Adding upstream version 1.18.10.upstream/1.18.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 808 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/logopt/escape.go b/src/cmd/compile/internal/logopt/escape.go
new file mode 100644
index 0000000..9660e93
--- /dev/null
+++ b/src/cmd/compile/internal/logopt/escape.go
@@ -0,0 +1,14 @@
+// Copyright 2019 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.
+
+//go:build go1.8
+// +build go1.8
+
+package logopt
+
+import "net/url"
+
+func pathEscape(s string) string {
+	return url.PathEscape(s)
+}
diff --git a/src/cmd/compile/internal/logopt/escape_bootstrap.go b/src/cmd/compile/internal/logopt/escape_bootstrap.go
new file mode 100644
index 0000000..cc04eaa
--- /dev/null
+++ b/src/cmd/compile/internal/logopt/escape_bootstrap.go
@@ -0,0 +1,13 @@
+// Copyright 2019 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.
+
+//go:build !go1.8
+// +build !go1.8
+
+package logopt
+
+// For bootstrapping with an early version of Go
+func pathEscape(s string) string {
+	panic("This should never be called; the compiler is not fully bootstrapped if it is.")
+}
diff --git a/src/cmd/compile/internal/logopt/log_opts.go b/src/cmd/compile/internal/logopt/log_opts.go
new file mode 100644
index 0000000..97ebf56
--- /dev/null
+++ b/src/cmd/compile/internal/logopt/log_opts.go
@@ -0,0 +1,523 @@
+// Copyright 2019 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 logopt
+
+import (
+	"cmd/internal/obj"
+	"cmd/internal/src"
+	"encoding/json"
+	"fmt"
+	"internal/buildcfg"
+	"io"
+	"log"
+	"net/url"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"unicode"
+)
+
+// This implements (non)optimization logging for -json option to the Go compiler
+// The option is -json 0,<destination>.
+//
+// 0 is the version number; to avoid the need for synchronized updates, if
+// new versions of the logging appear, the compiler will support both, for a while,
+// and clients will specify what they need.
+//
+// <destination> is a directory.
+// Directories are specified with a leading / or os.PathSeparator,
+// or more explicitly with file://directory.  The second form is intended to
+// deal with corner cases on Windows, and to allow specification of a relative
+// directory path (which is normally a bad idea, because the local directory
+// varies a lot in a build, especially with modules and/or vendoring, and may
+// not be writeable).
+//
+// For each package pkg compiled, a url.PathEscape(pkg)-named subdirectory
+// is created.  For each source file.go in that package that generates
+// diagnostics (no diagnostics means no file),
+// a url.PathEscape(file)+".json"-named file is created and contains the
+// logged diagnostics.
+//
+// For example, "cmd%2Finternal%2Fdwarf/%3Cautogenerated%3E.json"
+// for "cmd/internal/dwarf" and <autogenerated> (which is not really a file, but the compiler sees it)
+//
+// If the package string is empty, it is replaced internally with string(0) which encodes to %00.
+//
+// Each log file begins with a JSON record identifying version,
+// platform, and other context, followed by optimization-relevant
+// LSP Diagnostic records, one per line (LSP version 3.15, no difference from 3.14 on the subset used here
+// see https://microsoft.github.io/language-server-protocol/specifications/specification-3-15/ )
+//
+// The fields of a Diagnostic are used in the following way:
+// Range: the outermost source position, for now begin and end are equal.
+// Severity: (always) SeverityInformation (3)
+// Source: (always) "go compiler"
+// Code: a string describing the missed optimization, e.g., "nilcheck", "cannotInline", "isInBounds", "escape"
+// Message: depending on code, additional information, e.g., the reason a function cannot be inlined.
+// RelatedInformation: if the missed optimization actually occurred at a function inlined at Range,
+//    then the sequence of inlined locations appears here, from (second) outermost to innermost,
+//    each with message="inlineLoc".
+//
+//    In the case of escape analysis explanations, after any outer inlining locations,
+//    the lines of the explanation appear, each potentially followed with its own inlining
+//    location if the escape flow occurred within an inlined function.
+//
+// For example <destination>/cmd%2Fcompile%2Finternal%2Fssa/prove.json
+// might begin with the following line (wrapped for legibility):
+//
+// {"version":0,"package":"cmd/compile/internal/ssa","goos":"darwin","goarch":"amd64",
+//  "gc_version":"devel +e1b9a57852 Fri Nov 1 15:07:00 2019 -0400",
+//  "file":"/Users/drchase/work/go/src/cmd/compile/internal/ssa/prove.go"}
+//
+// and later contain (also wrapped for legibility):
+//
+// {"range":{"start":{"line":191,"character":24},"end":{"line":191,"character":24}},
+//  "severity":3,"code":"nilcheck","source":"go compiler","message":"",
+//  "relatedInformation":[
+//    {"location":{"uri":"file:///Users/drchase/work/go/src/cmd/compile/internal/ssa/func.go",
+//                 "range":{"start":{"line":153,"character":16},"end":{"line":153,"character":16}}},
+//     "message":"inlineLoc"}]}
+//
+// That is, at prove.go (implicit from context, provided in both filename and header line),
+// line 191, column 24, a nilcheck occurred in the generated code.
+// The relatedInformation indicates that this code actually came from
+// an inlined call to func.go, line 153, character 16.
+//
+// prove.go:191:
+// 	ft.orderS = f.newPoset()
+// func.go:152 and 153:
+//  func (f *Func) newPoset() *poset {
+//	    if len(f.Cache.scrPoset) > 0 {
+//
+// In the case that the package is empty, the string(0) package name is also used in the header record, for example
+//
+//  go tool compile -json=0,file://logopt x.go       # no -p option to set the package
+//  head -1 logopt/%00/x.json
+//  {"version":0,"package":"\u0000","goos":"darwin","goarch":"amd64","gc_version":"devel +86487adf6a Thu Nov 7 19:34:56 2019 -0500","file":"x.go"}
+
+type VersionHeader struct {
+	Version   int    `json:"version"`
+	Package   string `json:"package"`
+	Goos      string `json:"goos"`
+	Goarch    string `json:"goarch"`
+	GcVersion string `json:"gc_version"`
+	File      string `json:"file,omitempty"` // LSP requires an enclosing resource, i.e., a file
+}
+
+// DocumentURI, Position, Range, Location, Diagnostic, DiagnosticRelatedInformation all reuse json definitions from gopls.
+// See https://github.com/golang/tools/blob/22afafe3322a860fcd3d88448768f9db36f8bc5f/internal/lsp/protocol/tsprotocol.go
+
+type DocumentURI string
+
+type Position struct {
+	Line      uint `json:"line"`      // gopls uses float64, but json output is the same for integers
+	Character uint `json:"character"` // gopls uses float64, but json output is the same for integers
+}
+
+// A Range in a text document expressed as (zero-based) start and end positions.
+// A range is comparable to a selection in an editor. Therefore the end position is exclusive.
+// If you want to specify a range that contains a line including the line ending character(s)
+// then use an end position denoting the start of the next line.
+type Range struct {
+	/*Start defined:
+	 * The range's start position
+	 */
+	Start Position `json:"start"`
+
+	/*End defined:
+	 * The range's end position
+	 */
+	End Position `json:"end"` // exclusive
+}
+
+// A Location represents a location inside a resource, such as a line inside a text file.
+type Location struct {
+	// URI is
+	URI DocumentURI `json:"uri"`
+
+	// Range is
+	Range Range `json:"range"`
+}
+
+/* DiagnosticRelatedInformation defined:
+ * Represents a related message and source code location for a diagnostic. This should be
+ * used to point to code locations that cause or related to a diagnostics, e.g when duplicating
+ * a symbol in a scope.
+ */
+type DiagnosticRelatedInformation struct {
+
+	/*Location defined:
+	 * The location of this related diagnostic information.
+	 */
+	Location Location `json:"location"`
+
+	/*Message defined:
+	 * The message of this related diagnostic information.
+	 */
+	Message string `json:"message"`
+}
+
+// DiagnosticSeverity defines constants
+type DiagnosticSeverity uint
+
+const (
+	/*SeverityInformation defined:
+	 * Reports an information.
+	 */
+	SeverityInformation DiagnosticSeverity = 3
+)
+
+// DiagnosticTag defines constants
+type DiagnosticTag uint
+
+/*Diagnostic defined:
+ * Represents a diagnostic, such as a compiler error or warning. Diagnostic objects
+ * are only valid in the scope of a resource.
+ */
+type Diagnostic struct {
+
+	/*Range defined:
+	 * The range at which the message applies
+	 */
+	Range Range `json:"range"`
+
+	/*Severity defined:
+	 * The diagnostic's severity. Can be omitted. If omitted it is up to the
+	 * client to interpret diagnostics as error, warning, info or hint.
+	 */
+	Severity DiagnosticSeverity `json:"severity,omitempty"` // always SeverityInformation for optimizer logging.
+
+	/*Code defined:
+	 * The diagnostic's code, which usually appear in the user interface.
+	 */
+	Code string `json:"code,omitempty"` // LSP uses 'number | string' = gopls interface{}, but only string here, e.g. "boundsCheck", "nilcheck", etc.
+
+	/*Source defined:
+	 * A human-readable string describing the source of this
+	 * diagnostic, e.g. 'typescript' or 'super lint'. It usually
+	 * appears in the user interface.
+	 */
+	Source string `json:"source,omitempty"` // "go compiler"
+
+	/*Message defined:
+	 * The diagnostic's message. It usually appears in the user interface
+	 */
+	Message string `json:"message"` // sometimes used, provides additional information.
+
+	/*Tags defined:
+	 * Additional metadata about the diagnostic.
+	 */
+	Tags []DiagnosticTag `json:"tags,omitempty"` // always empty for logging optimizations.
+
+	/*RelatedInformation defined:
+	 * An array of related diagnostic information, e.g. when symbol-names within
+	 * a scope collide all definitions can be marked via this property.
+	 */
+	RelatedInformation []DiagnosticRelatedInformation `json:"relatedInformation,omitempty"`
+}
+
+// A LoggedOpt is what the compiler produces and accumulates,
+// to be converted to JSON for human or IDE consumption.
+type LoggedOpt struct {
+	pos          src.XPos      // Source code position at which the event occurred. If it is inlined, outer and all inlined locations will appear in JSON.
+	compilerPass string        // Compiler pass.  For human/adhoc consumption; does not appear in JSON (yet)
+	functionName string        // Function name.  For human/adhoc consumption; does not appear in JSON (yet)
+	what         string        // The (non) optimization; "nilcheck", "boundsCheck", "inline", "noInline"
+	target       []interface{} // Optional target(s) or parameter(s) of "what" -- what was inlined, why it was not, size of copy, etc. 1st is most important/relevant.
+}
+
+type logFormat uint8
+
+const (
+	None  logFormat = iota
+	Json0           // version 0 for LSP 3.14, 3.15; future versions of LSP may change the format and the compiler may need to support both as clients are updated.
+)
+
+var Format = None
+var dest string
+
+// LogJsonOption parses and validates the version,directory value attached to the -json compiler flag.
+func LogJsonOption(flagValue string) {
+	version, directory := parseLogFlag("json", flagValue)
+	if version != 0 {
+		log.Fatal("-json version must be 0")
+	}
+	dest = checkLogPath(directory)
+	Format = Json0
+}
+
+// parseLogFlag checks the flag passed to -json
+// for version,destination format and returns the two parts.
+func parseLogFlag(flag, value string) (version int, directory string) {
+	if Format != None {
+		log.Fatal("Cannot repeat -json flag")
+	}
+	commaAt := strings.Index(value, ",")
+	if commaAt <= 0 {
+		log.Fatalf("-%s option should be '<version>,<destination>' where <version> is a number", flag)
+	}
+	v, err := strconv.Atoi(value[:commaAt])
+	if err != nil {
+		log.Fatalf("-%s option should be '<version>,<destination>' where <version> is a number: err=%v", flag, err)
+	}
+	version = v
+	directory = value[commaAt+1:]
+	return
+}
+
+// isWindowsDriveURI returns true if the file URI is of the format used by
+// Windows URIs. The url.Parse package does not specially handle Windows paths
+// (see golang/go#6027), so we check if the URI path has a drive prefix (e.g. "/C:").
+// (copied from tools/internal/span/uri.go)
+// this is less comprehensive that the processing in filepath.IsAbs on Windows.
+func isWindowsDriveURIPath(uri string) bool {
+	if len(uri) < 4 {
+		return false
+	}
+	return uri[0] == '/' && unicode.IsLetter(rune(uri[1])) && uri[2] == ':'
+}
+
+func parseLogPath(destination string) (string, string) {
+	if filepath.IsAbs(destination) {
+		return filepath.Clean(destination), ""
+	}
+	if strings.HasPrefix(destination, "file://") { // IKWIAD, or Windows C:\foo\bar\baz
+		uri, err := url.Parse(destination)
+		if err != nil {
+			return "", fmt.Sprintf("optimizer logging destination looked like file:// URI but failed to parse: err=%v", err)
+		}
+		destination = uri.Host + uri.Path
+		if isWindowsDriveURIPath(destination) {
+			// strip leading / from /C:
+			// unlike tools/internal/span/uri.go, do not uppercase the drive letter -- let filepath.Clean do what it does.
+			destination = destination[1:]
+		}
+		return filepath.Clean(destination), ""
+	}
+	return "", fmt.Sprintf("optimizer logging destination %s was neither %s-prefixed directory nor file://-prefixed file URI", destination, string(filepath.Separator))
+}
+
+// checkLogPath does superficial early checking of the string specifying
+// the directory to which optimizer logging is directed, and if
+// it passes the test, stores the string in LO_dir
+func checkLogPath(destination string) string {
+	path, complaint := parseLogPath(destination)
+	if complaint != "" {
+		log.Fatalf(complaint)
+	}
+	err := os.MkdirAll(path, 0755)
+	if err != nil {
+		log.Fatalf("optimizer logging destination '<version>,<directory>' but could not create <directory>: err=%v", err)
+	}
+	return path
+}
+
+var loggedOpts []*LoggedOpt
+var mu = sync.Mutex{} // mu protects loggedOpts.
+
+// NewLoggedOpt allocates a new LoggedOpt, to later be passed to either NewLoggedOpt or LogOpt as "args".
+// Pos is the source position (including inlining), what is the message, pass is which pass created the message,
+// funcName is the name of the function
+// A typical use for this to accumulate an explanation for a missed optimization, for example, why did something escape?
+func NewLoggedOpt(pos src.XPos, what, pass, funcName string, args ...interface{}) *LoggedOpt {
+	pass = strings.Replace(pass, " ", "_", -1)
+	return &LoggedOpt{pos, pass, funcName, what, args}
+}
+
+// Logopt logs information about a (usually missed) optimization performed by the compiler.
+// Pos is the source position (including inlining), what is the message, pass is which pass created the message,
+// funcName is the name of the function
+func LogOpt(pos src.XPos, what, pass, funcName string, args ...interface{}) {
+	if Format == None {
+		return
+	}
+	lo := NewLoggedOpt(pos, what, pass, funcName, args...)
+	mu.Lock()
+	defer mu.Unlock()
+	// Because of concurrent calls from back end, no telling what the order will be, but is stable-sorted by outer Pos before use.
+	loggedOpts = append(loggedOpts, lo)
+}
+
+// Enabled returns whether optimization logging is enabled.
+func Enabled() bool {
+	switch Format {
+	case None:
+		return false
+	case Json0:
+		return true
+	}
+	panic("Unexpected optimizer-logging level")
+}
+
+// byPos sorts diagnostics by source position.
+type byPos struct {
+	ctxt *obj.Link
+	a    []*LoggedOpt
+}
+
+func (x byPos) Len() int { return len(x.a) }
+func (x byPos) Less(i, j int) bool {
+	return x.ctxt.OutermostPos(x.a[i].pos).Before(x.ctxt.OutermostPos(x.a[j].pos))
+}
+func (x byPos) Swap(i, j int) { x.a[i], x.a[j] = x.a[j], x.a[i] }
+
+func writerForLSP(subdirpath, file string) io.WriteCloser {
+	basename := file
+	lastslash := strings.LastIndexAny(basename, "\\/")
+	if lastslash != -1 {
+		basename = basename[lastslash+1:]
+	}
+	lastdot := strings.LastIndex(basename, ".go")
+	if lastdot != -1 {
+		basename = basename[:lastdot]
+	}
+	basename = pathEscape(basename)
+
+	// Assume a directory, make a file
+	p := filepath.Join(subdirpath, basename+".json")
+	w, err := os.Create(p)
+	if err != nil {
+		log.Fatalf("Could not create file %s for logging optimizer actions, %v", p, err)
+	}
+	return w
+}
+
+func fixSlash(f string) string {
+	if os.PathSeparator == '/' {
+		return f
+	}
+	return strings.Replace(f, string(os.PathSeparator), "/", -1)
+}
+
+func uriIfy(f string) DocumentURI {
+	url := url.URL{
+		Scheme: "file",
+		Path:   fixSlash(f),
+	}
+	return DocumentURI(url.String())
+}
+
+// Return filename, replacing a first occurrence of $GOROOT with the
+// actual value of the GOROOT (because LSP does not speak "$GOROOT").
+func uprootedPath(filename string) string {
+	if !strings.HasPrefix(filename, "$GOROOT/") {
+		return filename
+	}
+	return buildcfg.GOROOT + filename[len("$GOROOT"):]
+}
+
+// FlushLoggedOpts flushes all the accumulated optimization log entries.
+func FlushLoggedOpts(ctxt *obj.Link, slashPkgPath string) {
+	if Format == None {
+		return
+	}
+
+	sort.Stable(byPos{ctxt, loggedOpts}) // Stable is necessary to preserve the per-function order, which is repeatable.
+	switch Format {
+
+	case Json0: // LSP 3.15
+		var posTmp []src.Pos
+		var encoder *json.Encoder
+		var w io.WriteCloser
+
+		if slashPkgPath == "" {
+			slashPkgPath = "\000"
+		}
+		subdirpath := filepath.Join(dest, pathEscape(slashPkgPath))
+		err := os.MkdirAll(subdirpath, 0755)
+		if err != nil {
+			log.Fatalf("Could not create directory %s for logging optimizer actions, %v", subdirpath, err)
+		}
+		diagnostic := Diagnostic{Source: "go compiler", Severity: SeverityInformation}
+
+		// For LSP, make a subdirectory for the package, and for each file foo.go, create foo.json in that subdirectory.
+		currentFile := ""
+		for _, x := range loggedOpts {
+			posTmp, p0 := x.parsePos(ctxt, posTmp)
+			p0f := uprootedPath(p0.Filename())
+
+			if currentFile != p0f {
+				if w != nil {
+					w.Close()
+				}
+				currentFile = p0f
+				w = writerForLSP(subdirpath, currentFile)
+				encoder = json.NewEncoder(w)
+				encoder.Encode(VersionHeader{Version: 0, Package: slashPkgPath, Goos: buildcfg.GOOS, Goarch: buildcfg.GOARCH, GcVersion: buildcfg.Version, File: currentFile})
+			}
+
+			// The first "target" is the most important one.
+			var target string
+			if len(x.target) > 0 {
+				target = fmt.Sprint(x.target[0])
+			}
+
+			diagnostic.Code = x.what
+			diagnostic.Message = target
+			diagnostic.Range = newPointRange(p0)
+			diagnostic.RelatedInformation = diagnostic.RelatedInformation[:0]
+
+			appendInlinedPos(posTmp, &diagnostic)
+
+			// Diagnostic explanation is stored in RelatedInformation after inlining info
+			if len(x.target) > 1 {
+				switch y := x.target[1].(type) {
+				case []*LoggedOpt:
+					for _, z := range y {
+						posTmp, p0 := z.parsePos(ctxt, posTmp)
+						loc := newLocation(p0)
+						msg := z.what
+						if len(z.target) > 0 {
+							msg = msg + ": " + fmt.Sprint(z.target[0])
+						}
+
+						diagnostic.RelatedInformation = append(diagnostic.RelatedInformation, DiagnosticRelatedInformation{Location: loc, Message: msg})
+						appendInlinedPos(posTmp, &diagnostic)
+					}
+				}
+			}
+
+			encoder.Encode(diagnostic)
+		}
+		if w != nil {
+			w.Close()
+		}
+	}
+}
+
+// newPointRange returns a single-position Range for the compiler source location p.
+func newPointRange(p src.Pos) Range {
+	return Range{Start: Position{p.Line(), p.Col()},
+		End: Position{p.Line(), p.Col()}}
+}
+
+// newLocation returns the Location for the compiler source location p
+func newLocation(p src.Pos) Location {
+	loc := Location{URI: uriIfy(uprootedPath(p.Filename())), Range: newPointRange(p)}
+	return loc
+}
+
+// appendInlinedPos extracts inlining information from posTmp and append it to diagnostic
+func appendInlinedPos(posTmp []src.Pos, diagnostic *Diagnostic) {
+	for i := 1; i < len(posTmp); i++ {
+		p := posTmp[i]
+		loc := newLocation(p)
+		diagnostic.RelatedInformation = append(diagnostic.RelatedInformation, DiagnosticRelatedInformation{Location: loc, Message: "inlineLoc"})
+	}
+}
+
+func (x *LoggedOpt) parsePos(ctxt *obj.Link, posTmp []src.Pos) ([]src.Pos, src.Pos) {
+	posTmp = ctxt.AllPos(x.pos, posTmp)
+	// Reverse posTmp to put outermost first.
+	l := len(posTmp)
+	for i := 0; i < l/2; i++ {
+		posTmp[i], posTmp[l-i-1] = posTmp[l-i-1], posTmp[i]
+	}
+	p0 := posTmp[0]
+	return posTmp, p0
+}
diff --git a/src/cmd/compile/internal/logopt/logopt_test.go b/src/cmd/compile/internal/logopt/logopt_test.go
new file mode 100644
index 0000000..902cbc8
--- /dev/null
+++ b/src/cmd/compile/internal/logopt/logopt_test.go
@@ -0,0 +1,258 @@
+// Copyright 2019 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 logopt
+
+import (
+	"internal/testenv"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+const srcCode = `package x
+type pair struct {a,b int}
+func bar(y *pair) *int {
+	return &y.b
+}
+var a []int
+func foo(w, z *pair) *int {
+	if *bar(w) > 0 {
+		return bar(z)
+	}
+	if a[1] > 0 {
+		a = a[:2]
+	}
+	return &a[0]
+}
+
+// address taking prevents closure inlining
+func n() int {
+	foo := func() int { return 1 }
+	bar := &foo
+	x := (*bar)() + foo()
+	return x
+}
+`
+
+func want(t *testing.T, out string, desired string) {
+	// On Windows, Unicode escapes in the JSON output end up "normalized" elsewhere to /u....,
+	// so "normalize" what we're looking for to match that.
+	s := strings.ReplaceAll(desired, string(os.PathSeparator), "/")
+	if !strings.Contains(out, s) {
+		t.Errorf("did not see phrase %s in \n%s", s, out)
+	}
+}
+
+func wantN(t *testing.T, out string, desired string, n int) {
+	if strings.Count(out, desired) != n {
+		t.Errorf("expected exactly %d occurrences of %s in \n%s", n, desired, out)
+	}
+}
+
+func TestPathStuff(t *testing.T) {
+	sep := string(filepath.Separator)
+	if path, whine := parseLogPath("file:///c:foo"); path != "c:foo" || whine != "" { // good path
+		t.Errorf("path='%s', whine='%s'", path, whine)
+	}
+	if path, whine := parseLogPath("file:///foo"); path != sep+"foo" || whine != "" { // good path
+		t.Errorf("path='%s', whine='%s'", path, whine)
+	}
+	if path, whine := parseLogPath("foo"); path != "" || whine == "" { // BAD path
+		t.Errorf("path='%s', whine='%s'", path, whine)
+	}
+	if sep == "\\" { // On WINDOWS ONLY
+		if path, whine := parseLogPath("C:/foo"); path != "C:\\foo" || whine != "" { // good path
+			t.Errorf("path='%s', whine='%s'", path, whine)
+		}
+		if path, whine := parseLogPath("c:foo"); path != "" || whine == "" { // BAD path
+			t.Errorf("path='%s', whine='%s'", path, whine)
+		}
+		if path, whine := parseLogPath("/foo"); path != "" || whine == "" { // BAD path
+			t.Errorf("path='%s', whine='%s'", path, whine)
+		}
+	} else { // ON UNIX ONLY
+		if path, whine := parseLogPath("/foo"); path != sep+"foo" || whine != "" { // good path
+			t.Errorf("path='%s', whine='%s'", path, whine)
+		}
+	}
+}
+
+func TestLogOpt(t *testing.T) {
+	t.Parallel()
+
+	testenv.MustHaveGoBuild(t)
+
+	dir, err := ioutil.TempDir("", "TestLogOpt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	dir = fixSlash(dir) // Normalize the directory name as much as possible, for Windows testing
+	src := filepath.Join(dir, "file.go")
+	if err := ioutil.WriteFile(src, []byte(srcCode), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	outfile := filepath.Join(dir, "file.o")
+
+	t.Run("JSON_fails", func(t *testing.T) {
+		// Test malformed flag
+		out, err := testLogOpt(t, "-json=foo", src, outfile)
+		if err == nil {
+			t.Error("-json=foo succeeded unexpectedly")
+		}
+		want(t, out, "option should be")
+		want(t, out, "number")
+
+		// Test a version number that is currently unsupported (and should remain unsupported for a while)
+		out, err = testLogOpt(t, "-json=9,foo", src, outfile)
+		if err == nil {
+			t.Error("-json=0,foo succeeded unexpectedly")
+		}
+		want(t, out, "version must be")
+
+	})
+
+	// replace d (dir)  with t ("tmpdir") and convert path separators to '/'
+	normalize := func(out []byte, d, t string) string {
+		s := string(out)
+		s = strings.ReplaceAll(s, d, t)
+		s = strings.ReplaceAll(s, string(os.PathSeparator), "/")
+		return s
+	}
+
+	// Ensure that <128 byte copies are not reported and that 128-byte copies are.
+	// Check at both 1 and 8-byte alignments.
+	t.Run("Copy", func(t *testing.T) {
+		const copyCode = `package x
+func s128a1(x *[128]int8) [128]int8 {
+	return *x
+}
+func s127a1(x *[127]int8) [127]int8 {
+	return *x
+}
+func s16a8(x *[16]int64) [16]int64 {
+	return *x
+}
+func s15a8(x *[15]int64) [15]int64 {
+	return *x
+}
+`
+		copy := filepath.Join(dir, "copy.go")
+		if err := ioutil.WriteFile(copy, []byte(copyCode), 0644); err != nil {
+			t.Fatal(err)
+		}
+		outcopy := filepath.Join(dir, "copy.o")
+
+		// On not-amd64, test the host architecture and os
+		arches := []string{runtime.GOARCH}
+		goos0 := runtime.GOOS
+		if runtime.GOARCH == "amd64" { // Test many things with "linux" (wasm will get "js")
+			arches = []string{"arm", "arm64", "386", "amd64", "mips", "mips64", "ppc64le", "riscv64", "s390x", "wasm"}
+			goos0 = "linux"
+		}
+
+		for _, arch := range arches {
+			t.Run(arch, func(t *testing.T) {
+				goos := goos0
+				if arch == "wasm" {
+					goos = "js"
+				}
+				_, err := testCopy(t, dir, arch, goos, copy, outcopy)
+				if err != nil {
+					t.Error("-json=0,file://log/opt should have succeeded")
+				}
+				logged, err := ioutil.ReadFile(filepath.Join(dir, "log", "opt", "x", "copy.json"))
+				if err != nil {
+					t.Error("-json=0,file://log/opt missing expected log file")
+				}
+				slogged := normalize(logged, string(uriIfy(dir)), string(uriIfy("tmpdir")))
+				t.Logf("%s", slogged)
+				want(t, slogged, `{"range":{"start":{"line":3,"character":2},"end":{"line":3,"character":2}},"severity":3,"code":"copy","source":"go compiler","message":"128 bytes"}`)
+				want(t, slogged, `{"range":{"start":{"line":9,"character":2},"end":{"line":9,"character":2}},"severity":3,"code":"copy","source":"go compiler","message":"128 bytes"}`)
+				wantN(t, slogged, `"code":"copy"`, 2)
+			})
+		}
+	})
+
+	// Some architectures don't fault on nil dereference, so nilchecks are eliminated differently.
+	// The N-way copy test also doesn't need to run N-ways N times.
+	if runtime.GOARCH != "amd64" {
+		return
+	}
+
+	t.Run("Success", func(t *testing.T) {
+		// This test is supposed to succeed
+
+		// Note 'file://' is the I-Know-What-I-Am-Doing way of specifying a file, also to deal with corner cases for Windows.
+		_, err := testLogOptDir(t, dir, "-json=0,file://log/opt", src, outfile)
+		if err != nil {
+			t.Error("-json=0,file://log/opt should have succeeded")
+		}
+		logged, err := ioutil.ReadFile(filepath.Join(dir, "log", "opt", "x", "file.json"))
+		if err != nil {
+			t.Error("-json=0,file://log/opt missing expected log file")
+		}
+		// All this delicacy with uriIfy and filepath.Join is to get this test to work right on Windows.
+		slogged := normalize(logged, string(uriIfy(dir)), string(uriIfy("tmpdir")))
+		t.Logf("%s", slogged)
+		// below shows proper nilcheck
+		want(t, slogged, `{"range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}},"severity":3,"code":"nilcheck","source":"go compiler","message":"",`+
+			`"relatedInformation":[{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":4,"character":11},"end":{"line":4,"character":11}}},"message":"inlineLoc"}]}`)
+		want(t, slogged, `{"range":{"start":{"line":11,"character":6},"end":{"line":11,"character":6}},"severity":3,"code":"isInBounds","source":"go compiler","message":""}`)
+		want(t, slogged, `{"range":{"start":{"line":7,"character":6},"end":{"line":7,"character":6}},"severity":3,"code":"canInlineFunction","source":"go compiler","message":"cost: 35"}`)
+		// escape analysis explanation
+		want(t, slogged, `{"range":{"start":{"line":7,"character":13},"end":{"line":7,"character":13}},"severity":3,"code":"leak","source":"go compiler","message":"parameter z leaks to ~r0 with derefs=0",`+
+			`"relatedInformation":[`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}}},"message":"escflow:    flow: y = z:"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}}},"message":"escflow:      from y := z (assign-pair)"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}}},"message":"escflow:    flow: ~R0 = y:"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":4,"character":11},"end":{"line":4,"character":11}}},"message":"inlineLoc"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}}},"message":"escflow:      from y.b (dot of pointer)"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":4,"character":11},"end":{"line":4,"character":11}}},"message":"inlineLoc"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}}},"message":"escflow:      from \u0026y.b (address-of)"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":4,"character":9},"end":{"line":4,"character":9}}},"message":"inlineLoc"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":13},"end":{"line":9,"character":13}}},"message":"escflow:      from ~R0 = \u0026y.b (assign-pair)"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":3},"end":{"line":9,"character":3}}},"message":"escflow:    flow: ~r0 = ~R0:"},`+
+			`{"location":{"uri":"file://tmpdir/file.go","range":{"start":{"line":9,"character":3},"end":{"line":9,"character":3}}},"message":"escflow:      from return ~R0 (return)"}]}`)
+	})
+}
+
+func testLogOpt(t *testing.T, flag, src, outfile string) (string, error) {
+	run := []string{testenv.GoToolPath(t), "tool", "compile", flag, "-o", outfile, src}
+	t.Log(run)
+	cmd := exec.Command(run[0], run[1:]...)
+	out, err := cmd.CombinedOutput()
+	t.Logf("%s", out)
+	return string(out), err
+}
+
+func testLogOptDir(t *testing.T, dir, flag, src, outfile string) (string, error) {
+	// Notice the specified import path "x"
+	run := []string{testenv.GoToolPath(t), "tool", "compile", "-p", "x", flag, "-o", outfile, src}
+	t.Log(run)
+	cmd := exec.Command(run[0], run[1:]...)
+	cmd.Dir = dir
+	out, err := cmd.CombinedOutput()
+	t.Logf("%s", out)
+	return string(out), err
+}
+
+func testCopy(t *testing.T, dir, goarch, goos, src, outfile string) (string, error) {
+	// Notice the specified import path "x"
+	run := []string{testenv.GoToolPath(t), "tool", "compile", "-p", "x", "-json=0,file://log/opt", "-o", outfile, src}
+	t.Log(run)
+	cmd := exec.Command(run[0], run[1:]...)
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "GOARCH="+goarch, "GOOS="+goos)
+	out, err := cmd.CombinedOutput()
+	t.Logf("%s", out)
+	return string(out), err
+}