1// Copyright 2016 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
5package riscv64
6
7import (
8	"cmd/compile/internal/base"
9	"cmd/compile/internal/ir"
10	"cmd/compile/internal/objw"
11	"cmd/compile/internal/types"
12	"cmd/internal/obj"
13	"cmd/internal/obj/riscv"
14)
15
16func zeroRange(pp *objw.Progs, p *obj.Prog, off, cnt int64, _ *uint32) *obj.Prog {
17	if cnt == 0 {
18		return p
19	}
20
21	// Adjust the frame to account for LR.
22	off += base.Ctxt.Arch.FixedFrameSize
23
24	if cnt < int64(4*types.PtrSize) {
25		for i := int64(0); i < cnt; i += int64(types.PtrSize) {
26			p = pp.Append(p, riscv.AMOV, obj.TYPE_REG, riscv.REG_ZERO, 0, obj.TYPE_MEM, riscv.REG_SP, off+i)
27		}
28		return p
29	}
30
31	if cnt <= int64(128*types.PtrSize) {
32		p = pp.Append(p, riscv.AADDI, obj.TYPE_CONST, 0, off, obj.TYPE_REG, riscv.REG_X25, 0)
33		p.Reg = riscv.REG_SP
34		p = pp.Append(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_MEM, 0, 0)
35		p.To.Name = obj.NAME_EXTERN
36		p.To.Sym = ir.Syms.Duffzero
37		p.To.Offset = 8 * (128 - cnt/int64(types.PtrSize))
38		return p
39	}
40
41	// Loop, zeroing pointer width bytes at a time.
42	// ADD	$(off), SP, T0
43	// ADD	$(cnt), T0, T1
44	// loop:
45	// 	MOV	ZERO, (T0)
46	// 	ADD	$Widthptr, T0
47	//	BNE	T0, T1, loop
48	p = pp.Append(p, riscv.AADD, obj.TYPE_CONST, 0, off, obj.TYPE_REG, riscv.REG_T0, 0)
49	p.Reg = riscv.REG_SP
50	p = pp.Append(p, riscv.AADD, obj.TYPE_CONST, 0, cnt, obj.TYPE_REG, riscv.REG_T1, 0)
51	p.Reg = riscv.REG_T0
52	p = pp.Append(p, riscv.AMOV, obj.TYPE_REG, riscv.REG_ZERO, 0, obj.TYPE_MEM, riscv.REG_T0, 0)
53	loop := p
54	p = pp.Append(p, riscv.AADD, obj.TYPE_CONST, 0, int64(types.PtrSize), obj.TYPE_REG, riscv.REG_T0, 0)
55	p = pp.Append(p, riscv.ABNE, obj.TYPE_REG, riscv.REG_T0, 0, obj.TYPE_BRANCH, 0, 0)
56	p.Reg = riscv.REG_T1
57	p.To.SetTarget(loop)
58	return p
59}
60