C backend improvements

- Propagate types more accurately to improve optimization on ANF
  representation.

- Add a generic optimization pass to remove redundant variables that
  simply alias other variables.

- Modify Sail interactive mode, so it can compile a specification with
  the :compile command, view generated intermediate representation via
  the :ir <function> command, and step-through the IR with :exec <exp>
  (although this is very incomplete)

- Introduce a third bitvector representation, between fast
  fixed-precision bitvectors, and variable length large
  bitvectors. The bitvector types are now from most efficient to least

   * CT_fbits for fixed precision, 64-bit or less bitvectors
   * CT_sbits for 64-bit or less, variable length bitvectors
   * CT_lbits for arbitrary variable length bitvectors

- Support for generating C code using CT_sbits is currently
  incomplete, it just exists in the intermediate representation right
  now.

- Include ctyp in AV_C_fragment, so we don't have to recompute it

1 files changed, 1 insertions, 0 deletions

diff --git a/src/constant_fold.ml b/src/constant_fold.ml
index 407bd69a..f22b48de 100644
--- a/src/constant_fold.ml
+++ b/src/constant_fold.ml
@@ -100,6 +100,7 @@ let safe_primops =
       "prerr_string";
       "read_ram";
       "write_ram";
+      "get_time_ns";
       "Elf_loader.elf_entry";
       "Elf_loader.elf_tohost"
     ]