Implement a type recording ToBoolean IC.

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
===================================================================
--- src/ia32/code-stubs-ia32.cc	(revision 8701)
+++ src/ia32/code-stubs-ia32.cc	(working copy)
@@ -236,72 +236,163 @@
 }
 
 
-// The stub returns zero for false, and a non-zero value for true.
+// The stub expects its argument on the stack and returns its result in tos_:
+// zero for false, and a non-zero value for true.
 void ToBooleanStub::Generate(MacroAssembler* masm) {
-  Label false_result, true_result, not_string;
+  Label patch;
   Factory* factory = masm->isolate()->factory();
   const Register map = edx;
 
-  __ mov(eax, Operand(esp, 1 * kPointerSize));
+  if (!types_.IsEmpty()) {
+    __ mov(eax, Operand(esp, 1 * kPointerSize));
+  }
 
   // undefined -> false
-  __ cmp(eax, factory->undefined_value());
-  __ j(equal, &false_result);
+  CheckOddball(masm, UNDEFINED, factory->undefined_value(), false, &patch);
 
   // Boolean -> its value
-  __ cmp(eax, factory->false_value());
-  __ j(equal, &false_result);
-  __ cmp(eax, factory->true_value());
-  __ j(equal, &true_result);
+  CheckOddball(masm, BOOLEAN, factory->false_value(), false, &patch);
+  CheckOddball(masm, BOOLEAN, factory->true_value(), true, &patch);
 
-  // Smis: 0 -> false, all other -> true
-  __ test(eax, Operand(eax));
-  __ j(zero, &false_result);
-  __ JumpIfSmi(eax, &true_result);
-
   // 'null' -> false.
-  __ cmp(eax, factory->null_value());
-  __ j(equal, &false_result, Label::kNear);
+  CheckOddball(masm, NULL_TYPE, factory->null_value(), false, &patch);
 
-  // Get the map of the heap object.
-  __ mov(map, FieldOperand(eax, HeapObject::kMapOffset));
+  bool need_map =
+      types_.Contains(UNDETECTABLE) |
+      types_.Contains(SPEC_OBJECT) |
+      types_.Contains(STRING) |
+      types_.Contains(HEAP_NUMBER) |
+      types_.Contains(INTERNAL_OBJECT);
 
-  // Undetectable -> false.
-  __ test_b(FieldOperand(map, Map::kBitFieldOffset),
-            1 << Map::kIsUndetectable);
-  __ j(not_zero, &false_result, Label::kNear);
+  if (types_.Contains(SMI)) {
+    // Smis: 0 -> false, all other -> true
+    Label not_smi;
+    __ JumpIfNotSmi(eax, &not_smi, Label::kNear);
+    __ ret(1 * kPointerSize);  // eax contains the correct value already
+    __ bind(&not_smi);
+  } else if (need_map) {
+    // If we need a map later and have a Smi -> patch.
+    __ JumpIfSmi(eax, &patch, Label::kNear);
+  }
 
-  // JavaScript object -> true.
-  __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
-  __ j(above_equal, &true_result, Label::kNear);
+  if (need_map) {
+    __ mov(map, FieldOperand(eax, HeapObject::kMapOffset));
 
-  // String value -> false iff empty.
-  __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
-  __ j(above_equal, &not_string, Label::kNear);
-  __ cmp(FieldOperand(eax, String::kLengthOffset), Immediate(0));
-  __ j(zero, &false_result, Label::kNear);
-  __ jmp(&true_result, Label::kNear);
+    // Everything with a map could be undetectable, so check this now.
+    __ test_b(FieldOperand(map, Map::kBitFieldOffset),
+              1 << Map::kIsUndetectable);
+    if (types_.Contains(UNDETECTABLE)) {
+      // Undetectable -> false.
+      Label not_undetectable;
+      __ j(zero, &not_undetectable, Label::kNear);
+      __ xor_(tos_, Operand(tos_));

[Vitaly Repeshko, 2011/07/21 13:17:23]

The macro assembler has Set macro that emits the optimal instruction without
hurting readability.

[Sven Panne, 2011/07/21 13:49:28]

I didn't know that one, thanks. :-)

+      __ ret(1 * kPointerSize);
+      __ bind(&not_undetectable);
+    } else {
+      // We've seen an undetectable value for the first time -> patch.
+      __ j(not_zero, &patch, Label::kNear);
+    }
+  }
 
-  __ bind(&not_string);
-  // HeapNumber -> false iff +0, -0, or NaN.
-  __ cmp(map, factory->heap_number_map());
-  __ j(not_equal, &true_result, Label::kNear);
-  __ fldz();
-  __ fld_d(FieldOperand(eax, HeapNumber::kValueOffset));
-  __ FCmp();
-  __ j(zero, &false_result, Label::kNear);
-  // Fall through to |true_result|.
+  if (types_.Contains(SPEC_OBJECT)) {
+    // spec object -> true.
+    Label not_js_object;
+    __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
+    __ j(below, &not_js_object, Label::kNear);
+    __ mov(tos_, 1);
+    __ ret(1 * kPointerSize);
+    __ bind(&not_js_object);
+  } else if (types_.Contains(INTERNAL_OBJECT)) {
+    // We've seen a spec object for the first time -> patch.
+    __ CmpInstanceType(map, FIRST_SPEC_OBJECT_TYPE);
+    __ j(above_equal, &patch, Label::kNear);
+  }
 
-  // Return 1/0 for true/false in tos_.
-  __ bind(&true_result);
-  __ mov(tos_, 1);
-  __ ret(1 * kPointerSize);
-  __ bind(&false_result);
-  __ mov(tos_, 0);
-  __ ret(1 * kPointerSize);
+  if (types_.Contains(STRING)) {
+    // String value -> false iff empty.
+    Label not_string;
+    __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
+    __ j(above_equal, &not_string, Label::kNear);
+    __ mov(eax, FieldOperand(eax, String::kLengthOffset));

[danno, 2011/07/21 12:39:07]

eax -> tos_?

[Sven Panne, 2011/07/21 13:49:28]

Ooops, fixed, same for Smi part above.

+    __ ret(1 * kPointerSize);  // the string length is OK as the return value
+    __ bind(&not_string);
+  } else if (types_.Contains(INTERNAL_OBJECT)) {
+    // We've seen a string for the first time -> patch
+    __ CmpInstanceType(map, FIRST_NONSTRING_TYPE);
+    __ j(below, &patch, Label::kNear);
+  }
+
+  if (types_.Contains(HEAP_NUMBER)) {
+    // heap number -> false iff +0, -0, or NaN.
+    Label not_heap_number, false_result;
+    __ cmp(map, factory->heap_number_map());
+    __ j(not_equal, &not_heap_number, Label::kNear);
+    __ fldz();
+    __ fld_d(FieldOperand(eax, HeapNumber::kValueOffset));
+    __ FCmp();
+    __ j(zero, &false_result, Label::kNear);
+    __ mov(tos_, 1);
+    __ ret(1 * kPointerSize);
+    __ bind(&false_result);
+    __ xor_(tos_, Operand(tos_));
+    __ ret(1 * kPointerSize);
+    __ bind(&not_heap_number);
+  } else if (types_.Contains(INTERNAL_OBJECT)) {
+    // We've seen a heap number for the first time -> patch
+    __ cmp(map, factory->heap_number_map());
+    __ j(equal, &patch, Label::kNear);
+  }
+
+  if (types_.Contains(INTERNAL_OBJECT)) {

[fschneider, 2011/07/21 13:16:44]

Can you explain why we need the INTERNAL_OBJECT case?

[Sven Panne, 2011/07/21 13:49:28]

While we probably can't encounter internal objects at "normal" runtime (at least
I think so), they *do* occur at v8 startup, e.g. object/function templates etc.

+    // internal objects -> true
+    __ mov(tos_, 1);
+    __ ret(1 * kPointerSize);
+  }
+
+  __ bind(&patch);
+  GenerateTypeTransition(masm);
 }
 
 
+void ToBooleanStub::CheckOddball(MacroAssembler* masm,
+                                 Type type,
+                                 Handle<Object> value,
+                                 bool result,
+                                 Label* patch) {
+  __ cmp(eax, value);

[danno, 2011/07/21 12:39:07]

This should be duplicated in the two if branches so that the else at the bottom
doesn't generate a spurious cmp.

[Sven Panne, 2011/07/21 13:49:28]

Done.

+  if (types_.Contains(type)) {
+    // If we see an expected oddball, return its ToBoolean value tos_.
+    Label different_value;
+    __ j(not_equal, &different_value, Label::kNear);
+    if (result) {
+      __ mov(tos_, 1);
+    } else {
+      __ xor_(tos_, Operand(tos_));
+    }
+    __ ret(1 * kPointerSize);
+    __ bind(&different_value);
+  } else if (types_.Contains(INTERNAL_OBJECT)) {
+    // If we see an unexpected oddball and handle internal objects, we must
+    // patch because the code for internal objects doesn't handle it explictly.
+    __ j(equal, patch);
+  }
+}
+
+
+void ToBooleanStub::GenerateTypeTransition(MacroAssembler* masm) {
+  __ pop(ecx);  // Get return address, operand is now on top of stack.
+  __ push(Immediate(Smi::FromInt(tos_.code())));
+  __ push(Immediate(Smi::FromInt(types_.ToInt())));
+  __ push(ecx);  // Push return address.
+  // Patch the caller to an appropriate specialized stub and return the
+  // operation result to the caller of the stub.
+  __ TailCallExternalReference(
+      ExternalReference(IC_Utility(IC::kToBoolean_Patch), masm->isolate()),
+      3,
+      1);
+}
+
+
 class FloatingPointHelper : public AllStatic {
  public:
   enum ArgLocation {