray* instr) {
 
 
 void LCodeGen::DoCallRuntime(LCallRuntime* instr) {
+  ASSERT(ToRegister(instr->context()).is(esi));
   CallRuntime(instr->function(), instr->arity(), instr, instr->save_doubles());
 }
 
@@ -4957,6 +4958,7 @@ void LCodeGen::DoDeferredStringCharFromCode(LStringCharFromCode* instr) {
 
 
 void LCodeGen::DoStringAdd(LStringAdd* instr) {
+  ASSERT(ToRegister(instr->context()).is(esi));
   EmitPushTaggedOperand(instr->left());
   EmitPushTaggedOperand(instr->right());
   StringAddStub stub(instr->hydrogen()->flags());
@@ -6050,6 +6052,7 @@ void LCodeGen::DoFunctionLiteral(LFunctionLiteral* instr) {
 
 
 void LCodeGen::DoTypeof(LTypeof* instr) {
+  ASSERT(ToRegister(instr->context()).is(esi));
   LOperand* input = instr->value();
   EmitPushTaggedOperand(input);
   CallRuntime(Runtime::kTypeof, 1, instr);
@@ -6294,6 +6297,7 @@ void LCodeGen::DoOsrEntry(LOsrEntry* instr) {
 
 
 void LCodeGen::DoForInPrepareMap(LForInPrepareMap* instr) {
+  ASSERT(ToRegister(instr->context()).is(esi));
   __ cmp(eax, isolate()->factory()->undefined_value());
   DeoptimizeIf(equal, instr->environment());