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Verify restrictions on polymorphism.

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Add a typevar_operand argument to the InstructionFormat constructor which
determines the operand used for inferring the controlling type variable.

Identify polymorphic instructions when they are created, determine if the
controlling type variable can be inferred from the typevar_operand, and verify
the use of type variables in the other operands.

Generate type variable summary in the documentation, including how the
controlling type variable is inferred.
This commit is contained in:
Jakob Stoklund Olesen
2016-05-19 11:21:36 -07:00
parent 210139c4bd
commit 1e631fdbd6
4 changed files with 187 additions and 19 deletions
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11
docs/metaref.rst
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@@ -145,7 +145,7 @@ representation depends on the input operand kinds and whether the instruction
can produce multiple results.
.. autoclass:: OperandKind
.. inheritance-diagram:: OperandKind ImmediateKind EntityRefkind
.. inheritance-diagram:: OperandKind ImmediateKind EntityRefKind
Since all SSA value operands are represented as a `Value` in Rust code, value
types don't affect the representation. Two special operand kinds are used to
@@ -174,8 +174,13 @@ constraints, in practice more freedom than what is needed for normal instruction
set architectures. In order to simplify the Rust representation of value type
constraints, some restrictions are imposed on the use of type variables.
A polymorphic instruction has a single *controlling type variable*. The value
types of instruction results must be one of the following:
A polymorphic instruction has a single *controlling type variable*. For a given
opcode, this type variable must be the type of the first result or the type of
the input value operand designated by the `typevar_operand` argument to the
:py:class:`InstructionFormat` constructor. By default, this is the first value
operand, which works most of the time.
The value types of instruction results must be one of the following:
1. A concrete value type.
2. The controlling type variable.