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// Copyright 2015 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 ssa
// stackalloc allocates storage in the stack frame for
// all Values that did not get a register.
func stackalloc(f *Func) {
home := f.RegAlloc
// Start with space for callee arguments/returns.
var n int64
for _, b := range f.Blocks {
if b.Kind != BlockCall {
continue
}
v := b.Control
if n < v.AuxInt {
n = v.AuxInt
}
}
// TODO: group variables by ptr/nonptr, size, etc. Emit ptr vars last
// so stackmap is smaller.
// Assign stack locations to phis first, because we
// must also assign the same locations to the phi copies
// introduced during regalloc.
for _, b := range f.Blocks {
for _, v := range b.Values {
if v.Op != OpPhi {
continue
}
if v.Type.IsMemory() { // TODO: only "regallocable" types
continue
}
n = align(n, v.Type.Alignment())
loc := &LocalSlot{n}
n += v.Type.Size()
home = setloc(home, v, loc)
for _, w := range v.Args {
home = setloc(home, w, loc)
}
}
}
// Now do all other unassigned values.
for _, b := range f.Blocks {
for _, v := range b.Values {
if v.ID < ID(len(home)) && home[v.ID] != nil {
continue
}
if v.Type.IsMemory() { // TODO: only "regallocable" types
continue
}
if len(v.Args) == 0 {
// v will have been materialized wherever it is needed.
continue
}
if len(v.Args) == 1 && (v.Args[0].Op == OpSP || v.Args[0].Op == OpSB) {
continue
}
n = align(n, v.Type.Alignment())
loc := &LocalSlot{n}
n += v.Type.Size()
home = setloc(home, v, loc)
}
}
// Finally, allocate space for all autos that we used
for _, b := range f.Blocks {
for _, v := range b.Values {
s, ok := v.Aux.(*AutoSymbol)
if !ok || s.Offset >= 0 {
continue
}
t := s.Typ
n = align(n, t.Alignment())
s.Offset = n
n += t.Size()
}
}
n = align(n, f.Config.ptrSize)
n += f.Config.ptrSize // space for return address. TODO: arch-dependent
f.RegAlloc = home
f.FrameSize = n
// TODO: share stack slots among noninterfering (& gc type compatible) values
}
// align increases n to the next multiple of a. a must be a power of 2.
func align(n int64, a int64) int64 {
return (n + a - 1) &^ (a - 1)
}
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