go marker 源码
golang marker 代码
文件路径：/src/cmd/compile/internal/dwarfgen/marker.go
// Copyright 2021 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 dwarfgen
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/internal/src"
)
// A ScopeMarker tracks scope nesting and boundaries for later use
// during DWARF generation.
type ScopeMarker struct {
parents []ir.ScopeID
marks []ir.Mark
}
// checkPos validates the given position and returns the current scope.
func (m *ScopeMarker) checkPos(pos src.XPos) ir.ScopeID {
if !pos.IsKnown() {
base.Fatalf("unknown scope position")
}
if len(m.marks) == 0 {
return 0
}
last := &m.marks[len(m.marks)-1]
if xposBefore(pos, last.Pos) {
base.FatalfAt(pos, "non-monotonic scope positions\n\t%v: previous scope position", base.FmtPos(last.Pos))
}
return last.Scope
}
// Push records a transition to a new child scope of the current scope.
func (m *ScopeMarker) Push(pos src.XPos) {
current := m.checkPos(pos)
m.parents = append(m.parents, current)
child := ir.ScopeID(len(m.parents))
m.marks = append(m.marks, ir.Mark{Pos: pos, Scope: child})
}
// Pop records a transition back to the current scope's parent.
func (m *ScopeMarker) Pop(pos src.XPos) {
current := m.checkPos(pos)
parent := m.parents[current-1]
m.marks = append(m.marks, ir.Mark{Pos: pos, Scope: parent})
}
// Unpush removes the current scope, which must be empty.
func (m *ScopeMarker) Unpush() {
i := len(m.marks) - 1
current := m.marks[i].Scope
if current != ir.ScopeID(len(m.parents)) {
base.FatalfAt(m.marks[i].Pos, "current scope is not empty")
}
m.parents = m.parents[:current-1]
m.marks = m.marks[:i]
}
// WriteTo writes the recorded scope marks to the given function,
// and resets the marker for reuse.
func (m *ScopeMarker) WriteTo(fn *ir.Func) {
m.compactMarks()
fn.Parents = make([]ir.ScopeID, len(m.parents))
copy(fn.Parents, m.parents)
m.parents = m.parents[:0]
fn.Marks = make([]ir.Mark, len(m.marks))
copy(fn.Marks, m.marks)
m.marks = m.marks[:0]
}
func (m *ScopeMarker) compactMarks() {
n := 0
for _, next := range m.marks {
if n > 0 && next.Pos == m.marks[n-1].Pos {
m.marks[n-1].Scope = next.Scope
continue
}
m.marks[n] = next
n++
}
m.marks = m.marks[:n]
}
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