diff options
author | Jason Gross <jgross@mit.edu> | 2019-04-02 17:51:17 -0400 |
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committer | Jason Gross <jgross@mit.edu> | 2019-04-02 17:51:17 -0400 |
commit | ef3ce824f87fd11eed78a13a884579499a8ffc53 (patch) | |
tree | a6af1f34cffc7dedee718e263f6e5d2751eaf28c /src/Util | |
parent | bacfa270c0c492ef8518d360d87e46cee292474f (diff) |
Add Z.combine_at_bitwidth
Diffstat (limited to 'src/Util')
-rw-r--r-- | src/Util/ZUtil/Combine.v | 34 | ||||
-rw-r--r-- | src/Util/ZUtil/Definitions.v | 3 |
2 files changed, 37 insertions, 0 deletions
diff --git a/src/Util/ZUtil/Combine.v b/src/Util/ZUtil/Combine.v new file mode 100644 index 000000000..3ac4179c5 --- /dev/null +++ b/src/Util/ZUtil/Combine.v @@ -0,0 +1,34 @@ +Require Import Coq.Classes.Morphisms. +Require Import Coq.ZArith.ZArith. +Require Import Coq.micromega.Lia. +Require Import Crypto.Util.ZUtil.Definitions. +Require Import Crypto.Util.ZUtil.Tactics.DivModToQuotRem. +Require Import Crypto.Util.ZUtil.Notations. +Local Open Scope Z_scope. + +Module Z. + Lemma combine_at_bitwidth_correct bitwidth lo hi + : Z.combine_at_bitwidth bitwidth lo hi = lo + (hi << bitwidth). + Proof. reflexivity. Qed. + + Lemma combine_at_bitwidth_Proper bitwidth + : Proper (Z.le ==> Z.le ==> Z.le) (Z.combine_at_bitwidth bitwidth). + Proof. + cbv [Proper respectful]; intros; rewrite !combine_at_bitwidth_correct. + destruct bitwidth as [|bitwidth|bitwidth]; + [ | assert (0 <= 2^Z.pos bitwidth) by (apply Z.pow_nonneg; lia).. ]; + rewrite ?Z.shiftl_mul_pow2, ?Z.shiftl_div_pow2, ?Z.pow_0_r by lia; cbn [Z.opp]; try nia; + Z.div_mod_to_quot_rem; nia. + Qed. + Hint Resolve combine_at_bitwidth_Proper : zarith. + + Lemma combine_at_bitwidth_Proper1 bitwidth x + : Proper (Z.le ==> Z.le) (Z.combine_at_bitwidth bitwidth x). + Proof. repeat intro; eapply combine_at_bitwidth_Proper; (eassumption + reflexivity). Qed. + Hint Resolve combine_at_bitwidth_Proper1 : zarith. + + Lemma combine_at_bitwidth_Proper2 bitwidth x + : Proper (Z.le ==> Z.le) (fun y => Z.combine_at_bitwidth bitwidth y x). + Proof. repeat intro; eapply combine_at_bitwidth_Proper; (eassumption + reflexivity). Qed. + Hint Resolve combine_at_bitwidth_Proper2 : zarith. +End Z. diff --git a/src/Util/ZUtil/Definitions.v b/src/Util/ZUtil/Definitions.v index 8fe5772f5..a5ac1a95b 100644 --- a/src/Util/ZUtil/Definitions.v +++ b/src/Util/ZUtil/Definitions.v @@ -85,6 +85,9 @@ Module Z. then mul_split_at_bitwidth (Z.log2 s) x y else ((x * y) mod s, (x * y) / s). + Definition combine_at_bitwidth (bitwidth lo hi : Z) : Z + := lo + (hi << bitwidth). + (** if positive, round up to 2^k-1 (0b11111....); if negative, round down to -2^k (0b...111000000...) *) Definition round_lor_land_bound (x : Z) : Z := if (0 <=? x)%Z |