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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package s390x
import (
"cmd/compile/internal/gc"
"cmd/internal/obj"
"cmd/internal/obj/s390x"
)
// clearLoopCutOff is the (somewhat arbitrary) value above which it is better
// to have a loop of clear instructions (e.g. XCs) rather than just generating
// multiple instructions (i.e. loop unrolling).
// Must be between 256 and 4096.
const clearLoopCutoff = 1024
// zerorange clears the stack in the given range.
func zerorange(pp *gc.Progs, p *obj.Prog, off, cnt int64, _ *uint32) *obj.Prog {
if cnt == 0 {
return p
}
// Adjust the frame to account for LR.
off += gc.Ctxt.FixedFrameSize()
reg := int16(s390x.REGSP)
// If the off cannot fit in a 12-bit unsigned displacement then we
// need to create a copy of the stack pointer that we can adjust.
// We also need to do this if we are going to loop.
if off < 0 || off > 4096-clearLoopCutoff || cnt > clearLoopCutoff {
p = pp.Appendpp(p, s390x.AADD, obj.TYPE_CONST, 0, off, obj.TYPE_REG, s390x.REGRT1, 0)
p.Reg = int16(s390x.REGSP)
reg = s390x.REGRT1
off = 0
}
// Generate a loop of large clears.
if cnt > clearLoopCutoff {
n := cnt - (cnt % 256)
end := int16(s390x.REGRT2)
p = pp.Appendpp(p, s390x.AADD, obj.TYPE_CONST, 0, off+n, obj.TYPE_REG, end, 0)
p.Reg = reg
p = pp.Appendpp(p, s390x.ACLEAR, obj.TYPE_CONST, 0, 256, obj.TYPE_MEM, reg, off)
pl := p
p = pp.Appendpp(p, s390x.AADD, obj.TYPE_CONST, 0, 256, obj.TYPE_REG, reg, 0)
p = pp.Appendpp(p, s390x.ACMP, obj.TYPE_REG, reg, 0, obj.TYPE_REG, end, 0)
p = pp.Appendpp(p, s390x.ABNE, obj.TYPE_NONE, 0, 0, obj.TYPE_BRANCH, 0, 0)
gc.Patch(p, pl)
cnt -= n
}
// Generate remaining clear instructions without a loop.
for cnt > 0 {
n := cnt
// Can clear at most 256 bytes per instruction.
if n > 256 {
n = 256
}
switch n {
// Handle very small clears with move instructions.
case 8, 4, 2, 1:
ins := s390x.AMOVB
switch n {
case 8:
ins = s390x.AMOVD
case 4:
ins = s390x.AMOVW
case 2:
ins = s390x.AMOVH
}
p = pp.Appendpp(p, ins, obj.TYPE_CONST, 0, 0, obj.TYPE_MEM, reg, off)
// Handle clears that would require multiple move instructions with CLEAR (assembled as XC).
default:
p = pp.Appendpp(p, s390x.ACLEAR, obj.TYPE_CONST, 0, n, obj.TYPE_MEM, reg, off)
}
cnt -= n
off += n
}
return p
}
func zeroAuto(pp *gc.Progs, n *gc.Node) {
// Note: this code must not clobber any registers or the
// condition code.
sym := n.Sym.Linksym()
size := n.Type.Size()
for i := int64(0); i < size; i += int64(gc.Widthptr) {
p := pp.Prog(s390x.AMOVD)
p.From.Type = obj.TYPE_CONST
p.From.Offset = 0
p.To.Type = obj.TYPE_MEM
p.To.Name = obj.NAME_AUTO
p.To.Reg = s390x.REGSP
p.To.Offset = n.Xoffset + i
p.To.Sym = sym
}
}
func ginsnop(pp *gc.Progs) *obj.Prog {
return pp.Prog(s390x.ANOPH)
}