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cmd/compile: remove large intermediate slice from gc.scopePCs

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Three loops can be converted into one.
Minor reviewer-recommended refactoring.
Passes toolstash-check.

Updates #27739.

Change-Id: Ia87a11d88ae3ce56fcc4267fe6c5a9c13bf7f533
Reviewed-on: https://go-review.googlesource.com/c/go/+/176577
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Alessandro Arzilli <alessandro.arzilli@gmail.com>
This commit is contained in:
David Chase 2019-05-10 12:18:43 -04:00
parent 2fd97ee25e
commit d41a0a0690
2 changed files with 18 additions and 30 deletions
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34
src/cmd/compile/internal/gc/scope.go
View File

@ -55,14 +55,6 @@ func scopeVariables(dwarfVars []*dwarf.Var, varScopes []ScopeID, dwarfScopes []d
}
}
// A scopedPCs represents a non-empty half-open interval of PCs that
// share a common source position.
type scopedPCs struct {
start, end int64
pos src.XPos
scope ScopeID
}
// 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
@ -70,36 +62,18 @@ func scopePCs(fnsym *obj.LSym, marks []Mark, dwarfScopes []dwarf.Scope) {
if len(marks) == 0 {
return
}
// Break function text into scopedPCs.
var pcs []scopedPCs
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
}
if p0.Pc < p.Pc {
pcs = append(pcs, scopedPCs{start: p0.Pc, end: p.Pc, pos: p0.Pos})
}
dwarfScopes[scope].AppendRange(dwarf.Range{Start: p0.Pc, End: p.Pc})
p0 = p
scope = findScope(marks, p0.Pos)
}
if p0.Pc < fnsym.Size {
pcs = append(pcs, scopedPCs{start: p0.Pc, end: fnsym.Size, pos: p0.Pos})
}
// Assign scopes to each chunk of instructions.
for i := range pcs {
pcs[i].scope = findScope(marks, pcs[i].pos)
}
// Create sorted PC ranges for each DWARF scope.
for _, pc := range pcs {
r := &dwarfScopes[pc.scope].Ranges
if i := len(*r); i > 0 && (*r)[i-1].End == pc.start {
(*r)[i-1].End = pc.end
} else {
*r = append(*r, dwarf.Range{Start: pc.start, End: pc.end})
}
dwarfScopes[scope].AppendRange(dwarf.Range{Start: p0.Pc, End: fnsym.Size})
}
}

14
src/cmd/internal/dwarf/dwarf.go
View File

@ -145,6 +145,20 @@ func (s *Scope) UnifyRanges(c *Scope) {
s.Ranges = out
}
// AppendRange adds r to s, if r is non-empty.
// If possible, it extends the last Range in s.Ranges; if not, it creates a new one.
func (s *Scope) AppendRange(r Range) {
if r.End <= r.Start {
return
}
i := len(s.Ranges)
if i > 0 && s.Ranges[i-1].End == r.Start {
s.Ranges[i-1].End = r.End
return
}
s.Ranges = append(s.Ranges, r)
}
type InlCalls struct {
Calls []InlCall
}