Bug 1114064. Support AliasNone DOM methods in ion compilation. r=efaust

js/src/jit/MIR.cpp

@@ -1013,11 +1013,10 @@ MCallDOMNative::getAliasSet() const
 {
     const JSJitInfo *jitInfo = getJitInfo();
 
-    MOZ_ASSERT(jitInfo->aliasSet() != JSJitInfo::AliasNone);
     // If we don't know anything about the types of our arguments, we have to
     // assume that type-coercions can have side-effects, so we need to alias
     // everything.
-    if (jitInfo->aliasSet() != JSJitInfo::AliasDOMSets || !jitInfo->isTypedMethodJitInfo())
+    if (jitInfo->aliasSet() == JSJitInfo::AliasEverything || !jitInfo->isTypedMethodJitInfo())
         return AliasSet::Store(AliasSet::Any);
 
     uint32_t argIndex = 0;
@@ -1048,8 +1047,12 @@ MCallDOMNative::getAliasSet() const
          }
     }
 
-    // We checked all the args, and they check out.  So we only
-    // alias DOM mutations.
+    // We checked all the args, and they check out.  So we only alias DOM
+    // mutations or alias nothing, depending on the alias set in the jitinfo.
+    if (jitInfo->aliasSet() == JSJitInfo::AliasNone)
+        return AliasSet::None();
+
+    MOZ_ASSERT(jitInfo->aliasSet() == JSJitInfo::AliasDOMSets);
     return AliasSet::Load(AliasSet::DOMProperty);
 }
 

js/src/jit/MIR.h

@@ -3366,11 +3366,11 @@ class MCallDOMNative : public MCall
         : MCall(target, numActualArgs, false)
     {
         // If our jitinfo is not marked movable, that means that our C++
-        // implementation is fallible or that we have no hope of ever doing the
-        // sort of argument analysis that would allow us to detemine that we're
-        // side-effect-free.  In the latter case we wouldn't get DCEd no matter
-        // what, but for the former case we have to explicitly say that we can't
-        // be DCEd.
+        // implementation is fallible or that it never wants to be eliminated or
+        // coalesced or that we have no hope of ever doing the sort of argument
+        // analysis that would allow us to detemine that we're side-effect-free.
+        // In the latter case we wouldn't get DCEd no matter what, but for the
+        // former two cases we have to explicitly say that we can't be DCEd.
         if (!getJitInfo()->isMovable)
             setGuard();
     }