Implement type recording for ToBoolean on ARM.

src/arm/code-stubs-arm.cc

 // Copyright 2011 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 1585 matching lines @@
     __ mov(r0, Operand(Smi::FromInt(ncr)));
     __ push(r0);
   }
 
   // Call the native; it returns -1 (less), 0 (equal), or 1 (greater)
   // tagged as a small integer.
   __ InvokeBuiltin(native, JUMP_FUNCTION);
 }
 
 
-// The stub returns zero for false, and a non-zero value for true.
+// The stub expects its argument in the tos_ register and returns its result in
+// it, too: zero for false, and a non-zero value for true.
 void ToBooleanStub::Generate(MacroAssembler* masm) {
   // This stub uses VFP3 instructions.
   CpuFeatures::Scope scope(VFP3);
 
-  Label false_result, true_result, not_string;
+  Label patch;
   const Register map = r9.is(tos_) ? r7 : r9;

[Erik Corry, 2011/08/05 12:50:46]

If we have ever seen an internal object you could start with a Smi check and an
internal object check here.  Then you could remove the special handling for
internal object on the other 10 cases.  It would be slightly slower for the
internal object case, but that is rare and arguably broken anyway.  It would
simplify things a lot.

[Sven Panne, 2011/08/09 07:58:21]

I think we can get rid of all internal object checks when we change
apinatives.js slightly. But this is platform-independent, so let's handle this
in a separate CL.

 
   // undefined -> false

[Erik Corry, 2011/08/05 12:50:46]

Missing full stops on the end of comments several places.  Not your fault, but
we might as well fix it now that we are looking at the code.

[Sven Panne, 2011/08/09 07:58:21]

Done.

-  __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
-  __ cmp(tos_, ip);
-  __ b(eq, &false_result);
+  CheckOddball(masm, UNDEFINED, Heap::kUndefinedValueRootIndex, false, &patch);
 
   // Boolean -> its value
-  __ LoadRoot(ip, Heap::kFalseValueRootIndex);
-  __ cmp(tos_, ip);
-  __ b(eq, &false_result);
-  __ LoadRoot(ip, Heap::kTrueValueRootIndex);
-  __ cmp(tos_, ip);
-  // "tos_" is a register and contains a non-zero value.  Hence we implicitly
-  // return true if the equal condition is satisfied.
-  __ Ret(eq);
+  CheckOddball(masm, BOOLEAN, Heap::kFalseValueRootIndex, false, &patch);
+  CheckOddball(masm, BOOLEAN, Heap::kTrueValueRootIndex, true, &patch);
 
-  // Smis: 0 -> false, all other -> true
-  __ tst(tos_, tos_);
-  __ b(eq, &false_result);
-  __ tst(tos_, Operand(kSmiTagMask));
-  // "tos_" is a register and contains a non-zero value.  Hence we implicitly
-  // return true if the not equal condition is satisfied.
-  __ Ret(eq);
+  // 'null' -> false.
+  CheckOddball(masm, NULL_TYPE, Heap::kNullValueRootIndex, false, &patch);
 
-  // 'null' -> false
-  __ LoadRoot(ip, Heap::kNullValueRootIndex);
-  __ cmp(tos_, ip);
-  __ b(eq, &false_result);
+  if (types_.Contains(SMI)) {
+    // Smis: 0 -> false, all other -> true
+    __ tst(tos_, Operand(kSmiTagMask));
+    // tos_ contains the correct return value already
+    __ Ret(eq);
+  } else if (types_.NeedsMap()) {
+    // If we need a map later and have a Smi -> patch.
+    __ JumpIfSmi(tos_, &patch);
+  }
 
-  // Get the map of the heap object.
-  __ ldr(map, FieldMemOperand(tos_, HeapObject::kMapOffset));
+  if (types_.NeedsMap()) {
+    __ ldr(map, FieldMemOperand(tos_, HeapObject::kMapOffset));
 
-  // Undetectable -> false.
-  __ ldrb(ip, FieldMemOperand(map, Map::kBitFieldOffset));
-  __ tst(ip, Operand(1 << Map::kIsUndetectable));
-  __ b(&false_result, ne);
+    // Everything with a map could be undetectable, so check this now.

[Erik Corry, 2011/08/05 12:50:46]

Pretty sure that it is just strings and JSObjects.  The tests will catch it if I
am wrong, at least they will if they run everything twice, one to patch the
ToBooleanStub and the second time to run it.

[Sven Panne, 2011/08/09 07:58:21]

Again, this is platform-independent, so let's handle this in a separate CL.

+    __ ldrb(ip, FieldMemOperand(map, Map::kBitFieldOffset));
+    __ tst(ip, Operand(1 << Map::kIsUndetectable));
+    // Undetectable -> false.
+    __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, ne);
+    __ Ret(ne);
+  }
 
-  // JavaScript object -> true.
-  __ CompareInstanceType(map, ip, FIRST_SPEC_OBJECT_TYPE);
-  // "tos_" is a register and contains a non-zero value. Hence we implicitly
-  // return true if the greater than condition is satisfied.
-  __ Ret(ge);
+  if (types_.Contains(SPEC_OBJECT)) {
+    // spec object -> true.
+    __ CompareInstanceType(map, ip, FIRST_SPEC_OBJECT_TYPE);
+    // tos_ contains the correct non-zero return value already.
+    __ Ret(ge);
+  } else if (types_.Contains(INTERNAL_OBJECT)) {
+    // We've seen a spec object for the first time -> patch.
+    __ CompareInstanceType(map, ip, FIRST_SPEC_OBJECT_TYPE);
+    __ b(ge, &patch);
+  }
 
-  // String value -> false iff empty.
+  if (types_.Contains(STRING)) {
+    // String value -> false iff empty.
   __ CompareInstanceType(map, ip, FIRST_NONSTRING_TYPE);
-  __ b(&not_string, ge);
-  __ ldr(tos_, FieldMemOperand(tos_, String::kLengthOffset));
-  // Return string length as boolean value, i.e. return false iff length is 0.
-  __ Ret();
+  __ ldr(tos_, FieldMemOperand(tos_, String::kLengthOffset), lt);
+  __ Ret(lt);  // the string length is OK as the return value
+  } else if (types_.Contains(INTERNAL_OBJECT)) {
+    // We've seen a string for the first time -> patch
+    __ CompareInstanceType(map, ip, FIRST_NONSTRING_TYPE);
+    __ b(lt, &patch);
+  }
 
-  __ bind(&not_string);
-  // HeapNumber -> false iff +0, -0, or NaN.
-  __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
-  __ b(&true_result, ne);
-  __ vldr(d1, FieldMemOperand(tos_, HeapNumber::kValueOffset));
-  __ VFPCompareAndSetFlags(d1, 0.0);
-  // "tos_" is a register, and contains a non zero value by default.
-  // Hence we only need to overwrite "tos_" with zero to return false for
-  // FP_ZERO or FP_NAN cases. Otherwise, by default it returns true.
-  __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, eq);  // for FP_ZERO
-  __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, vs);  // for FP_NAN
-  __ Ret();
+  if (types_.Contains(HEAP_NUMBER)) {
+    // heap number -> false iff +0, -0, or NaN.
+    Label not_heap_number;
+    __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
+    __ b(ne, &not_heap_number);
+    __ vldr(d1, FieldMemOperand(tos_, HeapNumber::kValueOffset));
+    __ VFPCompareAndSetFlags(d1, 0.0);
+    // "tos_" is a register, and contains a non zero value by default.
+    // Hence we only need to overwrite "tos_" with zero to return false for
+    // FP_ZERO or FP_NAN cases. Otherwise, by default it returns true.
+    __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, eq);  // for FP_ZERO
+    __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, vs);  // for FP_NAN
+    __ Ret();
+    __ bind(&not_heap_number);
+  } else if (types_.Contains(INTERNAL_OBJECT)) {
+    // We've seen a heap number for the first time -> patch
+    __ CompareRoot(map, Heap::kHeapNumberMapRootIndex);
+    __ b(eq, &patch);
+  }
 
-  // Return 1/0 for true/false in tos_.
-  __ bind(&true_result);
-  __ mov(tos_, Operand(1, RelocInfo::NONE));
-  __ Ret();
-  __ bind(&false_result);
-  __ mov(tos_, Operand(0, RelocInfo::NONE));
-  __ Ret();
+  if (types_.Contains(INTERNAL_OBJECT)) {
+    // internal objects -> true

[Erik Corry, 2011/08/05 12:50:46]

Caps and full stop.

[Sven Panne, 2011/08/09 07:58:21]

Done.

+    __ mov(tos_, Operand(1, RelocInfo::NONE));
+    __ Ret();
+  }
+
+  if (!types_.IsAll()) {
+    __ bind(&patch);
+    GenerateTypeTransition(masm);
+  }
+}
+
+
+void ToBooleanStub::CheckOddball(MacroAssembler* masm,
+                                 Type type,
+                                 Heap::RootListIndex value,
+                                 bool result,
+                                 Label* patch) {
+  if (types_.Contains(type)) {
+    // If we see an expected oddball, return its ToBoolean value tos_.
+    __ LoadRoot(ip, value);
+    __ cmp(tos_, ip);
+    // The value of a root is never NULL, so we can avoid loading a non-null
+    // value into tos_ when we want to return 'true'.
+    if (!result) {
+      __ mov(tos_, Operand(0, RelocInfo::NONE), LeaveCC, eq);
+    }
+    __ Ret(eq);
+  } 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.
+    __ LoadRoot(ip, value);
+    __ cmp(tos_, ip);
+    __ b(eq, patch);
+  }
+}
+
+
+void ToBooleanStub::GenerateTypeTransition(MacroAssembler* masm) {
+  if (!tos_.is(r3)) {
+    __ mov(r3, Operand(tos_));
+  }
+  __ mov(r2, Operand(Smi::FromInt(tos_.code())));
+  __ mov(r1, Operand(Smi::FromInt(types_.ToByte())));
+  __ Push(r3, r2, r1);
+  // 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);
 }
 
 
 void UnaryOpStub::PrintName(StringStream* stream) {
   const char* op_name = Token::Name(op_);
   const char* overwrite_name = NULL;  // Make g++ happy.
   switch (mode_) {
     case UNARY_NO_OVERWRITE: overwrite_name = "Alloc"; break;
     case UNARY_OVERWRITE: overwrite_name = "Overwrite"; break;
   }
@@ skipping 4842 matching lines @@
   __ mov(result, Operand(0));
   __ Ret();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM