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(*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*)
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(* Properties of the llair model *)
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open HolKernel boolLib bossLib Parse;
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open arithmeticTheory integerTheory integer_wordTheory wordsTheory;
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open settingsTheory miscTheory llairTheory;
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new_theory "llair_prop";
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numLib.prefer_num ();
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Theorem ifits_w2i:
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∀(w : 'a word). ifits (w2i w) (dimindex (:'a))
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Proof
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rw [ifits_def, GSYM INT_MIN_def] >>
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metis_tac [INT_MIN, w2i_ge, integer_wordTheory.INT_MAX_def, w2i_le,
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intLib.COOPER_PROVE ``!(x:int) y. x ≤ y - 1 ⇔ x < y``]
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QED
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Theorem truncate_2comp_fits:
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∀i size. 0 < size ⇒ ifits (truncate_2comp i size) size
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Proof
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rw [truncate_2comp_def, ifits_def] >>
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qmatch_goalsub_abbrev_tac `(i + s1) % s2` >>
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`s2 ≠ 0 ∧ ¬(s2 < 0)` by rw [Abbr `s2`]
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>- (
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`0 ≤ (i + s1) % s2` suffices_by intLib.COOPER_TAC >>
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drule INT_MOD_BOUNDS >>
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rw [])
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>- (
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`(i + s1) % s2 < 2 * s1` suffices_by intLib.COOPER_TAC >>
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`2 * s1 = s2` by rw [Abbr `s1`, Abbr `s2`, GSYM EXP] >>
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drule INT_MOD_BOUNDS >>
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rw [Abbr `s1`, Abbr `s2`])
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QED
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Theorem fits_ident:
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∀i size. 0 < size ⇒ (ifits i size ⇔ truncate_2comp i size = i)
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Proof
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rw [ifits_def, truncate_2comp_def] >>
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rw [intLib.COOPER_PROVE ``!(x:int) y z. x - y = z <=> x = y + z``] >>
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qmatch_goalsub_abbrev_tac `(_ + s1) % s2` >>
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`s2 ≠ 0 ∧ ¬(s2 < 0)` by rw [Abbr `s2`] >>
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`2 * s1 = s2` by rw [Abbr `s1`, Abbr `s2`, GSYM EXP] >>
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eq_tac >>
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rw []
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>- (
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simp [Once INT_ADD_COMM] >>
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irule INT_LESS_MOD >>
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rw [] >>
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intLib.COOPER_TAC)
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>- (
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`0 ≤ (i + s1) % (2 * s1)` suffices_by intLib.COOPER_TAC >>
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drule INT_MOD_BOUNDS >>
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simp [])
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>- (
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`(i + s1) % (2 * s1) < 2 * s1` suffices_by intLib.COOPER_TAC >>
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drule INT_MOD_BOUNDS >>
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simp [])
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QED
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Theorem i2n_n2i:
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!n size. 0 < size ⇒ (nfits n size ⇔ (i2n (n2i n size) = n))
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Proof
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rw [nfits_def, n2i_def, i2n_def] >> rw []
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>- intLib.COOPER_TAC
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>- (
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`2 ** size ≤ n` by intLib.COOPER_TAC >> simp [INT_SUB] >>
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Cases_on `n = 0` >> fs [] >>
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`n - 2 ** size < n` suffices_by intLib.COOPER_TAC >>
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irule SUB_LESS >> simp [])
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>- (
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`2 ** (size - 1) < 2 ** size` suffices_by intLib.COOPER_TAC >>
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fs [])
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QED
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Theorem n2i_i2n:
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!i size. 0 < size ⇒ (ifits i size ⇔ (n2i (i2n (IntV i size)) size) = IntV i size)
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Proof
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rw [ifits_def, n2i_def, i2n_def] >> rw [] >> fs []
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>- (
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eq_tac >> rw []
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>- (
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simp [intLib.COOPER_PROVE ``∀(x:int) y z. x - y = z ⇔ x = y + z``] >>
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`2 ** (size - 1) < 2 ** size` suffices_by intLib.COOPER_TAC >>
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fs [INT_OF_NUM])
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>- (
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fs [intLib.COOPER_PROVE ``∀(x:int) y z. x - y = z ⇔ x = y + z``] >>
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fs [INT_OF_NUM] >>
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`?j. i = -j` by intLib.COOPER_TAC >> rw [] >> fs [] >>
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qpat_x_assum `_ ≤ Num _` mp_tac >>
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fs [GSYM INT_OF_NUM] >>
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ASM_REWRITE_TAC [GSYM INT_LE] >> rw [] >>
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`2 ** size = 2 * 2 ** (size - 1)` by rw [GSYM EXP, ADD1] >> fs [] >>
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intLib.COOPER_TAC)
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>- intLib.COOPER_TAC)
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>- (
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eq_tac >> rw []
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>- intLib.COOPER_TAC
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>- intLib.COOPER_TAC >>
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`0 ≤ i` by intLib.COOPER_TAC >>
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fs [GSYM INT_OF_NUM] >>
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`&(2 ** size) = 0` by intLib.COOPER_TAC >>
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fs [])
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>- (
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eq_tac >> rw []
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>- (
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`2 ** size = 2 * 2 ** (size - 1)` by rw [GSYM EXP, ADD1] >> fs [] >>
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intLib.COOPER_TAC)
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>- intLib.COOPER_TAC
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>- intLib.COOPER_TAC)
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>- intLib.COOPER_TAC
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QED
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Theorem w2n_i2n:
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∀w. w2n (w : 'a word) = i2n (IntV (w2i w) (dimindex (:'a)))
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Proof
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rw [i2n_def] >> Cases_on `w` >> fs []
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>- (
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`INT_MIN (:α) ≤ n`
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by (
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fs [w2i_def] >> rw [] >>
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BasicProvers.EVERY_CASE_TAC >> fs [word_msb_n2w_numeric] >>
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rfs []) >>
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rw [w2i_n2w_neg, dimword_def, int_arithTheory.INT_NUM_SUB])
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>- (
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`n < INT_MIN (:'a)`
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by (
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fs [w2i_def] >> rw [] >>
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BasicProvers.EVERY_CASE_TAC >> fs [word_msb_n2w_numeric] >>
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rfs []) >>
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rw [w2i_n2w_pos])
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QED
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export_theory ();
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