cmd/compile: leave Pos unset for racewalk enter/exit

The locations chosen for racewalking inserted code can
be wrong and thus cause unwanted next/step behavior in
debuggers.  Forcing the positions to be unset results in
better behavior.

Test added, and test harness corrected to deal with
changes to gdb's output caused by -racewalk.

Incidental changes in Delve (not part of the usual testing,
but provided because we care about Delve) also reflected
in this CL.

Fixes #22600.

Change-Id: Idd0218afed52ab8c68efd9eabbdff3c92ea2b996
Reviewed-on: https://go-review.googlesource.com/78336
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Alessandro Arzilli <alessandro.arzilli@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -70,11 +70,15 @@ func instrument(fn *Node) {
 		nodpc := *nodfp
 		nodpc.Type = types.Types[TUINTPTR]
 		nodpc.Xoffset = int64(-Widthptr)
+		savedLineno := lineno
+		lineno = src.NoXPos
 		nd := mkcall("racefuncenter", nil, nil, &nodpc)
+
 		fn.Func.Enter.Prepend(nd)
 		nd = mkcall("racefuncexit", nil, nil)
 		fn.Func.Exit.Append(nd)
 		fn.Func.Dcl = append(fn.Func.Dcl, &nodpc)
+		lineno = savedLineno
 	}
 
 	if Debug['W'] != 0 {

src/cmd/compile/internal/ssa/debug_test.go

@@ -132,6 +132,9 @@ func TestNexting(t *testing.T) {
 	t.Run("dbg-"+debugger, func(t *testing.T) {
 		testNexting(t, "hist", "dbg", "-N -l")
 	})
+	t.Run("dbg-race-"+debugger, func(t *testing.T) {
+		testNexting(t, "i22600", "dbg-race", "-N -l", "-race")
+	})
 	t.Run("opt-"+debugger, func(t *testing.T) {
 		// If this is test is run with a runtime compiled with -N -l, it is very likely to fail.
 		// This occurs in the noopt builders (for example).
@@ -148,7 +151,7 @@ func TestNexting(t *testing.T) {
 	})
 }
 
-func testNexting(t *testing.T, base, tag, gcflags string) {
+func testNexting(t *testing.T, base, tag, gcflags string, moreArgs ...string) {
 	// (1) In testdata, build sample.go into sample
 	// (2) Run debugger gathering a history
 	// (3) Read expected history from testdata/sample.<variant>.nexts
@@ -171,7 +174,11 @@ func testNexting(t *testing.T, base, tag, gcflags string) {
 		defer os.RemoveAll(tmpdir)
 	}
 
-	runGo(t, "", "build", "-o", exe, "-gcflags=all="+gcflags, filepath.Join("testdata", base+".go"))
+	runGoArgs := []string{"build", "-o", exe, "-gcflags=all=" + gcflags}
+	runGoArgs = append(runGoArgs, moreArgs...)
+	runGoArgs = append(runGoArgs, filepath.Join("testdata", base+".go"))
+
+	runGo(t, "", runGoArgs...)
 
 	var h1 *nextHist
 	nextlog := logbase + "-" + debugger + ".nexts"
@@ -533,7 +540,7 @@ func newGdb(tag, executable string, args ...string) dbgr {
 	s := &gdbState{tag: tag, cmd: cmd, args: args}
 	s.atLineRe = regexp.MustCompile("(^|\n)([0-9]+)(.*)")
 	s.funcFileLinePCre = regexp.MustCompile(
-		"([^ ]+) [(][)][ \\t\\n]+at ([^:]+):([0-9]+)")
+		"([^ ]+) [(][^)]*[)][ \\t\\n]+at ([^:]+):([0-9]+)")
 	// runtime.main () at /Users/drchase/GoogleDrive/work/go/src/runtime/proc.go:201
 	//                                    function              file    line
 	// Thread 2 hit Breakpoint 1, main.main () at /Users/drchase/GoogleDrive/work/debug/hist.go:18

src/cmd/compile/internal/ssa/testdata/hist.opt-dlv.nexts

@@ -9,3 +9,98 @@
 63:		hist := make([]int, 7)                                //gdb-opt=(sink,dx/O,dy/O)
 64:		var reader io.Reader = strings.NewReader(cannedInput) //gdb-dbg=(hist/A,cannedInput/A)
 19:		"strings"
+65:		if len(os.Args) > 1 {
+14:		"bufio"
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+76:			i, err := strconv.ParseInt(s, 10, 64)
+77:			if err != nil { //gdb-dbg=(i) //gdb-opt=(err,hist,i)
+81:			hist = ensure(int(i), hist)
+82:			hist[int(i)]++
+74:		for scanner.Scan() { //gdb-opt=(scanner/A)
+86:		for i, a := range hist {
+87:			if a == 0 { //gdb-opt=(a,n,t)
+88:				continue
+87:			if a == 0 { //gdb-opt=(a,n,t)
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+91:			n += a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+86:		for i, a := range hist {
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+87:			if a == 0 { //gdb-opt=(a,n,t)
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+91:			n += a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+86:		for i, a := range hist {
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+87:			if a == 0 { //gdb-opt=(a,n,t)
+88:				continue
+87:			if a == 0 { //gdb-opt=(a,n,t)
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+91:			n += a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+86:		for i, a := range hist {
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+87:			if a == 0 { //gdb-opt=(a,n,t)
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+91:			n += a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+90:			t += i * a
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+86:		for i, a := range hist {
+92:			fmt.Fprintf(os.Stderr, "%d\t%d\t%d\t%d\t%d\n", i, a, n, i*a, t) //gdb-dbg=(n,i,t)
+87:			if a == 0 { //gdb-opt=(a,n,t)
+88:				continue

src/cmd/compile/internal/ssa/testdata/i22600.dbg-race-gdb.nexts

+  src/cmd/compile/internal/ssa/testdata/i22600.go
+8:	func main() {
+9:		pwd, err := os.Getwd()
+10:		if err != nil {
+14:		fmt.Println(pwd)
+15:	}

src/cmd/compile/internal/ssa/testdata/i22600.go

+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	pwd, err := os.Getwd()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	fmt.Println(pwd)
+}