Let NaN flow as double into HBranch

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 1dd27ac9bd7c7cdde01f51f4ac63778fcd9c187e..3e64c1218e0e8e4e57185804b65b37fd398b69fb 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1919,6 +1919,15 @@ void LCodeGen::DoBranch(LBranch* instr) {
       ASSERT(!info()->IsStub());
       __ SmiCompare(reg, Smi::FromInt(0));
       EmitBranch(true_block, false_block, not_equal);
+    } else if (type.IsJSArray()) {
+      EmitBranch(true_block, false_block, no_condition);
+    } else if (type.IsHeapNumber()) {
+      __ xorps(xmm0, xmm0);
+      __ ucomisd(xmm0, FieldOperand(reg, HeapNumber::kValueOffset));
+      EmitBranch(true_block, false_block, not_equal);
+    } else if (type.IsString()) {
+      __ cmpq(FieldOperand(reg, String::kLengthOffset), Immediate(0));
+      EmitBranch(true_block, false_block, not_equal);
     } else {
       Label* true_label = chunk_->GetAssemblyLabel(true_block);
       Label* false_label = chunk_->GetAssemblyLabel(false_block);
@@ -1998,8 +2007,10 @@ void LCodeGen::DoBranch(LBranch* instr) {
         __ bind(&not_heap_number);
       }
 
-      // We've seen something for the first time -> deopt.
-      DeoptimizeIf(no_condition, instr->environment());
+      if (expected != ToBooleanStub::all_types()) {
+        // We've seen something for the first time -> deopt.
+        DeoptimizeIf(no_condition, instr->environment());
+      }
     }
   }
 }