Canonicalize NaNs on store to Fast(Float|Double) arrays

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 9b96cfe7ca6a1dcd19ef7394a001c60e6863b84c..cff5070bbcf6b275886ed5512b5ec5602cc2d951 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -2590,6 +2590,10 @@ bool HLoadKeyed::UsesMustHandleHole() const {
     return false;
   }
 
+  if (IsExternalArrayElementsKind(elements_kind())) {
+    return false;
+  }
+
   if (hole_mode() == ALLOW_RETURN_HOLE) return true;
 
   if (IsFastDoubleElementsKind(elements_kind())) {
@@ -2612,6 +2616,10 @@ bool HLoadKeyed::RequiresHoleCheck() const {
     return false;
   }
 
+  if (IsExternalArrayElementsKind(elements_kind())) {
+    return false;
+  }
+
   return !UsesMustHandleHole();
 }
 
@@ -3037,10 +3045,22 @@ bool HStoreKeyed::NeedsCanonicalization() {
   // If value is an integer or smi or comes from the result of a keyed load or
   // constant then it is either be a non-hole value or in the case of a constant
   // the hole is only being stored explicitly: no need for canonicalization.
-  if (value()->IsLoadKeyed() || value()->IsConstant()) {
+  //
+  // The exception to that is keyed loads from external float or double arrays:
+  // these can load arbitrary representation of NaN.
+
+  if (value()->IsConstant()) {
     return false;
   }
 
+  if (value()->IsLoadKeyed()) {
+    ElementsKind load_elements_kind =
+        HLoadKeyed::cast(value())->elements_kind();
+
+    return load_elements_kind == EXTERNAL_FLOAT_ELEMENTS

[danno, 2013/03/28 12:30:40]

Maybe add a predicate to elements-kind.h: IsExternalFloatOrDoubleElementsKind?

+        || load_elements_kind == EXTERNAL_DOUBLE_ELEMENTS;
+  }
+
   if (value()->IsChange()) {
     if (HChange::cast(value())->from().IsInteger32()) {
       return false;