all: remove pre-Go 1.17 workarounds

The Go bootstrap toolchain requirement is now Go 1.17.
We can finally delete all these pre-Go 1.17 workarounds.

For golang#44505.

Change-Id: I59d4dff1cde23da022892b5b6a116eb3dbad9ce4
Reviewed-on: https://go-review.googlesource.com/c/go/+/420903
Auto-Submit: Dmitri Shuralyov <[email protected]>
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: rsc

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

@@ -8,12 +8,11 @@ import (
 	"os"
 	"runtime"
 	"runtime/pprof"
+	tracepkg "runtime/trace"
 
 	"cmd/compile/internal/base"
 )
 
-var traceHandler func(string)
-
 func startProfile() {
 	if base.Flag.CPUProfile != "" {
 		f, err := os.Create(base.Flag.CPUProfile)
@@ -64,13 +63,20 @@ func startProfile() {
 		if err != nil {
 			base.Fatalf("%v", err)
 		}
-		startMutexProfiling()
+		runtime.SetMutexProfileFraction(1)
 		base.AtExit(func() {
 			pprof.Lookup("mutex").WriteTo(f, 0)
 			f.Close()
 		})
 	}
-	if base.Flag.TraceProfile != "" && traceHandler != nil {
-		traceHandler(base.Flag.TraceProfile)
+	if base.Flag.TraceProfile != "" {
+		f, err := os.Create(base.Flag.TraceProfile)
+		if err != nil {
+			base.Fatalf("%v", err)
+		}
+		if err := tracepkg.Start(f); err != nil {
+			base.Fatalf("%v", err)
+		}
+		base.AtExit(tracepkg.Stop)
 	}
 }

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

@@ -376,7 +376,7 @@ func writerForLSP(subdirpath, file string) io.WriteCloser {
 	if lastdot != -1 {
 		basename = basename[:lastdot]
 	}
-	basename = pathEscape(basename)
+	basename = url.PathEscape(basename)
 
 	// Assume a directory, make a file
 	p := filepath.Join(subdirpath, basename+".json")
@@ -428,7 +428,7 @@ func FlushLoggedOpts(ctxt *obj.Link, slashPkgPath string) {
 		if slashPkgPath == "" {
 			slashPkgPath = "\000"
 		}
-		subdirpath := filepath.Join(dest, pathEscape(slashPkgPath))
+		subdirpath := filepath.Join(dest, url.PathEscape(slashPkgPath))
 		err := os.MkdirAll(subdirpath, 0755)
 		if err != nil {
 			log.Fatalf("Could not create directory %s for logging optimizer actions, %v", subdirpath, err)

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

@@ -6,6 +6,7 @@ package pkgbits
 
 import (
 	"fmt"
+	"runtime"
 	"strings"
 )
 
@@ -23,6 +24,24 @@ func fmtFrames(pcs ...uintptr) []string {
 
 type frameVisitor func(file string, line int, name string, offset uintptr)
 
+// walkFrames calls visit for each call frame represented by pcs.
+//
+// pcs should be a slice of PCs, as returned by runtime.Callers.
+func walkFrames(pcs []uintptr, visit frameVisitor) {
+	if len(pcs) == 0 {
+		return
+	}
+
+	frames := runtime.CallersFrames(pcs)
+	for {
+		frame, more := frames.Next()
+		visit(frame.File, frame.Line, frame.Function, frame.PC-frame.Entry)
+		if !more {
+			return
+		}
+	}
+}
+
 // SyncMarker is an enum type that represents markers that may be
 // written to export data to ensure the reader and writer stay
 // synchronized.

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

@@ -4,7 +4,10 @@
 
 package sort
 
-import "math/bits"
+import (
+	"internal/reflectlite"
+	"math/bits"
+)
 
 // Slice sorts the slice x given the provided less function.
 // It panics if x is not a slice.
@@ -16,8 +19,8 @@ import "math/bits"
 // The less function must satisfy the same requirements as
 // the Interface type's Less method.
 func Slice(x any, less func(i, j int) bool) {
-	rv := reflectValueOf(x)
-	swap := reflectSwapper(x)
+	rv := reflectlite.ValueOf(x)
+	swap := reflectlite.Swapper(x)
 	length := rv.Len()
 	limit := bits.Len(uint(length))
 	pdqsort_func(lessSwap{less, swap}, 0, length, limit)
@@ -30,15 +33,15 @@ func Slice(x any, less func(i, j int) bool) {
 // The less function must satisfy the same requirements as
 // the Interface type's Less method.
 func SliceStable(x any, less func(i, j int) bool) {
-	rv := reflectValueOf(x)
-	swap := reflectSwapper(x)
+	rv := reflectlite.ValueOf(x)
+	swap := reflectlite.Swapper(x)
 	stable_func(lessSwap{less, swap}, rv.Len())
 }
 
 // SliceIsSorted reports whether the slice x is sorted according to the provided less function.
 // It panics if x is not a slice.
 func SliceIsSorted(x any, less func(i, j int) bool) bool {
-	rv := reflectValueOf(x)
+	rv := reflectlite.ValueOf(x)
 	n := rv.Len()
 	for i := n - 1; i > 0; i-- {
 		if less(i, i-1) {