Fix approximation of CanDeoptimize() and other small store elimination fixes.

src/lithium-codegen.cc

Index: src/lithium-codegen.cc
diff --git a/src/lithium-codegen.cc b/src/lithium-codegen.cc
index 93ae3101a7779e50b21fe4e542334974bc75758e..1ee23947426d0ce60c69ca26f35098ae206d8b5f 100644
--- a/src/lithium-codegen.cc
+++ b/src/lithium-codegen.cc
@@ -124,18 +124,22 @@ bool LCodeGenBase::GenerateBody() {
 
 void LCodeGenBase::CheckEnvironmentUsage() {
 #ifdef DEBUG
-  bool live_block = true;
+  bool dead_block = false;
   for (int i = 0; i < instructions_->length(); i++) {
     LInstruction* instr = instructions_->at(i);
-    if (instr->IsLabel()) live_block = !LLabel::cast(instr)->HasReplacement();
-    if (live_block &&
-        instr->hydrogen_value()->block()->IsReachable() &&
-        instr->HasEnvironment() &&
-        !instr->environment()->has_been_used()) {
-      FunctionLiteral* lit = info_->function();
-      V8_Fatal(__FILE__, __LINE__, "unused environment in %s <@%d,#%d> %s\n",
-               lit == NULL ? "<UNKNOWN>" : lit->name()->ToCString().get(),
-               i, instr->hydrogen_value()->id(), instr->Mnemonic());
+    HValue* hval = instr->hydrogen_value();
+    if (instr->IsLabel()) dead_block = LLabel::cast(instr)->HasReplacement();
+    if (dead_block || !hval->block()->IsReachable()) continue;
+
+    HInstruction* hinstr = HInstruction::cast(hval);
+    if (!hinstr->CanDeoptimize() && instr->HasEnvironment()) {
+      V8_Fatal(__FILE__, __LINE__, "CanDeoptimize is wrong for %s (%s)\n",
+               hinstr->Mnemonic(), instr->Mnemonic());
+    }
+
+    if (instr->HasEnvironment() && !instr->environment()->has_been_used()) {
+      V8_Fatal(__FILE__, __LINE__, "unused environment for %s (%s)\n",
+               hinstr->Mnemonic(), instr->Mnemonic());
     }
   }
 #endif