1// Copyright (c) 2020 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build arm64 && gc && !purego
6
7#include "textflag.h"
8
9// carryPropagate works exactly like carryPropagateGeneric and uses the
10// same AND, ADD, and LSR+MADD instructions emitted by the compiler, but
11// avoids loading R0-R4 twice and uses LDP and STP.
12//
13// See https://golang.org/issues/43145 for the main compiler issue.
14//
15// func carryPropagate(v *Element)
16TEXT ·carryPropagate(SB),NOFRAME|NOSPLIT,$0-8
17 MOVD v+0(FP), R20
18
19 LDP 0(R20), (R0, R1)
20 LDP 16(R20), (R2, R3)
21 MOVD 32(R20), R4
22
23 AND $0x7ffffffffffff, R0, R10
24 AND $0x7ffffffffffff, R1, R11
25 AND $0x7ffffffffffff, R2, R12
26 AND $0x7ffffffffffff, R3, R13
27 AND $0x7ffffffffffff, R4, R14
28
29 ADD R0>>51, R11, R11
30 ADD R1>>51, R12, R12
31 ADD R2>>51, R13, R13
32 ADD R3>>51, R14, R14
33 // R4>>51 * 19 + R10 -> R10
34 LSR $51, R4, R21
35 MOVD $19, R22
36 MADD R22, R10, R21, R10
37
38 STP (R10, R11), 0(R20)
39 STP (R12, R13), 16(R20)
40 MOVD R14, 32(R20)
41
42 RET
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