This PR establishes `String.ofList` and `String.toList` as the preferred
method for converting between strings and lists of characters and
deprecates the alternatives `String.mk`, `List.asString` and
`String.data`.
This PR adds support the Count Trailing Zeros operation `BitVec.ctz` to
the bitvector library and to `bv_decide`, relying on the existing `clz`
circuit. We also build some theory around `BitVec.ctz` (analogous to the
theory existing for `BitVec.clz`) and introduce lemmas
`BitVec.[ctz_eq_reverse_clz, clz_eq_reverse_ctz, ctz_lt_iff_ne_zero,
getLsbD_false_of_lt_ctz, getLsbD_true_ctz_of_ne_zero,
two_pow_ctz_le_toNat_of_ne_zero, reverse_reverse_eq,
reverse_eq_zero_iff]`.
`ctz` operation is common in numerous compiler intrinsics (see
[here](https://clang.llvm.org/docs/LanguageExtensions.html#intrinsics-support-within-constant-expressions))
and architectures (see
[here](https://en.wikipedia.org/wiki/Find_first_set)).
---------
Co-authored-by: Siddharth <siddu.druid@gmail.com>
This PR resolves a defeq diamond, which caused a problem in Mathlib:
```
import Mathlib
example (R : Type) [I : Ring R] :
@AddCommGroup.toGrindIntModule R (@Ring.toAddCommGroup R I) =
@Lean.Grind.Ring.instIntModule R (@Ring.toGrindRing R I) := rfl -- fails
```
This PR adjusts the experimental module system to make `private` the
default visibility modifier in `module`s, introducing `public` as a new
modifier instead. `public section` can be used to revert the default for
an entire section, though this is more intended to ease gradual adoption
of the new semantics such as in `Init` (and soon `Std`) where they
should be replaced by a future decl-by-decl re-review of visibilities.
This PR both adds initial `@[grind]` annotations for `BitVec`, and uses
`grind` to remove many proofs from `BitVec/Lemmas`.
---------
Co-authored-by: Sebastian Ullrich <sebasti@nullri.ch>
This PR adds a new `BitVec.clz` operation and a corresponding `clz`
circuit to `bv_decide`, allowing to bitblast the count leading zeroes
operation. The AIG circuit is linear in the number of bits of the
original expression, making the bitblasting convenient wrt. rewriting.
`clz` is common in numerous compiler intrinsics (see
[here](https://clang.llvm.org/docs/LanguageExtensions.html#intrinsics-support-within-constant-expressions))
and architectures (see
[here](https://en.wikipedia.org/wiki/Find_first_set)).
Co-authored by @bollu.
---------
Co-authored-by: Tobias Grosser <github@grosser.es>
Co-authored-by: Siddharth <siddu.druid@gmail.com>
This PR avoids importing all of `BitVec.Lemmas` and `BitVec.BitBlast`
into `UInt.Lemmas`. (They are still imported into `SInt.Lemmas`; this
seems much harder to avoid.)
This PR renames `BitVec.getLsb'` to `BitVec.getLsb`, now that older
deprecated definition occupying that name has been removed. (Similarly
for `BitVec.getMsb'`.)
This PR adds the `@[expose]` attribute to many functions (and changes
some theorems to be by `:= (rfl)`) in preparation for the `@[defeq]`
attribute change in #8419.
This PR adds the instances `Grind.CommRing (Fin n)` and `Grind.IsCharP
(Fin n) n`. New tests:
```lean
example (x y z : Fin 13) :
(x + y + z) ^ 2 = x ^ 2 + y ^ 2 + z ^ 2 + 2 * (x * y + y * z + z * x) := by
grind +ring
example (x y : Fin 17) : (x + y) ^ 3 = x ^ 3 + y ^ 3 + 3 * x * y * (x + y) := by
grind +ring
example (x y : Fin 19) : (x - y) * (x ^ 2 + x * y + y ^ 2) = x ^ 3 - y ^ 3 := by
grind +ring
```
---------
Co-authored-by: Kim Morrison <kim@tqft.net>
This PR fixes unintended inlining of `ToJson`, `FromJson`, and `Repr`
instances, which was causing exponential compilation times in `deriving`
clauses for large structures.
This PR contains the theorem proving that signed division x.toInt /
y.toInt only overflows when `x = intMin w` and `y = allOnes w` (for `0 <
w`).
To show that this is the *only* case in which overflow happens, we refer
to overflow for negation
(`BitVec.sdivOverflow_eq_negOverflow_of_neg_one`): in fact,
`x.toInt/(allOnes w).toInt = - x.toInt`, i.e., the overflow conditions
are the same as `negOverflow` for `x`, and then reason about the signs
of the operands with the respective theorems.
These BitVec theorems themselves rely on numerous `Int.ediv_*` theorems,
that carefully set the bounds of signed division for integers.
co-authored by @bollu, @tobiasgrosser
This PR adds `BitVec.pow` and `Pow (BitVec w) Nat`. The implementation
is the naive one, and should later be replaced by an `@[extern]`. This
is tracked at https://github.com/leanprover/lean4/issues/7887.
This PR adds SMT-LIB operators to detect overflow
`BitVec.(umul_overflow, smul_overflow)`, according to the definitions
[here](https://github.com/SMT-LIB/SMT-LIB-2/blob/2.7/Theories/FixedSizeBitVectors.smt2),
and the theorems proving equivalence of such definitions with the
`BitVec` library functions (`umulOverflow_eq`, `smulOverflow_eq`).
Support theorems for these proofs are `BitVec.toInt_one_of_lt,
BitVec.toInt_mul_toInt_lt, BitVec.le_toInt_mul_toInt,
BitVec.toNat_mul_toNat_lt, BitVec.two_pow_le_toInt_mul_toInt_iff,
BitVec.toInt_mul_toInt_lt_neg_two_pow_iff` and `Int.neg_mul_le_mul,
Int.bmod_eq_self_of_le_mul_two, Int.mul_le_mul_of_natAbs_le,
Int.mul_le_mul_of_le_of_le_of_nonneg_of_nonpos, Int.pow_lt_pow`. The PR
also includes a set of tests.
Co-authored by @tobiasgrosser.
---------
Co-authored-by: Tobias Grosser <tobias@grosser.es>
Co-authored-by: Tobias Grosser <github@grosser.es>
Co-authored-by: Siddharth <siddu.druid@gmail.com>
This PR makes the BitVec docstrings match each other and the rest of the
API in style.
---------
Co-authored-by: Markus Himmel <markus@himmel-villmar.de>
Co-authored-by: Siddharth <siddu.druid@gmail.com>
This PR adds SMT-LIB operators to detect overflow `BitVec.(usubOverflow,
ssubOverflow)`, according to the [SMTLIB
standard](https://github.com/SMT-LIB/SMT-LIB-2/blob/2.7/Theories/FixedSizeBitVectors.smt2),
and the theorems proving equivalence of such definition with the
`BitVec` library functions `BittVec.(usubOverflow_eq, ssubOverflow_eq)`.
Co-authored by @bollu.
---------
Co-authored-by: Siddharth <siddu.druid@gmail.com>
Co-authored-by: Alex Keizer <alex@keizer.dev>
This PR adds SMT-LIB operators to detect overflow `BitVec.negOverflow`,
according to the [SMTLIB
standard](https://github.com/SMT-LIB/SMT-LIB-2/blob/2.7/Theories/FixedSizeBitVectors.smt2),
and the theorem proving equivalence of such definition with the `BitVec`
library functions (`negOverflow_eq`).
Co-authored by @bollu and @alexkeizer
---------
Co-authored-by: Siddharth <siddu.druid@gmail.com>
This PR makes `BitVec.getElem` the simp normal form in case a proof is
available and changes `ext` to return `x[i]` + a hypothesis that proves
that we are in-bounds. This aligns `BitVec` further with the API
conventions of the Lean standard datatypes.
We move our proofs to this new normal form, which results in slightly
smaller proofs. With the exception of `getElem_ofFin`, no new API
surface is added as the `getElem` API has already been completed over
the previous months. We also move `getElem_shiftConcat_*` a bit higher
as they are needed in earlier proofs. To keep the changeset small, we do
not update the API of `BVDecide` but insert `←
BitVec.getLsbD_eq_getElem` at the few locations where it is needed.
Finally, we add a simproc for getElem, mirroring the existing ones for
getLsbD/getMsdD.
---------
Co-authored-by: Alex Keizer <alex@keizer.dev>
This PR adds SMT-LIB operators to detect overflow
`BitVec.(uadd_overflow, sadd_overflow)`, according to the definitions
[here](https://github.com/SMT-LIB/SMT-LIB-2/blob/2.7/Theories/FixedSizeBitVectors.smt2),
and the theorems proving equivalence of such definitions with the
`BitVec` library functions (`uaddOverflow_eq`, `saddOverflow_eq`).
Support theorems for these proofs are `BitVec.toNat_mod_cancel_of_lt,
BitVec.toInt_lt, BitVec.le_toInt, Int.bmod_neg_iff`. The PR also
includes a set of tests.
---------
Co-authored-by: Tobias Grosser <github@grosser.es>
Co-authored-by: Alex Keizer <alex@keizer.dev>
Co-authored-by: Tobias Grosser <tobias@grosser.es>
Co-authored-by: Siddharth Bhat <siddu.druid@gmail.com>
This PR adds simp lemmas replacing `BitVec.setWidth'` with `setWidth`,
and conditionally simplifying `setWidth v (setWidth w v)`.
---------
Co-authored-by: Tobias Grosser <tobias@grosser.es>
This PR defines `reverse` for bitvectors and implements a first subset
of theorems (`getLsbD_reverse, getMsbD_reverse, reverse_append,
reverse_replicate, reverse_cast, msb_reverse`). We also include some
necessary related theorems (`cons_append, cons_append_append,
append_assoc, replicate_append_self, replicate_succ'`) and deprecate
theorems`replicate_zero_eq` and `replicate_succ_eq`.
---------
Co-authored-by: Alex Keizer <alex@keizer.dev>
Co-authored-by: Kim Morrison <kim@tqft.net>
This PR adds `protected` to `Fin.cast` and `BitVec.cast`, to avoid
confusion with `_root_.cast`. These should mostly be used via
dot-notation in any case.
I made a few choices so far that can probably be discussed:
- got rid of `modn` on `UInt`, nobody seems to use it apart from the
definition of `shift` which can use normal `mod`
- removed the previous defeq optimized definition of `USize.size` in
favor for a normal one. The motivation was to allow `OfNat` to work
which doesn't seem to be necessary anymore afaict.
- Minimized uses of `.val`, should we maybe mark it deprecated?
- Mostly got rid of `.val` in basically all theorems as the proper next
level of API would now be `.toBitVec`. We could probably re-prove them
but it would be more annoying given the change of definition.
- Did not yet redefine `log2` in terms of `BitVec` as this would require
a `log2` in `BitVec` as well, do we want this?
- I added a couple of theorems around the relation of `<` on `UInt` and
`Nat`. These were previously not needed because defeq was used all over
the place to save us. I did not yet generalize these to all types as I
wasn't sure if they are the appropriate lemma that we want to have.
This follows the norm for all other Bitvector operations, and makes the
symbols `/` and `%` the simp normal form.
I'd imagine that @hargonix would prefer that this be merged after
https://github.com/leanprover/lean4/pull/5628, so as to prevent churn
for his PR. I'm happy to rebase the PR once the other PR lands.
---------
Co-authored-by: Henrik Böving <hargonix@gmail.com>
This PR adds the theorems
```
@[simp]
theorem divRec_zero (qr : DivModState w) :
divRec w w 0 n d qr = qr
@[simp]
theorem divRec_succ' (wn : Nat) (qr : DivModState w) :
divRec w wr (wn + 1) n d qr =
let r' := shiftConcat qr.r (n.getLsbD wn)
let input : DivModState w :=
if r' < d then ⟨qr.q.shiftConcat false, r'⟩ else ⟨qr.q.shiftConcat true, r' - d⟩
divRec w (wr + 1) wn n d input
```
The final statements may need some masasging to interoperate with
`bv_decide`. We prove the recurrence for unsigned division by building a
shift-subtract circuit, and then showing that this circuit obeys the
division algorithm's invariant.
---
A `DivModState` is lawful if the remainder width `wr` plus the dividend
width `wn` equals `w`,
and the bitvectors `r` and `n` have values in the bounds given by
bitwidths `wr`, resp. `wn`.
This is a proof engineering choice: An alternative world could have
`r : BitVec wr` and `n : BitVec wn`, but this required much more
dependent typing coercions.
Instead, we choose to declare all involved bitvectors as length `w`, and
then prove that
the values are within their respective bounds.
---------
Co-authored-by: Tobias Grosser <github@grosser.es>
Co-authored-by: Alex Keizer <alex@keizer.dev>
Co-authored-by: Kim Morrison <scott@tqft.net>
Co-authored-by: Tobias Grosser <tobias@grosser.es>
In LNSym we often use the pattern `ofBool (a.getLsbD i)` to pick out a
specific bit (`i`) from a bitvector (`a`).
By adding a rewrite to `extractLsb` to `bv_decide`s normalization set,
we can still automatically close goals that have this pattern. In the
process, I also added a simp-lemma about the value of a `Fin 1`.
