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|
------------------------------------------------------------------------
-- Agda Helium
--
-- Implementation of Barrett reduction.
------------------------------------------------------------------------
{-# OPTIONS --safe --without-K #-}
module Helium.Instructions.Instances.Barrett where
open import Data.Bool using (false)
open import Data.Sum using (inj₁)
open import Data.Vec using ([])
open import Data.Vec.Relation.Unary.All using ([])
open import Helium.Instructions.Base
open import Helium.Instructions.Core
-- Given:
-- m = ⌊ (1 << l) * n⁻¹ ⌋
-- -n = n
-- n < 2 ^ 32
-- | z | < 2 ^ 31
-- Computes:
-- z mod n
barret : (m -n : Expression [] (bits 32)) (t z : VecReg) (im : GenReg) → Procedure []
barret m -n t z im =
index R (lit (im ′f)) ≔ m ∙
invoke vqrdmulh-s32,t,z,m (tup []) ∙
index R (lit (im ′f)) ≔ -n ∙
invoke vmla-s32,z,t,-n (tup []) ∙end
where
vqrdmulh-s32,t,z,m =
ExecBeats (vqrdmulh (record
{ size = 32bit
; dest = t
; src₁ = z
; src₂ = inj₁ im
}))
vmla-s32,z,t,-n =
ExecBeats (vmla (record
{ size = 32bit
; unsigned = false
; acc = z
; src₁ = t
; src₂ = im
}))
|
