[hydrogen] don't bailout assignments to consts

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index 71405b6344aedf410dcc52743e2eec2d59f2637a..6cb4e47f19a07a58c886ce04e9b662ee1fc3b8b8 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -2167,7 +2167,17 @@ void LCodeGen::DoLoadContextSlot(LLoadContextSlot* instr) {
 void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
   Register context = ToRegister(instr->context());
   Register value = ToRegister(instr->value());
+  Register scratch = scratch0();
   MemOperand target = ContextOperand(context, instr->slot_index());
+
+  Label skip_assignment;
+
+  if (instr->RequiresHoleCheck()) {
+    __ lw(scratch, target);
+    __ Branch(&skip_assignment, ne, scratch,
+              Operand(factory()->the_hole_value()));
+  }
+
   __ sw(value, target);
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     HType type = instr->hydrogen()->value()->type();
@@ -2182,6 +2192,8 @@ void LCodeGen::DoStoreContextSlot(LStoreContextSlot* instr) {
                               EMIT_REMEMBERED_SET,
                               check_needed);
   }
+
+  __ bind(&skip_assignment);
 }