X64: Make the ToBoolean inline code do even less if the value is known to be a smi.

src/x64/codegen-x64.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5324 matching lines @@
   Result value = frame_->Pop();
   value.ToRegister();
 
   if (value.is_number()) {
     // Fast case if TypeInfo indicates only numbers.
     if (FLAG_debug_code) {
       __ AbortIfNotNumber(value.reg());
     }
     // Smi => false iff zero.
     __ SmiCompare(value.reg(), Smi::FromInt(0));
-    dest->false_target()->Branch(equal);
-    Condition is_smi = masm_->CheckSmi(value.reg());
-    dest->true_target()->Branch(is_smi);
-    __ xorpd(xmm0, xmm0);
-    __ ucomisd(xmm0, FieldOperand(value.reg(), HeapNumber::kValueOffset));
-    value.Unuse();
-    dest->Split(not_zero);
+    if (value.is_smi()) {
+      value.Unuse();
+      dest->Split(not_zero);
+    } else {
+      dest->false_target()->Branch(equal);

[William Hesse, 2010/06/29 10:50:10]

Why not also have a case for if value.is_double()?

[Lasse Reichstein, 2010/06/29 14:13:30]

I doubt it will happen in practice that we convert a value to boolean that we
*know* is a double.

I don't know whether we would want to do something for the known string case.
Again, I don't expect known string operation results to be used as booleans
much.

Maybe we should add a counter for the other special cases and see if they are
hit.

+      Condition is_smi = masm_->CheckSmi(value.reg());
+      dest->true_target()->Branch(is_smi);
+      __ xorpd(xmm0, xmm0);
+      __ ucomisd(xmm0, FieldOperand(value.reg(), HeapNumber::kValueOffset));
+      value.Unuse();
+      dest->Split(not_zero);
+    }
   } else {
     // Fast case checks.
     // 'false' => false.
     __ CompareRoot(value.reg(), Heap::kFalseValueRootIndex);
     dest->false_target()->Branch(equal);
 
     // 'true' => true.
     __ CompareRoot(value.reg(), Heap::kTrueValueRootIndex);
     dest->true_target()->Branch(equal);
 
@@ skipping 6539 matching lines @@
 }
 
 #endif
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64