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Use generated exprs to test expression evaluation against smt solver #499

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@ailrst ailrst commented Jul 9, 2025 •
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Reuses the scalacheck-based expr generator to test the interpreter against z3 with more complex expressions:

- interp exprs smt
  + [INFO]   assert: neq(sign_extend(62, bvcomp(bvand(bvudiv(bvnot(0x0:bv63), 0x1:bv63), 0x7fffffffffffffff:bv63), 0x0:bv63)), 0x0:bv63) 
  + [INFO]   assert: neq(bvnand(0x15e32bf08bbb32fbcf:bv70, 0x1a00f75631050b732d:bv70), 0x2fffdcaffefefd8cf2:bv70) 
  + [INFO]   assert: neq(bvnot(0x19b5ae9950e0e6cf316dc7b480b9ea8f:bv128), 0xe64a5166af1f1930ce92384b7f461570:bv128) 
  + [INFO]   assert: neq(zero_extend(62, booltobv1(bvule(0x1:bv63, 0x0:bv63))), 0x0:bv63) 
  + [INFO]   assert: neq(bvsmod(bvneg(0x1:bv31), 0x7fffffff:bv31), 0x0:bv31) 
  + [INFO]   assert: neq(bvnot(0x1:bv33), 0x1fffffffe:bv33) 
  + [INFO]   assert: neq(bvnot(0x1:bv70), 0x3ffffffffffffffffe:bv70) 
  + [INFO]   assert: neq(bvnot(0x0:bv60), 0xfffffffffffffff:bv60) 
  + [INFO]   assert: neq(bvneg(0x1:bv70), 0x3fffffffffffffffff:bv70) 
  + [INFO]   assert: neq(zero_extend(30, booltobv1(bvsle(0x69b19af1:bv31, bvnot(0x1f793f2e:bv31)))), 0x0:bv31) 
  + [INFO]   assert: neq(bvshl(sign_extend(89, booltobv1(bvuge(0x3ffffffffffffffffffffff:bv90, 0x2f68ea76c42885ff0c88b73:bv90))), 0x36:bv90), 0x3ffffffffc0000000000000:bv90) 
  + [INFO]   assert: neq(zero_extend(30, booltobv1(bvuge(sign_extend(30, booltobv1(bvuge(0x1e5c3fde:bv31, 0x2db1d16d:bv31))), 0x3677dc24:bv31))), 0x0:bv31) 
  + [INFO]   assert: neq(zero_extend(32, booltobv1(bvule(bvudiv(bvneg(0x0:bv33), 0x1:bv33), bvneg(0x1ffffffff:bv33)))), 0x1:bv33) 
  + [INFO]   assert: neq(bvnot(0x3766a351d19a7bc29005d934c8fcd504:bv126), 0x8995cae2e65843d6ffa26cb37032afb:bv126) 
  + [INFO]   assert: neq(zero_extend(31, bvcomp(0xffffffff:bv32, bvnor(bvneg(0x1:bv32), 0x99c9e959:bv32))), 0x0:bv32) 
  + [INFO]   assert: neq(bvneg(0x1b28bc4a:bv31), 0x64d743b6:bv31) 
  + [INFO]   assert: neq(bvneg(0x0:bv32), 0x0:bv32) 
  + [INFO]   assert: neq(sign_extend(59, booltobv1(bvult(0xfb24180c63f4525:bv60, 0xfffffffffffffff:bv60))), 0xfffffffffffffff:bv60) 
  + [INFO]   assert: neq(bvneg(0x0:bv33), 0x0:bv33) 
  + [INFO]   assert: neq(bvnot(0x0:bv128), 0xffffffffffffffffffffffffffffffff:bv128) 
  + [INFO]   assert: neq(bvlshr(sign_extend(59, booltobv1(bvsge(bvnot(0x880b8e6f8e11f8:bv60), bvlshr(0x25aa40786bf3cdc:bv60, 0x1:bv60)))), 0xd6:bv60), 0x0:bv60) 
  + [INFO]   assert: neq(bvsdiv(bvneg(0x2899bb9d09f3db10bafec32:bv90), 0x3ffffffffffffffffffffff:bv90), 0x2899bb9d09f3db10bafec32:bv90) 
  + [INFO]   assert: neq(bvneg(0x395dda0f03f38d333:bv66), 0x6a225f0fc0c72ccd:bv66) 
  + [INFO]   assert: neq(bvxor(bvnot(0x0:bv65), bvnot(0xfa98ca06c1f394b1:bv65)), 0xfa98ca06c1f394b1:bv65) 
  + [INFO]   assert: neq(bvneg(0x0:bv64), 0x0:bv64) 
  + [INFO]   assert: neq(bvneg(0xfc564e010da8d8de2bcafc0be1cd2ca2:bv128), 0x3a9b1fef2572721d43503f41e32d35e:bv128) 
  + [INFO]   assert: neq(sign_extend(31, booltobv1(bvult(bvnot(0x0:bv32), bvashr(0xb7fc0d74:bv32, 0x1:bv32)))), 0x0:bv32) 
  + [INFO]   assert: neq(sign_extend(125, booltobv1(bvult(0x1c1420a28cbe4d2ff5fe8c84371b8c78:bv126, bvneg(0x3efb140cc8e88070a548614899a189b6:bv126)))), 0x0:bv126) 
  + [INFO]   assert: neq(bvxnor(sign_extend(63, bvcomp(bvnand(0xffffffffffffffff:bv64, bvneg(0x0:bv64)), 0x3b6c08abd2135a4e:bv64)), bvor(0xb694a734c9dc99bd:bv64, bvnot(0x97e2c00a92ef616e:bv64))), 0x162400a12236042:bv64) 
  + [INFO]   assert: neq(bvneg(0x28ade1bb:bv30), 0x17521e45:bv30)

@b-paul

This test tends to time out when it generates difficult expressions, maybe z3's simplify tactic would be more appropriate than just an assertion.

katrinafyi
katrinafyi approved these changes Jul 22, 2025
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src/main/scala/util/z3/z3process.scala
Comment on lines +12 to +19
val t = timeoutSec match {
case Some(n) => Seq(s"-T:$n")
case _ => Seq()
}
val softT = softTimeoutMillis match {
case Some(n) => Seq(s"-t:$n")
case None => Seq()
}
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@katrinafyi katrinafyi Jul 22, 2025

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use .map. Options can be ++-ed onto a sequence and they act like a sequence of zero or one items.

src/test/scala/ExprGen.scala
Comment on lines +97 to +102
def genExpr(size: Option[Int] = None, depthLimit: Int = 10): Gen[Expr] =
if (size.exists(_ <= 1) || depthLimit <= 0) then genValue(size)
else Gen.oneOf(genBinExp(size, depthLimit - 1), genUnExp(size), genValue(size))

def genNonLiteralExpr(size: Option[Int] = None, depthLimit: Int = 3): Gen[Expr] =
if (size.exists(_ <= 1)) then genValue(size) else Gen.oneOf(genBinExp(size, depthLimit), genUnExp(size))
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ik it's not new in this pr, but what is this condition on size.exists(_ <= 1)? so, if size is negative or 0, it'll get passed to genValue? this seems wrong

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@ailrst ailrst Jul 22, 2025

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Its ugly but its because you can reliably generate width 1 bitvectors but the other options need more careful consideration as they sometimes try and partition it down further, e.g. bvconcat. I just didnt bother dealing with each possible leaf needed for the other cases. note size is option

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ailrst commented Jul 29, 2025

I don't think theres a way to reliably generate expressions that its possible for Z3 to always verify within a timeframe, maybe I just let timeouts silently pass the test (maybe there's a way to ask scalacheck to generate more checks in that case to make sure there's a certain number of positive examples?). I don't think we should merge as is since it will lead to unreliable failures from timeouts.

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agle commented Aug 25, 2025

@katrinafyi I guess we can just mark this as disabled and merge so we can run manually? Its a somewhat useful test to have but probably too flaky.

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katrinafyi commented Aug 25, 2025

That makes sense. Should the scalacheck cases be in a different test suite so that the existing genSMT can still run?

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agle commented Aug 25, 2025

Yeah

@agle agle self-assigned this Aug 25, 2025
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