Bug 1118978 part 1. Introduce "Affects" and "DependsOn" state for IDL attributes and operations and desugar [Pure] and [Constant] into that state. r=peterv

This does not change the generated binding code in any way for our existing IDL files.

dom/bindings/Codegen.py

@@ -10,7 +10,7 @@ import string
 import math
 import textwrap
 
-from WebIDL import BuiltinTypes, IDLBuiltinType, IDLNullValue, IDLSequenceType, IDLType, IDLAttribute, IDLUndefinedValue, IDLEmptySequenceValue, IDLDictionary
+from WebIDL import BuiltinTypes, IDLBuiltinType, IDLNullValue, IDLSequenceType, IDLType, IDLAttribute, IDLInterfaceMember, IDLUndefinedValue, IDLEmptySequenceValue, IDLDictionary
 from Configuration import NoSuchDescriptorError, getTypesFromDescriptor, getTypesFromDictionary, getTypesFromCallback, getAllTypes, Descriptor
 
 AUTOGENERATED_WARNING_COMMENT = \
@@ -2114,8 +2114,7 @@ def clearableCachedAttrs(descriptor):
     return (m for m in descriptor.interface.members if
             m.isAttr() and
             # Constants should never need clearing!
-            not m.getExtendedAttribute("Constant") and
-            not m.getExtendedAttribute("SameObject") and
+            m.dependsOn != "Nothing" and
             m.slotIndex is not None)
 
 def MakeClearCachedValueNativeName(member):
@@ -8080,16 +8079,9 @@ class CGMemberJITInfo(CGThing):
             getter = ("(JSJitGetterOp)get_%s" %
                       IDLToCIdentifier(self.member.identifier.name))
             getterinfal = "infallible" in self.descriptor.getExtendedAttributes(self.member, getter=True)
-            getterconst = (self.member.getExtendedAttribute("SameObject") or
-                           self.member.getExtendedAttribute("Constant"))
-            getterpure = getterconst or self.member.getExtendedAttribute("Pure")
-            if getterconst:
-                aliasSet = "AliasNone"
-            elif getterpure:
-                aliasSet = "AliasDOMSets"
-            else:
-                aliasSet = "AliasEverything"
-            movable = getterpure and getterinfal
+
+            movable = self.mayBeMovable() and getterinfal
+            aliasSet = self.aliasSet()
 
             getterinfal = getterinfal and infallibleForMember(self.member, self.member.type, self.descriptor)
             isAlwaysInSlot = self.member.getExtendedAttribute("StoreInSlot")
@@ -8134,7 +8126,6 @@ class CGMemberJITInfo(CGThing):
                 name = CGMethodPromiseWrapper.makeName(name)
             # Actually a JSJitMethodOp, but JSJitGetterOp is first in the union.
             method = ("(JSJitGetterOp)%s" % name)
-            methodPure = self.member.getExtendedAttribute("Pure")
 
             # Methods are infallible if they are infallible, have no arguments
             # to unwrap, and have a return type that's infallible to wrap up for
@@ -8148,13 +8139,13 @@ class CGMemberJITInfo(CGThing):
                 movable = False
             else:
                 sig = sigs[0]
-                # For pure methods, it's OK to set movable to our notion of
-                # infallible on the C++ side, without considering argument
-                # conversions, since argument conversions that can reliably
-                # throw would be effectful anyway and the jit doesn't move
-                # effectful things.
+                # For methods that affect nothing, it's OK to set movable to our
+                # notion of infallible on the C++ side, without considering
+                # argument conversions, since argument conversions that can
+                # reliably throw would be effectful anyway and the jit doesn't
+                # move effectful things.
                 hasInfallibleImpl = "infallible" in self.descriptor.getExtendedAttributes(self.member)
-                movable = methodPure and hasInfallibleImpl
+                movable = self.mayBeMovable() and hasInfallibleImpl
                 # XXXbz can we move the smarts about fallibility due to arg
                 # conversions into the JIT, using our new args stuff?
                 if (len(sig[1]) != 0 or
@@ -8163,16 +8154,13 @@ class CGMemberJITInfo(CGThing):
                     methodInfal = False
                 else:
                     methodInfal = hasInfallibleImpl
-                # For now, only bother to output args if we're pure
-                if methodPure:
+                # For now, only bother to output args if we're side-effect-free.
+                if self.member.affects == "Nothing":
                     args = sig[1]
                 else:
                     args = None
 
-            if args is not None:
-                aliasSet = "AliasDOMSets"
-            else:
-                aliasSet = "AliasEverything"
+            aliasSet = self.aliasSet()
             result = self.defineJitInfo(methodinfo, method, "Method",
                                         methodInfal, movable, aliasSet,
                                         False, False, "0",
@@ -8180,6 +8168,37 @@ class CGMemberJITInfo(CGThing):
             return result
         raise TypeError("Illegal member type to CGPropertyJITInfo")
 
+    def mayBeMovable(self):
+        """
+        Returns whether this attribute or method may be movable, just
+        based on Affects/DependsOn annotations.
+        """
+        affects = self.member.affects
+        dependsOn = self.member.dependsOn
+        assert affects in IDLInterfaceMember.AffectsValues
+        assert dependsOn in IDLInterfaceMember.DependsOnValues
+        return affects == "Nothing" and dependsOn != "Everything"
+
+    def aliasSet(self):
+        """Returns the alias set to store in the jitinfo.  This may not be the
+        effective alias set the JIT uses, depending on whether we have enough
+        information about our args to allow the JIT to prove that effectful
+        argument conversions won't happen.
+
+        """
+        dependsOn = self.member.dependsOn
+        assert dependsOn in IDLInterfaceMember.DependsOnValues
+
+        if dependsOn == "Nothing":
+            assert self.member.affects == "Nothing"
+            return "AliasNone"
+
+        if dependsOn == "DOMState":
+            assert self.member.affects == "Nothing"
+            return "AliasDOMSets"
+
+        return "AliasEverything"
+
     @staticmethod
     def getJSReturnTypeTag(t):
         if t.nullable():

dom/bindings/parser/WebIDL.py

@@ -3043,6 +3043,9 @@ class IDLInterfaceMember(IDLObjectWithIdentifier):
         'Stringifier'
     )
 
+    AffectsValues = ("Nothing", "Everything")
+    DependsOnValues = ("Nothing", "DOMState", "Everything")
+
     def __init__(self, location, identifier, tag):
         IDLObjectWithIdentifier.__init__(self, location, None, identifier)
         self.tag = tag
@@ -3097,6 +3100,22 @@ class IDLInterfaceMember(IDLObjectWithIdentifier):
                               self._scope.primaryGlobalName,
                               [self.location])
 
+    def _setDependsOn(self, dependsOn):
+        if self.dependsOn != "Everything":
+            raise WebIDLError("Trying to specify multiple different "
+                              "Pure, or Constant extended attributes for "
+                              "attribute", [self.location])
+        assert dependsOn in IDLInterfaceMember.DependsOnValues:
+        self.dependsOn = dependsOn
+
+    def _setAffects(self, affects):
+        if self.affects != "Everything":
+            raise WebIDLError("Trying to specify multiple different "
+                              "Pure, or Constant extended attributes for "
+                              "attribute", [self.location])
+        assert affects in IDLInterfaceMember.AffectsValues:
+        self.affects = affects
+
 class IDLConst(IDLInterfaceMember):
     def __init__(self, location, identifier, type, value):
         IDLInterfaceMember.__init__(self, location, identifier,
@@ -3175,6 +3194,8 @@ class IDLAttribute(IDLInterfaceMember):
         self.enforceRange = False
         self.clamp = False
         self.slotIndex = None
+        self.dependsOn = "Everything"
+        self.affects = "Everything"
 
         if static and identifier.name == "prototype":
             raise WebIDLError("The identifier of a static attribute must not be 'prototype'",
@@ -3243,10 +3264,9 @@ class IDLAttribute(IDLInterfaceMember):
 
         if ((self.getExtendedAttribute("Cached") or
              self.getExtendedAttribute("StoreInSlot")) and
-            not self.getExtendedAttribute("Constant") and
-            not self.getExtendedAttribute("Pure")):
+            not self.affects == "Nothing"):
             raise WebIDLError("Cached attributes and attributes stored in "
-                              "slots must be constant or pure, since the "
+                              "slots must be Constant or Pure, since the "
                               "getter won't always be called.",
                               [self.location])
         if self.getExtendedAttribute("Frozen"):
@@ -3372,14 +3392,23 @@ class IDLAttribute(IDLInterfaceMember):
                                   [attr.location, self.location])
         elif identifier == "Exposed":
             convertExposedAttrToGlobalNameSet(attr, self._exposureGlobalNames)
+        elif identifier == "Pure":
+            if not attr.noArguments():
+                raise WebIDLError("[Pure] must take no arguments",
+                                  [attr.location])
+            self._setDependsOn("DOMState")
+            self._setAffects("Nothing")
+        elif identifier == "Constant" or identifier == "SameObject":
+            if not attr.noArguments():
+                raise WebIDLError("[%s] must take no arguments" % identifier,
+                                  [attr.location])
+            self._setDependsOn("Nothing")
+            self._setAffects("Nothing")
         elif (identifier == "Pref" or
               identifier == "SetterThrows" or
-              identifier == "Pure" or
               identifier == "Throws" or
               identifier == "GetterThrows" or
               identifier == "ChromeOnly" or
-              identifier == "SameObject" or
-              identifier == "Constant" or
               identifier == "Func" or
               identifier == "Frozen" or
               identifier == "AvailableIn" or
@@ -3663,6 +3692,8 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
         self._jsonifier = jsonifier
         self._specialType = specialType
         self._unforgeable = False
+        self.dependsOn = "Everything"
+        self.affects = "Everything"
 
         if static and identifier.name == "prototype":
             raise WebIDLError("The identifier of a static operation must not be 'prototype'",
@@ -3974,13 +4005,18 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
                                   [attr.location, self.location])
         elif identifier == "Exposed":
             convertExposedAttrToGlobalNameSet(attr, self._exposureGlobalNames)
-        elif (identifier == "Pure" or
-              identifier == "CrossOriginCallable" or
+        elif (identifier == "CrossOriginCallable" or
               identifier == "WebGLHandlesContextLoss"):
             # Known no-argument attributes.
             if not attr.noArguments():
                 raise WebIDLError("[%s] must take no arguments" % identifier,
                                   [attr.location])
+        elif identifier == "Pure":
+            if not attr.noArguments():
+                raise WebIDLError("[Pure] must take no arguments",
+                                  [attr.location])
+            self._setDependsOn("DOMState")
+            self._setAffects("Nothing")
         elif (identifier == "Throws" or
               identifier == "NewObject" or
               identifier == "ChromeOnly" or