Let NaN flow as double into HBranch

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 885b2e304e3a57b8cb473a02ed61a069379ac017..e5324fc606a353c93c24e475c788403368b163bd 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1060,6 +1060,8 @@ LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
     return new(zone()) LGoto(successor->block_id());
   }
 
+  ToBooleanStub::Types expected = instr->expected_input_types();
+
   // Untagged integers or doubles, smis and booleans don't require a
   // deoptimization environment nor a temp register.
   Representation rep = value->representation();
@@ -1068,12 +1070,17 @@ LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
     return new(zone()) LBranch(UseRegister(value), NULL);
   }
 
-  ToBooleanStub::Types expected = instr->expected_input_types();
+  bool needs_temp = expected.NeedsMap() || expected.IsEmpty();
+  LOperand* temp = needs_temp ? TempRegister() : NULL;
+
+  // The Generic stub does not have a deopt, so we need no environment.
+  if (expected.IsGeneric()) {
+    return new(zone()) LBranch(UseRegister(value), temp);
+  }
+
   // We need a temporary register when we have to access the map *or* we have
   // no type info yet, in which case we handle all cases (including the ones
   // involving maps).
-  bool needs_temp = expected.NeedsMap() || expected.IsEmpty();
-  LOperand* temp = needs_temp ? TempRegister() : NULL;
   return AssignEnvironment(new(zone()) LBranch(UseRegister(value), temp));
 }