A64: Truncate booleans to 0 or 1 in LTaggedToI.

src/a64/lithium-codegen-a64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
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@@ skipping 5100 matching lines @@
   DoubleRegister dbl_scratch1 = double_scratch();
 
   Label done;
 
   // Load heap object map.
   __ Ldr(scratch1, FieldMemOperand(input, HeapObject::kMapOffset));
 
   if (instr->truncating()) {
     Register output = ToRegister(instr->result());
     Register scratch2 = ToRegister(temp2);
-    Label check_bools, undefined;
+    Label check_bools, check_false, check_undefined;
 
     // If it's not a heap number, jump to undefined check.
     __ JumpIfNotRoot(scratch1, Heap::kHeapNumberMapRootIndex, &check_bools);
 
     // A heap number: load value and convert to int32 using truncating function.
     __ Ldr(dbl_scratch1, FieldMemOperand(input, HeapNumber::kValueOffset));
     __ ECMA262ToInt32(output, dbl_scratch1, scratch1, scratch2);
     __ B(&done);
 
     __ Bind(&check_bools);
-
-    TODO_UNIMPLEMENTED("LTaggedToI: Truncate booleans to 0 or 1.");
+    __ JumpIfNotRoot(scratch1, Heap::kTrueValueRootIndex, &check_false);

[m.m.capewell, 2014/02/05 18:43:23]

It may be better to load both roots at once and use conditional instructions.

Register true_root = output;
Register false_root = scratch2;
LoadTrueFalseRoots(true_root, false_root);
Cmp(scratch1, true_root);
Cset(output, eq);
Ccmp(scratch1, false_root, ZFlag, ne);
B(eq, &done);
// Fall through to check_undefined.

You can delete the Mov(output, 0) from check_undefined, if it can't be reached
from elsewhere.

[ulan, 2014/02/05 19:21:29]

Nice! Done.

+    __ Mov(output, 1);
+    __ B(&done);
+    __ Bind(&check_false);
+    __ JumpIfNotRoot(scratch1, Heap::kFalseValueRootIndex, &check_undefined);
+    __ Mov(output, 0);
+    __ B(&done);
 
     // Check for undefined. Undefined is converted to zero for truncating
     // conversions.
-    __ Bind(&undefined);
+    __ Bind(&check_undefined);
 
     DeoptimizeIfNotRoot(input, Heap::kUndefinedValueRootIndex,
                         instr->environment());
     __ Mov(output, 0);
   } else {
     Register output = ToRegister32(instr->result());
 
     DoubleRegister dbl_scratch2 = ToDoubleRegister(temp2);
     Label converted;
 
@@ skipping 396 matching lines @@
   __ Bind(&out_of_object);
   __ Ldr(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
   // Index is equal to negated out of object property index plus 1.
   __ Sub(result, result, Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(result, FieldMemOperand(result,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ Bind(&done);
 }
 
 } }  // namespace v8::internal