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// Copyright 2017 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 gc
import (
"cmd/internal/dwarf"
"cmd/internal/obj"
"cmd/internal/src"
"sort"
)
// See golang.org/issue/20390.
func xposBefore(p, q src.XPos) bool {
return Ctxt.PosTable.Pos(p).Before(Ctxt.PosTable.Pos(q))
}
func findScope(marks []Mark, pos src.XPos) ScopeID {
i := sort.Search(len(marks), func(i int) bool {
return xposBefore(pos, marks[i].Pos)
})
if i == 0 {
return 0
}
return marks[i-1].Scope
}
func assembleScopes(fnsym *obj.LSym, fn *Node, dwarfVars []*dwarf.Var, varScopes []ScopeID) []dwarf.Scope {
// Initialize the DWARF scope tree based on lexical scopes.
dwarfScopes := make([]dwarf.Scope, 1+len(fn.Func.Parents))
for i, parent := range fn.Func.Parents {
dwarfScopes[i+1].Parent = int32(parent)
}
scopeVariables(dwarfVars, varScopes, dwarfScopes)
scopePCs(fnsym, fn.Func.Marks, dwarfScopes)
return compactScopes(dwarfScopes)
}
// scopeVariables assigns DWARF variable records to their scopes.
func scopeVariables(dwarfVars []*dwarf.Var, varScopes []ScopeID, dwarfScopes []dwarf.Scope) {
sort.Stable(varsByScopeAndOffset{dwarfVars, varScopes})
i0 := 0
for i := range dwarfVars {
if varScopes[i] == varScopes[i0] {
continue
}
dwarfScopes[varScopes[i0]].Vars = dwarfVars[i0:i]
i0 = i
}
if i0 < len(dwarfVars) {
dwarfScopes[varScopes[i0]].Vars = dwarfVars[i0:]
}
}
// scopePCs assigns PC ranges to their scopes.
func scopePCs(fnsym *obj.LSym, marks []Mark, dwarfScopes []dwarf.Scope) {
// If there aren't any child scopes (in particular, when scope
// tracking is disabled), we can skip a whole lot of work.
if len(marks) == 0 {
return
}
p0 := fnsym.Func.Text
scope := findScope(marks, p0.Pos)
for p := fnsym.Func.Text; p != nil; p = p.Link {
if p.Pos == p0.Pos {
continue
}
dwarfScopes[scope].AppendRange(dwarf.Range{Start: p0.Pc, End: p.Pc})
p0 = p
scope = findScope(marks, p0.Pos)
}
if p0.Pc < fnsym.Size {
dwarfScopes[scope].AppendRange(dwarf.Range{Start: p0.Pc, End: fnsym.Size})
}
}
func compactScopes(dwarfScopes []dwarf.Scope) []dwarf.Scope {
// Reverse pass to propagate PC ranges to parent scopes.
for i := len(dwarfScopes) - 1; i > 0; i-- {
s := &dwarfScopes[i]
dwarfScopes[s.Parent].UnifyRanges(s)
}
return dwarfScopes
}
type varsByScopeAndOffset struct {
vars []*dwarf.Var
scopes []ScopeID
}
func (v varsByScopeAndOffset) Len() int {
return len(v.vars)
}
func (v varsByScopeAndOffset) Less(i, j int) bool {
if v.scopes[i] != v.scopes[j] {
return v.scopes[i] < v.scopes[j]
}
return v.vars[i].StackOffset < v.vars[j].StackOffset
}
func (v varsByScopeAndOffset) Swap(i, j int) {
v.vars[i], v.vars[j] = v.vars[j], v.vars[i]
v.scopes[i], v.scopes[j] = v.scopes[j], v.scopes[i]
}
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