2008-06-20 Marek Safar <marek.safar@gmail.com>

[mono.git] / mcs / mcs / TODO

diff --git a/mcs/mcs/TODO b/mcs/mcs/TODO
index c6ec5c3e359dd186736d6f49c45bfd89a2317e6e..741e63d2ab8cd6201491913c3bda9e15d599fee2 100644 (file)
--- a/mcs/mcs/TODO
+++ b/mcs/mcs/TODO
@@ -1,182 +1,126 @@
+Iterators
+=========

 
 

-Notes on memory allocation
---------------------------

 
 

-       A run of the AllocationProfile shows that the compiler allocates roughly
-       30 megabytes of strings.  From those, 20 megabytes come from
-       LookupType.  
+       Ok, solved part of the problem, but not the second.

 
 

-       See the notes on current_container problems below on memory usage.  
+       Apparently there are 2 scopes in test-iter-05.cs that
+       are referenced, but when we call "ComputeMethodHost" in
+       iterators.cs:854 this information is not yet available.

 
 

-GetNamespaces
--------------
-
-       Obtaining the list of namespaces is an expensive process because
-       Reflection.Emit does not provide a quick way of pulling the data out,
-       and it is too slow to load it.
-
-       Calling GetNamespaces on my machine (1Ghz):
-
-               * Takes half a second with the standard assemblies (corlib + System);
-                 Fetching the types from it takes 0.0028650 seconds. 
-
-               * Loading the top 10 largest assemblies we ship with Mono makes MCS take 
-                 8 seconds to startup the first time, subsequent invocations take 2 seconds.
-
-                 Fetching all the types (Assembly.GetTypes ()) for all the assemblies takes
-                 0.0069170 seconds.
-
-       So pulling all the types takes very little time, maybe we should look into our
-       Hashtable implementation to make it more optimal.
+===========================================

 
 

-       This prohibits re-writting SimpleName to take advantage of
-       knowing the namespace names in advance.  Knowing the namespaces in advance
-       would allow me to reduce the guesswork in which we are currently engaged
-       to find a type definition.
+* Value Parameter

 
 

-LookupTypeReflection:
----------------------
+       I believe that `Value Parameter' might have been introduced
+       after C# 1.0, also notice than in the treatment of Value Parameter
+       the parameters are defined in four categories:

 
 

-       With something like `System.Object', LookupTypeReflection will be called
-       twice: once to find out that `System' is not a type and once
-       for System.Object.
+       Section 9.3 in the latest spec.

 
 

-       This is required because System.Reflection requires that the type/nested types are
-       not separated by a dot but by a plus sign.

 
 

-       A nested class would be My+Class (My being the toplevel, Class the nested one).
+Large project:
+--------------

 
 

-       It is interesting to look at the most called lookups when bootstrapping MCS:
+New
+---

 
 

-    647        LTR: ArrayList
-    713        LTR: System.Globalization
-    822        LTR: System.Object+Expression
-    904        LTR: Mono.CSharp.ArrayList
-    976        LTR: System.Runtime.CompilerServices
-    999        LTR: Type
-   1118        LTR: System.Runtime
-   1208        LTR: Mono.CSharp.Type
-   1373        LTR: Mono.Languages
-   1599        LTR: System.Diagnostics
-   2036        LTR: System.Text
-   2302        LTR: System.Reflection.Emit
-   2515        LTR: System.Collections
-   4527        LTR: System.Reflection
-  22273        LTR: Mono.CSharp
-  24245        LTR: System
-  27005        LTR: Mono
+       It would be nice to optimize the case of:

 
 

-       Analysis:
-               The top 9 lookups are done for things which are not types.
+               Method (new ValueType ())

 
 

-               Mono.CSharp.Type happens to be a common lookup: the class Type
-               used heavily in the compiler in the default namespace.
+       So that no temporary is created, and we only use a newobj call
+       that remains on the stack, as opposed to ldloca, initobj, ldloc
+       call.

 
 

-               RED FLAG:
+NEW NOTES:
+----------

 
 

-               Then `Type' is looked up alone a lot of the time, this happens
-               in parameter declarations and am not entirely sure that this is
-               correct (FindType will pass to LookupInterfaceOrClass a the current_type.FullName,
-               which for some reason is null!).  This seems to be a problem with a lost
-               piece of context during FindType.
+       ImplicitStandardConversionExists and ImplicitStandardConversion
+       should always be the same, but there are a few diverging lines that
+       must be studied:

 
 

-               System.Object is also used a lot as a toplevel class, and we assume it will
-               have children, we should just shortcut this.
+                       if (expr_type == target_type && !(expr is NullLiteral))
+                               return expr;

 
 

-    A cache:
+       vs:

 
 

-       Adding a cache and adding a catch for `System.Object' to flag that it wont be the
-       root of a hierarchy reduced the MCS bootstrap time from 10.22 seconds to 8.90 seconds.
+                       if (expr_type == target_type)
+                               return true;

 
 

-       This cache is currently enabled with SIMPLE_SPEEDUP in typemanager.cs.  Memory consumption
-       went down from 74 megs to 65 megs with this change.  
+****************************************************************************************
+* 
+*   The information on the rest of this file is mostly outdated, and its kept here for
+*   historical reasons
+*
+****************************************************************************************
+ 
+Error Reporting:
+----------------

 
 

-Ideas:
-------
+       * Make yyerror show a nice syntax error, instead of the current mess.

 
 

-       Instead of the hack that *knows* about System.Object not having any children classes,
-       we should just make it simple for a probe to know that there is no need for it.
+Iterators
+---------
+       * Reset should throw not implemented now.

 
 

-The use of DottedName
----------------------
+Optimization ideas
+------------------

 
 

-       We could probably use a different system to represent names, like this:
+       Currently when we build a type cache, it contains private members,
+       internal members, and internal protected members;   We should trim
+       these out, as it shows up on the profile.

 
 

-       class Name {
-               string simplename;
-               Name parent;
-       }
+       We create too many Arraylists;  When we know the size, we should create
+       an array;

 
 

-       So `System.ComponentModel' becomes:
+       During parsing we use arraylists to accumulate data, like this:

 
 

-               x: (System, null)
-               y: (ComponentModel, x)
+               thing:
+               
+               thing_list
+                       : thing { $$ =new ArrayList (); $$.Add ($1); }
+                       | thing_list thing { ArrayList a = $1; a.Add ($2); $$ = a; }

 
 

-       The problem is that we would still need to construct the name to pass to
-       GetType.
+       We probably could start using "Pairs" there:

 
 

-current_container/current_namespace and the DeclSpace
------------------------------------------------------
+               thing_list
+                       : thing { $$ = new Pair ($1, null); }
+                       | thing_list thing { Pair p = $1; $$ = new Pair ($2, $1); }

 
 

-       We are storing fully qualified names in the DeclSpace instead of the node,
-       this is because `current_namespace' (Namepsace) is not a DeclSpace like
-       `current_container'.

 
 

-       The reason for storing the full names today is this:
+EmitContext.ResolveTypeTree
+---------------------------

 
 

-       namespace X {
-               class Y {
-               }
-       }
+       We should investigate its usage.  The problem is that by default
+       this will be set when calling FindType, that triggers a more expensive
+       lookup.

 
 

-       namespace A {
-               class Y {
-               }
-       }
+       I believe we should pass the current EmitContext (which has this turned off
+       by default) to ResolveType/REsolveTypeExpr and then have the routines that
+       need ResolveType to pass null as the emit context.

 
 

-       The problem is that we only use the namespace stack to track the "prefix"
-       for typecontainers, but they are not typecontainers themselves, so we have
-       to use fully qualified names, because both A.X and A.Y would be entered
-       in the toplevel type container.  If we use the short names, there would be
-       a name clash.
+DeclareLocal audit
+------------------

 
 

-       To fix this problem, we have to make namespaces DeclSpaces.
+       DeclareLocal is used in various statements.  The audit should be done
+       in two steps:

 
 

-       The full size, contrasted with the size that could be stored is:
-               corlib:
-                       Size of strings held: 368901
-                       Size of strings short: 147863
+               * Identify all the declare locals.

 
 

-               System:
-                       Size of strings held: 212677
-                       Size of strings short: 97521
-               
-               System.XML:
-                       Size of strings held: 128055
-                       Size of strings short: 35782
-               
-               System.Data:
-                       Size of strings held: 117896
-                       Size of strings short: 36153
-               
-               System.Web:
-                       Size of strings held: 194527
-                       Size of strings short: 58064
-               
-               System.Windows.Forms:
-                       Size of strings held: 220495
-                       Size of strings short: 64923
+               * Identify its uses.

 
 

-       
-TODO:
+               * Find if we can make wrapper functions for all of them.

 
 

-       1. Create a "partial" emit context for each TypeContainer..
+       Then we can move DeclareLocal into a helper class.

 
 

-       2. EmitContext should be partially constructed.  No IL Generator.
+       This is required to fix foreach in iterators.

 
 

-       interface_type review.
+Ideas:
+------

 
 

-       parameter_array, line 952: `note: must be a single dimension array type'.  Validate this
+       Instead of the hack that *knows* about System.Object not having any children classes,
+       we should just make it simple for a probe to know that there is no need for it.

 
 Dead Code Elimination bugs:
 ---------------------------
 
 Dead Code Elimination bugs:
 ---------------------------


@@ -185,30 +129,13 @@ Dead Code Elimination bugs:
 
 Major tasks:
 ------------
 
 Major tasks:
 ------------

-
-       Pinned and volatile require type modifiers that can not be encoded
-       with Reflection.Emit.
-

        Properties and 17.6.3: Finish it.
 
        Properties and 17.6.3: Finish it.
 

-       Implement base indexer access.
-

 readonly variables and ref/out
        
 BUGS
 ----
 
 readonly variables and ref/out
        
 BUGS
 ----
 

-* Check for Final when overriding, if the parent is Final, then we cant
-  allow an override.
-
-* Interface indexers
-
-       I have not figured out why the Microsoft version puts an
-       `instance' attribute, and I am not generating this `instance' attribute.
-
-       Explanation: The reason for the `instance' attribute on
-       indexers is that indexers only apply to instances
-

 * Break/Continue statements
 
        A finally block should reset the InLoop/LoopBegin/LoopEnd, as
 * Break/Continue statements
 
        A finally block should reset the InLoop/LoopBegin/LoopEnd, as


@@ -240,11 +167,6 @@ PENDING TASKS
 
 * Merge test 89 and test-34
 
 
 * Merge test 89 and test-34
 

-* Revisit
-
-       Primary-expression, as it has now been split into 
-       non-array-creation-expression and array-creation-expression.
-               

 * Code cleanup
 
        The information when registering a method in InternalParameters
 * Code cleanup
 
        The information when registering a method in InternalParameters


@@ -254,12 +176,6 @@ PENDING TASKS
 
        Handle modreq from public apis.
 
 
        Handle modreq from public apis.
 

-* Emit `pinned' for pinned local variables.
-
-       Both `modreq' and pinned will require special hacks in the compiler.
-
-* Make sure that we are pinning the right variable
-

 * Merge tree.cs, rootcontext.cs
 
 OPTIMIZATIONS
 * Merge tree.cs, rootcontext.cs
 
 OPTIMIZATIONS


@@ -283,38 +199,11 @@ OPTIMIZATIONS
        The only pending problem is that the code that implements Aliases
        is on TypeContainer, and probably should go in DeclSpace.
 
        The only pending problem is that the code that implements Aliases
        is on TypeContainer, and probably should go in DeclSpace.
 

-* Use of local temporary in UnaryMutator
-
-       We should get rid of the Localtemporary there for some cases
-
-       This turns out to be very complex, at least for the post-version,
-       because this case:
-
-               a = i++
-
-       To produce optimal code, it is necessary for UnaryMutator to know 
-       that it is being assigned to a variable (the way the stack is laid
-       out using dup requires the store to happen inside UnaryMutator).
-
-* Emitcontext
-
-       Do we really need to instanciate this variable all the time?
-
-       It could be static for all we care, and just use it for making
-       sure that there are no recursive invocations on it.
-

 * Tests
 
        Write tests for the various reference conversions.  We have
        test for all the numeric conversions.
 
 * Tests
 
        Write tests for the various reference conversions.  We have
        test for all the numeric conversions.
 

-* Optimizations
-
-       In Indexers and Properties, probably support an EmitWithDup
-       That emits the code to call Get and then leaves a this pointer
-       in the stack, so that later a Store can be emitted using that
-       this pointer (consider Property++ or Indexer++)
-

 * Optimizations: variable allocation.
 
        When local variables of a type are required, we should request
 * Optimizations: variable allocation.
 
        When local variables of a type are required, we should request


@@ -323,12 +212,6 @@ OPTIMIZATIONS
 
 * Add a cache for the various GetArrayMethod operations.
 
 
 * Add a cache for the various GetArrayMethod operations.
 

-* TypeManager.FindMembers:
-
-       Instead of having hundreds of builder_to_blah hash table, have
-       a single one that maps a TypeBuilder `t' to a set of classes
-       that implement an interface that supports FindMembers.
-

 * MakeUnionSet Callers
 
        If the types are the same, there is no need to compute the unionset,
 * MakeUnionSet Callers
 
        If the types are the same, there is no need to compute the unionset,


@@ -359,8 +242,14 @@ RECOMMENDATIONS
        Notice how numbering of the arguments changes as the
        { oob_stack.Push (lexer.Location) } takes a "slot"  in the productions.
 
        Notice how numbering of the arguments changes as the
        { oob_stack.Push (lexer.Location) } takes a "slot"  in the productions.
 

-* local_variable_declaration

 
 

-       Not sure that this grammar is correct, we might have to
-       resolve this during semantic analysis.
+* Anonymous Methods
+===================
+
+In EmitAnonymousHelperClasses we set the "NeedThis" parameter of all
+the roots, but this is not necessary.  We should track the
+"HaveCapturedFields" on a per-ScopeInfo basis, and only set the
+HaveCapturedFields on the proper roots, instead of all the roots.
+
+