Replace the isa::Legalize enumeration with a function pointer. This
allows an ISA to define its own specific legalization actions instead of
relying on the default two.
Generate a LEGALIZE_ACTIONS table for each ISA which contains
legalization function pointers indexed by the legalization codes that
are already in the encoding tables. Include this table in
isa/*/enc_tables.rs.
Give the `Encodings` iterator a reference to the action table and change
its `legalize()` method to return a function pointer instead of an
ISA-specific code.
The Result<> returned from TargetIsa::encode() no longer implements
Debug, so eliminate uses of unwrap and expect on that type.
Instead of generating a single `check_instp()` function, create an array
of individual function pointers for checking instruction predicates.
This makes explicit the jump table in the old check_instp() method and
it gives us a way of determining the number of instruction predicates
that exists.
It turns out that most encoding predicates are expressed as recipe
predicates. This means that the encoding tables can be more compact
since we can check the recipe predicate separately from individual
instruction predicates, and the recipe number is already present in the
table.
- Don't combine recipe and encoding-specific predicates when creating an
Encoding. Keep them separate.
- Generate a table of recipe predicates with function pointers. Many of
these are null.
- Check any recipe predicate before accepting a recipe+bits pair.
This has the effect of making almost all instruction predicates
CODE_ALWAYS.
Two new pieces of information are available for all encoding recipes:
- The size in bytes of an encoded instruction, and
- The range of a branch encoded with the recipe, if any.
In the meta language, EncRecipe takes two new constructor arguments. The
size is required for all encodings and branch_range is required for all
recipes used to encode branches.
The tables returned by recipe_names() and recipe_constraints() are now
collected into an EncInfo struct that is available from
TargetIsa::encoding_info(). This is equivalent to the register bank
tables available fro TargetIsa::register_info().
This cleans of the TargetIsa interface and makes it easier to add
encoding-related information.
On ISAs with no instruction predicates, just emit an unimplemented!()
stub for the check_instp() function. It is unlikely that a finished ISA
will not have any instruction predicates.
Every encoding recipe must specify register constraints on input and
output values.
Generate recipe constraint tables along with the other encoding tables.
The intel, arm32, and arm32 targets were only defined in the meta
language previously. Add Rust implementations too.
This is mostly boilerplate, except for the unit tests in the
registers.rs files.
