Cretonne IL frontend: ILBuilder (#97)

* API and data structures proposal for the SSA construction module

* Polished API and implemented trivial functions

* API more explicit, Variable now struct parameter

* Sample test written to see how the API could be used

* Implemented local value numbering for SSABuilder

* Implemented SSA within a single Ebb

* Unfinished unoptimized implementation for recursive use and seal

* Working global value numbering
The SSABuilder now create ebb args and modifies jump instructions accordingly

* Updated doc and improved branch argument modifying.
Removed instructions::branch_arguments and instructions::branch_argument_mut

* SSA building: bugfix, asserts and new test case
Missing a key optimization to remove cycles of Phi

* SSA Building: small changes after code review
Created helper function for seal_block (which now contains sanity checks)

* Optimization: removed useless phis (ebb arguments)
Using pessimistic assumption that when using a non-def variable in an unsealed block we create an ebb argument which is removed when sealing if we detect it as useless
Using aliases to avoid rewriting variables

* Changed the semantics of remove_ebb_arg and turned it into a proper API method

* Adapted ssa branch to changes in the DFG API

* Abandonned SparseMaps for EntityMaps, added named structure for headr block data.

* Created skeletton for a Cretonne IL builder frontend

* Frontend IL builder: first draft of implementation with example of instruction methods

* Working basic implementation of the frontend
Missing handling of function arguments and return values

* Interaction with function signature, sample test, more checks

* Test with function verifier, seal and fill sanity check

* Implemented python script to generate ILBuilder methods

* Added support for jump tables and stack slot

* Major API overhaul
* No longer generating rust through Python but implements InstBuilder
* No longer parametrized by user's blocks but use regular `Ebb`
* Reuse of allocated memory via distinction between ILBuilder and FunctionBuilder

* Integrate changes from StackSlot

* Improved error message

* Added support for jump arguments supplied by the user

* Added an ebb_args proxy method needed

* Adapted to Entity_ref splitted into a new module

* Better error messages and fixed tests

* Added method to change jump destination

* We whould be able to add unreachable code

* Added inst_result proxy to frontend

* Import support

* Added optimization for SSA construction:
If multiple predecessors but agree on value don't create EBB argument

* Move unsafe and not write-only funcs apart, improved doc

* Added proxy function for append_ebb_arg

* Support for unreachable code and better layout of the Ebbs

* Fixed a bug yielding an infinite loop in SSA construction

* SSA predecessors lookup code refactoring

* Fixed bug in unreachable definition

* New sanity check and display debug function

* Fixed bug in verifier and added is_pristine ;ethod for frontend

* Extended set of characters printable in function names
To be able to print names of functions in test suite

* Fixes and improvements of SSA construction after code review

* Bugfixes for frontend code simplification

* On-the-fly critical edge splitting in case of br_table with jump arguments

* No more dangling undefined values, now attached as EBB args

* Bugfix: only split corresponding edges on demand, not all br_table edges

* Added signature retrieval method

* Bugfix for critical edge splitting not sealing the ebbs it created

* Proper handling of SSA side effects by the frontend

* Code refactoring: moving frontend and SSA to new crate

* Frontend: small changes and bugfixes after code review

Cargo.toml

@@ -15,6 +15,7 @@ path = "src/cton-util.rs"
 [dependencies]
 cretonne = { path = "lib/cretonne" }
 cretonne-reader = { path = "lib/reader" }
+cretonne-frontend = { path ="lib/frontend" }
 filecheck = { path = "lib/filecheck" }
 docopt = "0.8.0"
 serde = "1.0.8"