SMT: Add property and counterexample directive

Rather than generating SMT from a function called check_sat, now find
any function with a $property directive and generate SMT for it, e.g.

$property
function prop_cap_round_trip(cap: bits(128)) -> bool = {
  let cap_rt = capToBits(capBitsToCapability(true, cap));
  cap == cap_rt
}

$property
function prop_base_lteq_top(capbits: bits(128)) -> bool = {
  let c = capBitsToCapability(true, capbits);
  let (base, top) = getCapBounds(c);
  let e = unsigned(c.E);
  e >= 51 | base <= top
}

The file property.ml has a function for gathering all the properties
in a file, as well as a rewrite-pass for properties with type
quantifiers, which allows us to handle properties like

function prop forall 'n, 'n <= 100. (bv: bits('n)) -> bool = exp

by rewriting to (conceptually)

function prop(bv: bits(MAX_BIT_WIDTH)) -> bool =
  if length(bv) > 100 then true else exp

The function return is now automatically negated (i.e. always true =
unsat, sometimes false = sat), which makes sense for quickcheck-type
properties.

1 files changed, 3 insertions, 2 deletions

diff --git a/test/smt/shiftr_zero_1.sat.sail b/test/smt/shiftr_zero_1.sat.sail
index 9eb75c69..04dd74c4 100644
--- a/test/smt/shiftr_zero_1.sat.sail
+++ b/test/smt/shiftr_zero_1.sat.sail
@@ -4,7 +4,8 @@ $include <prelude.sail>
 
 register R : bits(64)
 
-function check_sat((): unit) -> bool = {
+$property
+function prop((): unit) -> bool = {
   let x = sail_shiftright(R, 63);
-  not_bool(x == 0x0000_0000_0000_0000)
+  x == 0x0000_0000_0000_0000
 }
\ No newline at end of file