A64: Truncate booleans to 0 or 1 in LTaggedToI.

src/a64/lithium-codegen-a64.cc

Index: src/a64/lithium-codegen-a64.cc
diff --git a/src/a64/lithium-codegen-a64.cc b/src/a64/lithium-codegen-a64.cc
index 3a58f021e4b7c1115906e7957105b01a27e4f62d..bbbd05f9c2e6de542690448102b937916426b6ef 100644
--- a/src/a64/lithium-codegen-a64.cc
+++ b/src/a64/lithium-codegen-a64.cc
@@ -5118,7 +5118,7 @@ void LCodeGen::DoDeferredTaggedToI(LTaggedToI* instr,
   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);
@@ -5129,12 +5129,17 @@ void LCodeGen::DoDeferredTaggedToI(LTaggedToI* instr,
     __ 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());