TODO

Essential

• SSA is broken by simplify_loads() & branches rewriting/simplification
• add support for bitwise enums (wip)

Documentation

• document the API
• document the limitations of modifying ptrlists during list walking
• document the data structures
• document flow of data / architecture / code structure

Core

• if a variable has its address taken but in an unreachable BB then its MOD_ADDRESSABLE may be wrong and it won't be SSA converted.
  • let kill_insn() check killing of SYMADDR,
  • add the sym into a list and
  • recalculate the addressability before memops's SSA conversion
• bool_ctype should be split into internal 1-bit / external 8-bit

Testsuite

• there are 60 failing tests. They should be fixed (but most are non-trivial to fix).

Misc

• GCC‘s -Wenum-compare / clangs’s -Wenum-conversion -Wassign-enum
• parse _attribute((fallthrough))
• add support for format(printf()) (WIP by Ben Dooks)
• make use of UNDEFs (issues warnings, simplification, ... ?)
• make memory accesses more explicit: add EXPR_ACCESS (wip)
• it would be nice to do our own parsing of floating point (wip)
• some header files needed for crypto/ need __vector or __fp16
• some even need __complex

Optimization

• a lot of small simplifications are waiting to be upstreamed
• the domtree need to be rebuilt (or updated)
• critical edges need to be split
• the current way of doing CSE uses a lot of time
• add SSA based DCE
• add SSA based PRE
• Add SSA based SCCP
• add a pass to inline small functions during simplification.
• use better/more systematic use of internal verification framework
• tracking of operands size should be improved (WIP)
• OP_INLINE is sometimes in the way
• would be nice to strictly separate phases that don't changes the CFG and thus the dominance tree.

IR

---

• pseudos are untyped, it's usually OK but often it complicates things:

  • PSEUDO_REGs are defined by instructions and their type is normally retrievable via this defining instruction but in some cases they're not: for example, pseudos defined by ASM output.
  • PSEUDO_ARGs are considered as defined by OP_ENTRY and are used like this for liveness trackability but their type can't simply be retrieved via this instruction like PSEUDO_REGs are (with ->def->type).
  • PSEUDO_VALs are completely typeless.

  Maybe a few bits should be used to store some kind of low-level type.

• OP_SET should return a bool, always

• add IR instructions for va_arg() & friends

• add a possibility to import of file in “IR assembly”

• dump the symtable

• dump the CFG

LLVM

• fix ...

Internal backends

• it would be nice the upstream the code generator
• add a pass to transform 3-addresses code to 2-addresses
• add some basic register allocation
• add a pass to order the BBs and changes 2-ways CBR into one-way branches
• what can be done for x86?
• add support to add constraints in the MD rules

Longer term/to investigate

• attributes are represented as ctypes‘s alignment, modifiers & contexts but plenty of attributes doesn’t fit, for example they need arguments.

  • format(printf, ...),
  • section(“...”)
  • assume_aligned(alignment[, offsert])
  • error(“message”), warning(“message”)
  • ...

• should support “-Werror=...” ?

• All warning messages should include the option how to disable it. For example:

  “warning: Variable length array is used.”

  should be something like:

  “warning: Variable length array is used. (-Wno-vla)”

• ptrlists must not have elements removed while being iterated; this should somehow be enforced.

• having ‘struct symbol’ used to represent symbols and types is quite handy but it also creates lots of problems and complications

• Possible mixup of symbol for a function designator being not a pointer? This seems to make evaluation of function pointers much more complex than needed.

• extend test-inspect to inspect more AST fields.

• extend test-inspect to inspect instructions.