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cmd/compile: add explanations to escape-analysis JSON/LSP logging

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For 1.15.

From the test:

{"range":{"start":{"line":7,"character":13},"end":{...},"severity":3,"code":"leaks","source":"go compiler","message":"parameter z leaks to ~r2 with derefs=0","relatedInformation":[
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":13},"end":{...}},"message":"escflow:    flow: y = z:"},
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":13},"end":{...}},"message":"escflow:      from y = \u003cN\u003e (assign-pair)"},
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":13},"end":{...}},"message":"escflow:    flow: ~r1 = y:"},
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":4,"character":11},"end":{...}},"message":"inlineLoc"},

	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":13},"end":{...}},"message":"escflow:      from y.b (dot of pointer)"},
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":4,"character":11},"end":{...}},"message":"inlineLoc"},

	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":13},"end":{...}},"message":"escflow:      from \u0026y.b (address-of)"},
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":4,"character":9},"end":...}},"message":"inlineLoc"},

	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":13},"end":{...}},"message":"escflow:      from ~r1 = \u003cN\u003e (assign-pair)"},
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":3},"end":...}},"message":"escflow:    flow: ~r2 = ~r1:"},
	{"location":{"uri":"file://T/file.go","range":{"start":{"line":9,"character":3},"end":...}},"message":"escflow:      from return (*int)(~r1) (return)"}]}

Change-Id: Idf02438801f63e487c35a928cf5a0b6d3cc48674
Reviewed-on: https://go-review.googlesource.com/c/go/+/206658
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
David Chase 2019-11-11 13:18:38 -05:00
parent fced302aa1
commit 06314b620d
3 changed files with 140 additions and 42 deletions
Download patch file Download diff file Expand all files Collapse all files

80
src/cmd/compile/internal/gc/escape.go
View file

@ -7,6 +7,7 @@ package gc
import (
"cmd/compile/internal/logopt"
"cmd/compile/internal/types"
"cmd/internal/src"
"fmt"
"math"
"strings"
@ -945,7 +946,7 @@ func (k EscHole) note(where *Node, why string) EscHole {
if where == nil || why == "" {
Fatalf("note: missing where/why")
}
if Debug['m'] >= 2 {
if Debug['m'] >= 2 || logopt.Enabled() {
k.notes = &EscNote{
next: k.notes,
where: where,
@ -1092,10 +1093,16 @@ func (e *Escape) flow(k EscHole, src *EscLocation) {
return
}
if dst.escapes && k.derefs < 0 { // dst = &src
if Debug['m'] >= 2 {
if Debug['m'] >= 2 || logopt.Enabled() {
pos := linestr(src.n.Pos)
fmt.Printf("%s: %v escapes to heap:\n", pos, src.n)
e.explainFlow(pos, dst, src, k.derefs, k.notes)
if Debug['m'] >= 2 {
fmt.Printf("%s: %v escapes to heap:\n", pos, src.n)
}
explanation := e.explainFlow(pos, dst, src, k.derefs, k.notes, []*logopt.LoggedOpt{})
if logopt.Enabled() {
logopt.LogOpt(src.n.Pos, "escapes", "escape", e.curfn.funcname(), fmt.Sprintf("%v escapes to heap", src.n), explanation)
}
}
src.escapes = true
return
@ -1187,9 +1194,15 @@ func (e *Escape) walkOne(root *EscLocation, walkgen uint32, enqueue func(*EscLoc
// that value flow for tagging the function
// later.
if l.isName(PPARAM) {
if Debug['m'] >= 2 && !l.escapes {
fmt.Printf("%s: parameter %v leaks to %s with derefs=%d:\n", linestr(l.n.Pos), l.n, e.explainLoc(root), base)
e.explainPath(root, l)
if (logopt.Enabled() || Debug['m'] >= 2) && !l.escapes {
if Debug['m'] >= 2 {
fmt.Printf("%s: parameter %v leaks to %s with derefs=%d:\n", linestr(l.n.Pos), l.n, e.explainLoc(root), base)
}
explanation := e.explainPath(root, l)
if logopt.Enabled() {
logopt.LogOpt(l.n.Pos, "leak", "escape", e.curfn.funcname(),
fmt.Sprintf("parameter %v leaks to %s with derefs=%d", l.n, e.explainLoc(root), base), explanation)
}
}
l.leakTo(root, base)
}
@ -1198,9 +1211,14 @@ func (e *Escape) walkOne(root *EscLocation, walkgen uint32, enqueue func(*EscLoc
// outlives it, then l needs to be heap
// allocated.
if addressOf && !l.escapes {
if Debug['m'] >= 2 {
fmt.Printf("%s: %v escapes to heap:\n", linestr(l.n.Pos), l.n)
e.explainPath(root, l)
if logopt.Enabled() || Debug['m'] >= 2 {
if Debug['m'] >= 2 {
fmt.Printf("%s: %v escapes to heap:\n", linestr(l.n.Pos), l.n)
}
explanation := e.explainPath(root, l)
if logopt.Enabled() {
logopt.LogOpt(l.n.Pos, "escape", "escape", e.curfn.funcname(), fmt.Sprintf("%v escapes to heap", l.n), explanation)
}
}
l.escapes = true
enqueue(l)
@ -1225,43 +1243,67 @@ func (e *Escape) walkOne(root *EscLocation, walkgen uint32, enqueue func(*EscLoc
}
// explainPath prints an explanation of how src flows to the walk root.
func (e *Escape) explainPath(root, src *EscLocation) {
func (e *Escape) explainPath(root, src *EscLocation) []*logopt.LoggedOpt {
visited := make(map[*EscLocation]bool)
pos := linestr(src.n.Pos)
var explanation []*logopt.LoggedOpt
for {
// Prevent infinite loop.
if visited[src] {
fmt.Printf("%s: warning: truncated explanation due to assignment cycle; see golang.org/issue/35518\n", pos)
if Debug['m'] >= 2 {
fmt.Printf("%s: warning: truncated explanation due to assignment cycle; see golang.org/issue/35518\n", pos)
}
break
}
visited[src] = true
dst := src.dst
edge := &dst.edges[src.dstEdgeIdx]
if edge.src != src {
Fatalf("path inconsistency: %v != %v", edge.src, src)
}
e.explainFlow(pos, dst, src, edge.derefs, edge.notes)
explanation = e.explainFlow(pos, dst, src, edge.derefs, edge.notes, explanation)
if dst == root {
break
}
src = dst
}
return explanation
}
func (e *Escape) explainFlow(pos string, dst, src *EscLocation, derefs int, notes *EscNote) {
func (e *Escape) explainFlow(pos string, dst, srcloc *EscLocation, derefs int, notes *EscNote, explanation []*logopt.LoggedOpt) []*logopt.LoggedOpt {
ops := "&"
if derefs >= 0 {
ops = strings.Repeat("*", derefs)
}
print := Debug['m'] >= 2
fmt.Printf("%s: flow: %s = %s%v:\n", pos, e.explainLoc(dst), ops, e.explainLoc(src))
for note := notes; note != nil; note = note.next {
fmt.Printf("%s: from %v (%v) at %s\n", pos, note.where, note.why, linestr(note.where.Pos))
flow := fmt.Sprintf(" flow: %s = %s%v:", e.explainLoc(dst), ops, e.explainLoc(srcloc))
if print {
fmt.Printf("%s:%s\n", pos, flow)
}
if logopt.Enabled() {
var epos src.XPos
if notes != nil {
epos = notes.where.Pos
} else if srcloc != nil && srcloc.n != nil {
epos = srcloc.n.Pos
}
explanation = append(explanation, logopt.NewLoggedOpt(epos, "escflow", "escape", e.curfn.funcname(), flow))
}
for note := notes; note != nil; note = note.next {
if print {
fmt.Printf("%s: from %v (%v) at %s\n", pos, note.where, note.why, linestr(note.where.Pos))
}
if logopt.Enabled() {
explanation = append(explanation, logopt.NewLoggedOpt(note.where.Pos, "escflow", "escape", e.curfn.funcname(),
fmt.Sprintf(" from %v (%v)", note.where, note.why)))
}
}
return explanation
}
func (e *Escape) explainLoc(l *EscLocation) string {