cmd/compile: add support for telemetry

Add cmd/internal/telemetry to cmd/dist's bootstrapDirs so it's built
when bootstrapping the compiler. cmd/internal/telemetry is a wrapper
arount telemetry functions that stubs out the functions when built in
bootstrap mode to avoid dependencies on x/telemetry in bootstrap mode.

Call telemetry.Start with an empty config to open the counter file, and
increment a counter for when the command is invoked.

After flags are parsed, increment a counter for each of the names of the
flags that were passed in. The counter names will be compile/flag:<name>
so for example we'll have compile/flag:e and compile/flag:E.

In FatalfAt, increment a stack counter for internal errors.

For #58894

Change-Id: Ia5a8a63aa43b2276641181626cbfbea7e4647faa
Reviewed-on: https://go-review.googlesource.com/c/go/+/570679
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/cmd/compile/internal/base/flag.go

@@ -6,6 +6,7 @@ package base
 
 import (
 	"cmd/internal/cov/covcmd"
+	"cmd/internal/telemetry"
 	"encoding/json"
 	"flag"
 	"fmt"
@@ -193,6 +194,7 @@ func ParseFlags() {
 	objabi.AddVersionFlag() // -V
 	registerFlags()
 	objabi.Flagparse(usage)
+	telemetry.CountFlags("compile/flag:", *flag.CommandLine)
 
 	if gcd := os.Getenv("GOCOMPILEDEBUG"); gcd != "" {
 		// This will only override the flags set in gcd;

src/cmd/compile/internal/base/print.go

@@ -14,6 +14,7 @@ import (
 	"strings"
 
 	"cmd/internal/src"
+	"cmd/internal/telemetry"
 )
 
 // An errorMsg is a queued error message, waiting to be printed.
@@ -194,6 +195,8 @@ func Fatalf(format string, args ...interface{}) {
 	FatalfAt(Pos, format, args...)
 }
 
+var bugStack = telemetry.NewStackCounter("compile/bug", 16) // 16 is arbitrary; used by gopls and crashmonitor
+
 // FatalfAt reports a fatal error - an internal problem - at pos and exits.
 // If other errors have already been printed, then FatalfAt just quietly exits.
 // (The internal problem may have been caused by incomplete information
@@ -209,6 +212,8 @@ func Fatalf(format string, args ...interface{}) {
 func FatalfAt(pos src.XPos, format string, args ...interface{}) {
 	FlushErrors()
 
+	bugStack.Inc()
+
 	if Debug.Panic != 0 || numErrors == 0 {
 		fmt.Printf("%v: internal compiler error: ", FmtPos(pos))
 		fmt.Printf(format, args...)

src/cmd/compile/internal/gc/main.go

@@ -30,6 +30,7 @@ import (
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"cmd/internal/src"
+	"cmd/internal/telemetry"
 	"flag"
 	"fmt"
 	"internal/buildcfg"
@@ -58,6 +59,8 @@ func handlePanic() {
 // code, and finally writes the compiled package definition to disk.
 func Main(archInit func(*ssagen.ArchInfo)) {
 	base.Timer.Start("fe", "init")
+	telemetry.Start()
+	telemetry.Inc("compile/invocations")
 
 	defer handlePanic()
 

src/cmd/dist/buildtool.go

@@ -52,6 +52,7 @@ var bootstrapDirs = []string{
 	"cmd/internal/quoted",
 	"cmd/internal/src",
 	"cmd/internal/sys",
+	"cmd/internal/telemetry",
 	"cmd/link",
 	"cmd/link/internal/...",
 	"compress/flate",