| paul@472 | 1 | Name usage types: as parameters, as base classes, as callables. This potentially restricts
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| paul@472 | 2 | attribute usage effects because names mentioned as base classes are not propagated and
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| paul@472 | 3 | made freely available for use in attribute accesses.
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| paul@472 | 4 |
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| paul@419 | 5 | Low-Level Instructions and Macro Instructions
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| paul@419 | 6 | =============================================
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| paul@419 | 7 |
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| paul@429 | 8 | Have contexts and values stored separately in memory. This involves eliminating DataValue
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| paul@429 | 9 | and storing attributes using two words.
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| paul@429 | 10 |
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| paul@419 | 11 | Migrate macro instructions such as the *Index instructions to library code implemented
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| paul@419 | 12 | using low-level instructions.
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| paul@419 | 13 |
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| paul@419 | 14 | Consider introducing classic machine level instructions (word addition, subtraction, and
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| paul@419 | 15 | so on) in order to implement all current RSVP instructions.
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| paul@419 | 16 |
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| paul@450 | 17 | Move common code sequences to a library routine, such as the context checking that occurs
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| paul@450 | 18 | in functions and methods.
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| paul@450 | 19 |
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| paul@464 | 20 | Dataflow Optimisations
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| paul@464 | 21 | ======================
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| paul@450 | 22 |
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| paul@464 | 23 | Assignments, particularly now that no result register exists, may cause StoreTemp/LoadTemp
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| paul@464 | 24 | instruction pairs to be produced and these could be eliminated.
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| paul@450 | 25 |
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| paul@631 | 26 | Ambiguous/Multiple Class/Function Definitions
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| paul@631 | 27 | =============================================
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| paul@631 | 28 |
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| paul@631 | 29 | Classes and functions are not supposed to have multiple definitions, where one code path
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| paul@631 | 30 | may define one form of a class or function with a given name and another code path may
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| paul@631 | 31 | define another form with that name. Currently, such multiple definitions are treated like
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| paul@631 | 32 | "unions" in the object table.
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| paul@631 | 33 |
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| paul@635 | 34 | Consider functions as well as classes which are supported using "shadow" names for the
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| paul@635 | 35 | second and subsequent definitions of classes in the same namespace.
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| paul@635 | 36 |
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| paul@417 | 37 | Class and Module Attribute Assignment
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| paul@417 | 38 | =====================================
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| paul@417 | 39 |
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| paul@557 | 40 | Allow unrestricted class and module assignment (but not new external binding of
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| paul@557 | 41 | attributes), eliminating run-time checks on object types in instructions like
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| paul@557 | 42 | StoreAttrIndex. This may involve less specific objects being identified during inspection.
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| paul@557 | 43 |
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| paul@568 | 44 | Potentially re-evaluate class bases in order to see if they are non-constant.
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| paul@568 | 45 |
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| paul@417 | 46 | Verify that the context information is correctly set, particularly for the unoptimised
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| paul@417 | 47 | cases.
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| paul@417 | 48 |
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| paul@417 | 49 | Update docs/assignment.txt.
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| paul@417 | 50 |
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| paul@431 | 51 | Prevent assignments within classes, such as method aliasing, from causing the source of an
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| paul@431 | 52 | assignment from being automatically generated. Instead, only external references should be
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| paul@431 | 53 | registered.
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| paul@431 | 54 |
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| paul@431 | 55 | Prevent "from <module> import ..." statements from registering references to such local
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| paul@431 | 56 | aliases such that they cause the source of each alias to be automatically generated.
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| paul@431 | 57 |
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| paul@419 | 58 | Consider attribute assignment observations, along with the possibility of class and module
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| paul@419 | 59 | attribute assignment.
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| paul@419 | 60 |
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| paul@419 | 61 | (Note direct assignments as usual, indirect assignments via the attribute usage
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| paul@419 | 62 | mechanism. During attribute collection and inference, add assigned values to all
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| paul@419 | 63 | inferred targets.)
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| paul@419 | 64 |
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| paul@419 | 65 | (Since class attributes can be assigned, StoreAttrIndex would no longer need to reject
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| paul@419 | 66 | static attributes, although this might still be necessary where attribute usage analysis
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| paul@419 | 67 | has not been performed.)
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| paul@419 | 68 |
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| paul@419 | 69 | Potentially consider changing static attribute details to use object-relative offsets in
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| paul@419 | 70 | order to simplify the instruction implementations. This might allow us to eliminate the
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| paul@419 | 71 | static attribute flag for attributes in the object table, at least at run-time.
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| paul@419 | 72 |
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| paul@413 | 73 | Dynamic Attribute Access
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| paul@413 | 74 | ========================
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| paul@413 | 75 |
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| paul@425 | 76 | Consider explicit accessor initialisation:
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| paul@425 | 77 |
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| paul@425 | 78 | attr = accessor("attr")
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| paul@425 | 79 | getattr(C, attr)
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| paul@413 | 80 |
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| paul@394 | 81 | Attribute Usage
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| paul@394 | 82 | ===============
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| paul@394 | 83 |
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| paul@498 | 84 | To consider: is it useful to distinguish between attribute name sets when the same names
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| paul@498 | 85 | are mentioned, but where one path through the code sets different values on attributes
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| paul@498 | 86 | than another? The _attrtypes collapses observations in order to make a list of object
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| paul@498 | 87 | types for a name, and the final set of names leading to such type deductions might be a
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| paul@498 | 88 | useful annotation to be added alongside _attrcombined.
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| paul@498 | 89 |
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| paul@613 | 90 | (Update the reports to group identical sets of attribute names.)
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| paul@613 | 91 |
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| paul@613 | 92 | Attribute usage on attributes might be possible if one can show that the expression of an
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| paul@613 | 93 | attribute access is constant and that the attribute target is also constant or only refers
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| paul@613 | 94 | to a single type. For example, in the sys module:
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| paul@613 | 95 |
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| paul@613 | 96 | stderr = file()
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| paul@613 | 97 |
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| paul@613 | 98 | If no work is done to associate the result of the invocation with the stderr name, then
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| paul@613 | 99 | one could instead at least attempt to determine whether stderr is assigned only once. If
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| paul@613 | 100 | so, it might be possible to record attribute usage on references to the name. For example:
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| paul@613 | 101 |
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| paul@613 | 102 | sys.stderr.write(...) # sys.stderr supports write -> {file, ...}
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| paul@575 | 103 |
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| paul@498 | 104 | Interface/Type Generalisation
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| paul@498 | 105 | -----------------------------
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| paul@498 | 106 |
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| paul@480 | 107 | Consolidate interface observations by taking all cached table accesses and determining
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| paul@480 | 108 | which usage patterns lead to the same types. For example, if full usage of {a, b} and
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| paul@480 | 109 | {a, b, c} leads to A and B in both cases, either {a, b} can be considered as partial usage
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| paul@480 | 110 | of the complete interface {a, b, c}, or the latter can be considered as an
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| paul@480 | 111 | overspecification of the former.
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| paul@480 | 112 |
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| paul@364 | 113 | Consider type deduction and its consequences where types belong to the same hierarchy
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| paul@364 | 114 | and where a guard could be generated for the most general type.
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| paul@364 | 115 |
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| paul@364 | 116 | Consider permitting multiple class alternatives where the attributes are all identical.
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| paul@364 | 117 |
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| paul@360 | 118 | Support class attribute positioning similar to instance attribute positioning, potentially
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| paul@360 | 119 | (for both) based on usage observations. For example, if __iter__ is used on two classes,
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| paul@360 | 120 | the class attribute could be exposed at a similar relative position to the class (and
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| paul@360 | 121 | potentially accessible using a LoadAttr-style instruction).
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| paul@360 | 122 |
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| paul@394 | 123 | **** Constant attribute users need not maintain usage since they are already resolved. ****
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| paul@394 | 124 |
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| paul@613 | 125 | Self-Related Usage
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| paul@498 | 126 | ------------------
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| paul@498 | 127 |
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| paul@498 | 128 | Perform attribute usage on attributes of self as names, potentially combining observations
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| paul@498 | 129 | across methods.
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| paul@498 | 130 |
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| paul@498 | 131 | Additional Guards
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| paul@498 | 132 | -----------------
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| paul@498 | 133 |
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| paul@710 | 134 | Consider handling branches of values within namespaces in order to support more precise
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| paul@710 | 135 | value usage.
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| paul@498 | 136 |
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| paul@498 | 137 | Loop entry points and other places where usage becomes more specific might be used as
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| paul@498 | 138 | places to impose guards. See tests/attribute_access_type_restriction_loop_list.py for an
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| paul@498 | 139 | example. (Such information is already shown in the reports.)
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| paul@498 | 140 |
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| paul@498 | 141 | Strict Interfaces/Types
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| paul@498 | 142 | -----------------------
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| paul@498 | 143 |
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| paul@498 | 144 | Make the gathering of usage parameterisable according to the optimisation level so that a
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| paul@498 | 145 | choice can be made between control-flow-dependent observations and the simple collection
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| paul@498 | 146 | of all attributes used with a name (producing a more static interface observation).
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| paul@498 | 147 |
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| paul@498 | 148 | AttributeError
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| paul@498 | 149 | --------------
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| paul@498 | 150 |
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| paul@504 | 151 | Consider attribute usage observations being suspended or optional inside blocks where
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| paul@504 | 152 | AttributeError may be caught (although this doesn't anticipate such exceptions being
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| paul@504 | 153 | caught outside a function altogether). For example:
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| paul@504 | 154 |
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| paul@504 | 155 | y = a.y
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| paul@504 | 156 | try:
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| paul@504 | 157 | z = a.z # z is an optional attribute
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| paul@504 | 158 | except AttributeError:
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| paul@504 | 159 | z = None
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| paul@498 | 160 |
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| paul@394 | 161 | Frame Optimisations
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| paul@394 | 162 | ===================
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| paul@394 | 163 |
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| paul@394 | 164 | Stack frame replacement where a local frame is unused after a call, such as in a tail call
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| paul@394 | 165 | situation.
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| paul@394 | 166 |
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| paul@394 | 167 | Local assignment detection plus frame re-use. Example: slice.__init__ calls
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| paul@394 | 168 | xrange.__init__ with the same arguments which are unchanged in xrange.__init__. There is
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| paul@419 | 169 | therefore no need to build a new frame for this call, although in some cases the locals
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| paul@419 | 170 | frame might need expanding.
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| paul@419 | 171 |
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| paul@456 | 172 | Reference tracking where objects associated with names are assigned to attributes of other
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| paul@456 | 173 | objects may assist in allocation optimisations. Recording whether an object referenced by
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| paul@456 | 174 | a name is assigned to an attribute, propagated to another name and assigned to an
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| paul@456 | 175 | attribute, or passed to another function or method might, if such observations were
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| paul@456 | 176 | combined, allow frame-based or temporary allocation to occur.
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| paul@456 | 177 |
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| paul@620 | 178 | Instantiation Deduction
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| paul@620 | 179 | =======================
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| paul@620 | 180 |
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| paul@620 | 181 | Consider handling Const, List and Tuple in micropython.inspect in order to produce
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| paul@620 | 182 | instances of specific classes. Then, consider adding support for guard
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| paul@620 | 183 | removal/verification where known instances are involved. For example:
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| paul@620 | 184 |
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| paul@620 | 185 | l = []
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| paul@620 | 186 | l.append(123) # type deductions are filtered using instantiation knowledge
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| paul@620 | 187 |
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| paul@620 | 188 | Currently, this is done only for Const values in the context of attribute accesses during
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| paul@620 | 189 | inspection.
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| paul@620 | 190 |
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| paul@710 | 191 | Handling CallFunc in a similar way is more challenging. Consider the definitions in the
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| paul@710 | 192 | sys module:
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| paul@472 | 193 |
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| paul@620 | 194 | stderr = file()
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| paul@620 | 195 |
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| paul@620 | 196 | It must first be established that file only ever refers to the built-in file class, and
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| paul@620 | 197 | only then can the assumption be made that stderr in this case refers to instances of file.
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| paul@620 | 198 | If file can also refer to other objects, potential filtering operations are more severely
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| paul@620 | 199 | limited.
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| paul@620 | 200 |
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| paul@710 | 201 | Propagation of type information can also occur. For example:
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| paul@710 | 202 |
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| paul@710 | 203 | DeducedSource(module, program).deduce()
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| paul@710 | 204 |
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| paul@710 | 205 | The DeducedSource invocation, if yielding an instance of the DeducedSource class, can then
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| paul@710 | 206 | supply the attribute access operation with type information.
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| paul@710 | 207 |
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| paul@710 | 208 | A more advanced example involves accesses then invocations:
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| paul@710 | 209 |
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| paul@710 | 210 | x = self.__class__()
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| paul@710 | 211 |
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| paul@710 | 212 | Here, the effect should be the inference that x may refer to an instance of one of a
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| paul@710 | 213 | number of eligible types of which self is also an instance.
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| paul@710 | 214 |
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| paul@620 | 215 | Invocation-Related Deduction
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| paul@620 | 216 | ============================
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| paul@620 | 217 |
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| paul@620 | 218 | Where an attribute access (either in conjunction with usage observations or independently)
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| paul@620 | 219 | could refer to a number of different targets, but where the resulting attribute is then
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| paul@620 | 220 | used in an invocation, filtering of the targets could be done to eliminate any targets
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| paul@620 | 221 | that are not callable. Guards would need introducing to prevent inappropriate operations
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| paul@620 | 222 | from occurring at run-time.
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| paul@472 | 223 |
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| paul@419 | 224 | Inlining
|
| paul@419 | 225 | ========
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| paul@419 | 226 |
|
| paul@419 | 227 | Where a function or method call can always be determined, the body of the target could be
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| paul@419 | 228 | inlined - copied into place - within the caller. If the target is only ever called by a
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| paul@456 | 229 | single caller it could be moved into place. This could enhance deductions based on
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| paul@456 | 230 | attribute usage since observations from the inlined function would be merged into the
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| paul@456 | 231 | caller.
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| paul@394 | 232 |
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| paul@672 | 233 | Distinguish between frame sharing and inlining: where a called function does not rebind
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| paul@672 | 234 | its names, and where the frame of the caller is compatible, the frame of the caller might
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| paul@672 | 235 | be shared with the called function even if a branch and return is still involved.
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| paul@672 | 236 |
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| paul@672 | 237 | Suitable candidates for inlining, frame sharing or enhanced analysis might be lambdas and
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| paul@672 | 238 | functions containing a single statement.
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| paul@672 | 239 |
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| paul@394 | 240 | Function Specialisation
|
| paul@394 | 241 | =======================
|
| paul@394 | 242 |
|
| paul@394 | 243 | Specialisation of certain functions, such as isinstance(x, cls) where cls is a known
|
| paul@394 | 244 | constant.
|
| paul@394 | 245 |
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| paul@394 | 246 | Structure and Object Table Optimisations
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| paul@394 | 247 | ========================================
|
| paul@394 | 248 |
|
| paul@394 | 249 | Fix object table entries for attributes not provided by any known object, or provide an
|
| paul@394 | 250 | error, potentially overridden by options. For example, the augmented assignment methods
|
| paul@394 | 251 | are not supported by the built-in objects and thus the operator module functions cause
|
| paul@394 | 252 | the compilation to fail. Alternatively, just supply the methods since something has to do
|
| paul@394 | 253 | so in the builtins.
|
| paul@394 | 254 |
|
| paul@394 | 255 | Consider attribute merging where many attributes are just aliases for the same underlying
|
| paul@394 | 256 | definition.
|
| paul@394 | 257 |
|
| paul@349 | 258 | Consider references to defaults as occurring only within the context of a particular
|
| paul@349 | 259 | function, thus eliminating default value classes if such functions are not themselves
|
| paul@349 | 260 | invoked.
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| paul@349 | 261 |
|
| paul@394 | 262 | Scope Handling
|
| paul@394 | 263 | ==============
|
| paul@394 | 264 |
|
| paul@394 | 265 | Consider merging the InspectedModule.store tests with the scope conflict handling.
|
| paul@394 | 266 |
|
| paul@343 | 267 | Consider labelling _scope on assignments and dealing with the assignment of removed
|
| paul@343 | 268 | attributes, possibly removing the entire assignment, and distinguishing between such cases
|
| paul@343 | 269 | and unknown names.
|
| paul@343 | 270 |
|
| paul@342 | 271 | Check name origin where multiple branches could yield multiple scope interpretations:
|
| paul@342 | 272 |
|
| paul@504 | 273 | try:
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| paul@504 | 274 | set # built-in name
|
| paul@504 | 275 | except NameError:
|
| paul@504 | 276 | from sets import Set as set # local definition of name
|
| paul@342 | 277 |
|
| paul@504 | 278 | set # could be confused by the local definition at run-time
|
| paul@342 | 279 |
|
| paul@394 | 280 | Object Coverage
|
| paul@394 | 281 | ===============
|
| paul@394 | 282 |
|
| paul@332 | 283 | Support __init__ traversal (and other implicit names) more effectively.
|
| paul@332 | 284 |
|
| paul@499 | 285 | Importing Modules
|
| paul@499 | 286 | =================
|
| paul@499 | 287 |
|
| paul@710 | 288 | (Explicit relative imports are now supported.) Consider supporting relative imports, even
|
| paul@710 | 289 | though this is arguably a misfeature.
|
| paul@499 | 290 |
|
| paul@394 | 291 | Other
|
| paul@394 | 292 | =====
|
| paul@394 | 293 |
|
| paul@332 | 294 | Check context_value initialisation (avoiding or handling None effectively).
|
| paul@332 | 295 |
|
| paul@342 | 296 | Consider better "macro" support where new expressions need to be generated and processed.
|
| paul@402 | 297 |
|
| paul@402 | 298 | Detect TestIdentity results involving constants, potentially optimising status-affected
|
| paul@402 | 299 | instructions:
|
| paul@402 | 300 |
|
| paul@402 | 301 | TestIdentity(x, y) # where x is always y
|
| paul@402 | 302 | JumpIfFalse(...) # would be removed (never false)
|
| paul@402 | 303 | JumpIfTrue(...) # changed to Jump(...)
|
| paul@402 | 304 |
|
| paul@402 | 305 | Status-affected blocks could be optimised away for such constant-related results.
|
| paul@672 | 306 |
|
| paul@672 | 307 | Caching of structure and attribute usage information for incremental compilation.
|
