golang location 代码
文件路径：/src/cmd/compile/internal/ssa/location.go
/ 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
import (
"cmd/compile/internal/ir"
"cmd/compile/internal/types"
"fmt"
)
/ A place that an ssa variable can reside.
type Location interface {
String() string / name to use in assembly templates: AX, 16(SP), ...
}
/ A Register is a machine register, like AX.
/ They are numbered densely from 0 (for each architecture).
type Register struct {
num int32 / dense numbering
objNum int16 / register number from cmd/internal/obj/$ARCH
gcNum int16 / GC register map number (dense numbering of registers that can contain pointers)
name string
}
func (r *Register) String() string {
return r.name
}
/ ObjNum returns the register number from cmd/internal/obj/$ARCH that
/ corresponds to this register.
func (r *Register) ObjNum() int16 {
return r.objNum
}
/ GCNum returns the runtime GC register index of r, or -1 if this
/ register can't contain pointers.
func (r *Register) GCNum() int16 {
return r.gcNum
}
/ A LocalSlot is a location in the stack frame, which identifies and stores
/ part or all of a PPARAM, PPARAMOUT, or PAUTO ONAME node.
/ It can represent a whole variable, part of a larger stack slot, or part of a
/ variable that has been decomposed into multiple stack slots.
/ As an example, a string could have the following configurations:
/
/ stack layout LocalSlots
/
/ Optimizations are disabled. s is on the stack and represented in its entirety.
/ [ ------- s string ---- ] { N: s, Type: string, Off: 0 }
/
/ s was not decomposed, but the SSA operates on its parts individually, so
/ there is a LocalSlot for each of its fields that points into the single stack slot.
/ [ ------- s string ---- ] { N: s, Type: *uint8, Off: 0 }, {N: s, Type: int, Off: 8}
/
/ s was decomposed. Each of its fields is in its own stack slot and has its own LocalSLot.
/ [ ptr *uint8 ] [ len int] { N: ptr, Type: *uint8, Off: 0, SplitOf: parent, SplitOffset: 0},
/ { N: len, Type: int, Off: 0, SplitOf: parent, SplitOffset: 8}
/ parent = &{N: s, Type: string}
type LocalSlot struct {
N *ir.Name / an ONAME *ir.Name representing a stack location.
Type *types.Type / type of slot
Off int64 / offset of slot in N
SplitOf *LocalSlot / slot is a decomposition of SplitOf
SplitOffset int64 / .. at this offset.
}
func (s LocalSlot) String() string {
if s.Off == 0 {
return fmt.Sprintf("%v[%v]", s.N, s.Type)
}
return fmt.Sprintf("%v+%d[%v]", s.N, s.Off, s.Type)
}
type LocPair [2]Location
func (t LocPair) String() string {
n0, n1 := "nil", "nil"
if t[0] != nil {
n0 = t[0].String()
}
if t[1] != nil {
n1 = t[1].String()
}
return fmt.Sprintf("<%s,%s>", n0, n1)
}
type LocResults []Location
func (t LocResults) String() string {
s := ""
a := "<"
for _, r := range t {
a += s
s = ","
a += r.String()
}
a += ">"
return a
}
type Spill struct {
Type *types.Type
Offset int64
Reg int16
}