Prevent deopt on double value assignment to typed arrays

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 38aa8f8260b414b836c3d25dfa54d5edf8b4b0b3..668e0a9159925431113bad2d0f10efc59ff38bed 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -1767,6 +1767,32 @@ LInstruction* LChunkBuilder::DoClampToUint8(HClampToUint8* instr) {
 }
 
 
+LInstruction* LChunkBuilder::DoToInt32(HToInt32* instr) {
+  HValue* value = instr->value();
+  Representation input_rep = value->representation();
+  LOperand* reg = UseRegister(value);
+  if (input_rep.IsDouble()) {
+      LDoubleToI* res = new LDoubleToI(reg,

[Kevin Millikin (Chromium), 2011/05/26 07:53:37]

Two space indent here.

I'd name the two TempRegisters.  There is some dependence on the order uses are
communicated to the register allocator.  The use at this site is OK (right now),
but it would be better to have:

LOperand* temp1 = TempRegister();
LOperand* temp2 = TempRegister();
LDoubleToI* res = new LDoubleToI(reg, temp1, temp2);

if for no other reason than it is deterministic across compilers.

You can probably hoist temp1 and temp2 out of the if.

[danno, 2011/06/01 13:14:41]

Done.

+                                       TempRegister(),
+                                       TempRegister());
+      return AssignEnvironment(DefineAsRegister(res));
+  } else if (input_rep.IsInteger32()) {
+    // Canonicalization should already have removed the hydrogen instruction in
+    // this case, since it is a noop.
+    UNREACHABLE();
+    return NULL;
+  } else {
+    ASSERT(input_rep.IsTagged());
+    LOperand* temp1 = TempRegister();
+    LOperand* temp2 = TempRegister();
+    LOperand* temp3 = FixedTemp(d3);
+    LInstruction* res = DefineSameAsFirst(

[Kevin Millikin (Chromium), 2011/05/26 07:53:37]

I like

LTaggedToI* res = new LTaggedToI(reg, temp1, temp2, temp3);
return AssigneEnvironment(DefineSameAsFirst(res));

better.  It's consistent with the first clause and avoids the line break :)

[danno, 2011/06/01 13:14:41]

Done.

+        new LTaggedToI(reg, temp1, temp2, temp3));
+    return AssignEnvironment(res);
+  }
+}
+
+
 LInstruction* LChunkBuilder::DoReturn(HReturn* instr) {
   return new LReturn(UseFixed(instr->value(), r0));
 }