diff options
author | Jason Gross <jgross@mit.edu> | 2017-04-08 11:12:21 -0400 |
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committer | Jason Gross <jgross@mit.edu> | 2017-04-08 11:12:21 -0400 |
commit | 676d72059269e349bf731968fa15070dad41b9ac (patch) | |
tree | 240f3d508e219b6b0130c67e00c9be08ea45760e | |
parent | 7e68f242814aadf91e5b81a9f6c0a6236040b8dd (diff) |
Add ZToWord_wordToZ_ZToWord_small
-rw-r--r-- | src/Util/FixedWordSizesEquality.v | 20 | ||||
-rw-r--r-- | src/Util/WordUtil.v | 25 |
2 files changed, 45 insertions, 0 deletions
diff --git a/src/Util/FixedWordSizesEquality.v b/src/Util/FixedWordSizesEquality.v index e1a8f1f79..c8f37c86b 100644 --- a/src/Util/FixedWordSizesEquality.v +++ b/src/Util/FixedWordSizesEquality.v @@ -129,6 +129,18 @@ Proof. reflexivity. Qed. +Lemma ZToWord_gen_wordToZ_gen_ZToWord_gen_small : forall {sz1 sz2} v, + (wordToZ_gen (@ZToWord_gen sz2 v) < 2^(Z.of_nat sz1))%Z + -> @ZToWord_gen sz2 (wordToZ_gen (@ZToWord_gen sz1 v)) = ZToWord_gen v. +Proof. + unfold ZToWord_gen, wordToZ_gen. + intros sz1 sz2 v H. + change 2%Z with (Z.of_nat 2) in H. + rewrite <- !nat_N_Z, <- N2Z.inj_pow, <- N2Z.inj_lt in H. + rewrite N2Z.id, NToWord_wordToN_NToWord_small by assumption. + reflexivity. +Qed. + Lemma wordToZ_gen_ZToWord_gen_wordToZ_gen sz1 sz2 w : (sz1 <= sz2)%nat -> wordToZ_gen (@ZToWord_gen sz2 (@wordToZ_gen sz1 w)) = wordToZ_gen w. Proof. @@ -171,6 +183,14 @@ Proof. handle_le. Qed. +Lemma ZToWord_wordToZ_ZToWord_small : forall {sz1 sz2} v, + (wordToZ (@ZToWord sz2 v) < 2^Z.of_nat (2^sz1))%Z -> @ZToWord sz2 (wordToZ (@ZToWord sz1 v)) = ZToWord v. +Proof. + unfold wordToZ, ZToWord, word_case_dep. + intros sz1 sz2; break_match; intros; apply ZToWord_gen_wordToZ_gen_ZToWord_gen_small; + handle_le; try omega. +Qed. + Lemma wordToZ_ZToWord_wordToZ : forall sz1 sz2 w, (sz1 <= sz2)%nat -> wordToZ (@ZToWord sz2 (@wordToZ sz1 w)) = wordToZ w. Proof. unfold wordToZ, ZToWord, word_case_dep. diff --git a/src/Util/WordUtil.v b/src/Util/WordUtil.v index 4833f0df6..fc1ac28a6 100644 --- a/src/Util/WordUtil.v +++ b/src/Util/WordUtil.v @@ -414,6 +414,31 @@ Section WordToN. reflexivity. } } Qed. + Lemma NToWord_wordToN_NToWord_small : forall sz1 sz2 w, + (wordToN (NToWord sz2 w) < 2^N.of_nat sz1)%N + -> NToWord sz2 (wordToN (NToWord sz1 w)) = NToWord sz2 w. + Proof. + intros sz1 sz2 w H. + apply wbit_inj_iff_lt; intros k Hlt. + rewrite !wbit_NToWord, wordToN_testbit, wbit_NToWord, Nat2N.id. + destruct (N.eq_dec (wordToN (NToWord sz2 w)) 0) as [H'|H']; + [ apply N.bits_inj_iff in H'; specialize (H' (N.of_nat k)); + rewrite wordToN_testbit, wbit_NToWord, N2Nat.id, Nat2N.id in H'; simpl in * + | assert (H'' : sz1 <= k -> N.testbit (wordToN (NToWord sz2 w)) (N.of_nat k) = false); + [ intro; + apply N.log2_lt_pow2 in H; [ | lia.. ] + | rewrite wordToN_testbit, wbit_NToWord, N2Nat.id, Nat2N.id in H'' ] ]; + break_match; try reflexivity; + repeat match goal with + | [ H : (_ <? _) = true |- _ ] => apply Nat.ltb_lt in H + | [ H : (_ <? _) = false |- _ ] => apply Nat.ltb_ge in H + | _ => omega + | _ => congruence + | _ => rewrite N.bits_above_log2 by lia + | _ => solve [ symmetry; auto ] + end. + Qed. + Lemma NToWord_wordToN_NToWord : forall sz1 sz2 w, sz2 <= sz1 -> NToWord sz2 (wordToN (NToWord sz1 w)) = NToWord sz2 w. Proof. |