[dev.regabi] cmd/compile: split out package dwarfgen [generated]

[git-generate]
cd src/cmd/compile/internal/gc

rf '
	# Inline and remove ngotype.
	ex {
		import "cmd/compile/internal/ir"
		import "cmd/compile/internal/reflectdata"
		var n ir.Node
		ngotype(n) -> reflectdata.TypeSym(n.Type())
	}
	rm ngotype

	mv recordFlags RecordFlags
	mv recordPackageName RecordPackageName
	mv RecordFlags RecordPackageName dwarf.go

	mv debuginfo Info
	mv genAbstractFunc AbstractFunc
	mv scope.go scope_test.go dwarf.go dwinl.go cmd/compile/internal/dwarfgen
'

Change-Id: I31fa982900dbba2066ca4c7a706af922e5481c70
Reviewed-on: https://go-review.googlesource.com/c/go/+/279477
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 112 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/dwarfgen/scope.go b/src/cmd/compile/internal/dwarfgen/scope.go
new file mode 100644
index 0000000000..1c040edc28
--- /dev/null
+++ b/src/cmd/compile/internal/dwarfgen/scope.go
@@ -0,0 +1,112 @@
+// 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 dwarfgen
+
+import (
+	"sort"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/internal/dwarf"
+	"cmd/internal/obj"
+	"cmd/internal/src"
+)
+
+// See golang.org/issue/20390.
+func xposBefore(p, q src.XPos) bool {
+	return base.Ctxt.PosTable.Pos(p).Before(base.Ctxt.PosTable.Pos(q))
+}
+
+func findScope(marks []ir.Mark, pos src.XPos) ir.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 *ir.Func, dwarfVars []*dwarf.Var, varScopes []ir.ScopeID) []dwarf.Scope {
+	// Initialize the DWARF scope tree based on lexical scopes.
+	dwarfScopes := make([]dwarf.Scope, 1+len(fn.Parents))
+	for i, parent := range fn.Parents {
+		dwarfScopes[i+1].Parent = int32(parent)
+	}
+
+	scopeVariables(dwarfVars, varScopes, dwarfScopes)
+	scopePCs(fnsym, fn.Marks, dwarfScopes)
+	return compactScopes(dwarfScopes)
+}
+
+// scopeVariables assigns DWARF variable records to their scopes.
+func scopeVariables(dwarfVars []*dwarf.Var, varScopes []ir.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 []ir.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 := p0; 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 []ir.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]
+}