[dev.regabi] cmd/compile: finish cleanup of Debug parsing

Now that the debug settings are in a struct, use struct tags to set
the usage messages and use reflection to populate debugtab,
much like we did for the Flag struct.

Change-Id: Id2ba30c30a9158c062527715a68bf4dd94679457
Reviewed-on: https://go-review.googlesource.com/c/go/+/272247
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -2,149 +2,176 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Debug arguments, set by -d flag.
+
 package gc
 
 import (
 	"fmt"
 	"log"
 	"os"
+	"reflect"
 	"strconv"
 	"strings"
 
-	"cmd/compile/internal/ssa"
 	"cmd/internal/objabi"
 )
 
-// Debug arguments.
+// Debug holds the parsed debugging configuration values.
-// These can be specified with the -d flag, as in "-d nil"
+var Debug = DebugFlags{
-// to set the debug_checknil variable.
+	Fieldtrack: &objabi.Fieldtrack_enabled,
-// Multiple options can be comma-separated.
+}
-// Each option accepts an optional argument, as in "gcprog=2"
+
-var debugtab = []struct {
+// DebugFlags defines the debugging configuration values (see var Debug).
+// Each struct field is a different value, named for the lower-case of the field name.
+// Each field must be an int or string and must have a `help` struct tag.
+//
+// The -d option takes a comma-separated list of settings.
+// Each setting is name=value; for ints, name is short for name=1.
+type DebugFlags struct {
+	Append        int    `help:"print information about append compilation"`
+	Checkptr      int    `help:"instrument unsafe pointer conversions"`
+	Closure       int    `help:"print information about closure compilation"`
+	CompileLater  int    `help:"compile functions as late as possible"`
+	DclStack      int    `help:"run internal dclstack check"`
+	Defer         int    `help:"print information about defer compilation"`
+	DisableNil    int    `help:"disable nil checks"`
+	DumpPtrs      int    `help:"show Node pointers values in dump output"`
+	DwarfInl      int    `help:"print information about DWARF inlined function creation"`
+	Export        int    `help:"print export data"`
+	Fieldtrack    *int   `help:"enable field tracking"`
+	GCProg        int    `help:"print dump of GC programs"`
+	Libfuzzer     int    `help:"enable coverage instrumentation for libfuzzer"`
+	LocationLists int    `help:"print information about DWARF location list creation"`
+	Nil           int    `help:"print information about nil checks"`
+	PCTab         string `help:"print named pc-value table"`
+	Panic         int    `help:"show all compiler panics"`
+	Slice         int    `help:"print information about slice compilation"`
+	SoftFloat     int    `help:"force compiler to emit soft-float code"`
+	TypeAssert    int    `help:"print information about type assertion inlining"`
+	TypecheckInl  int    `help:"eager typechecking of inline function bodies"`
+	WB            int    `help:"print information about write barriers"`
+
+	any bool // set when any of the values have been set
+}
+
+// Any reports whether any of the debug flags have been set.
+func (d *DebugFlags) Any() bool { return d.any }
+
+type debugField struct {
 	name string
 	help string
-	val  interface{} // must be *int or *string
+	val  interface{} // *int or *string
-}{
-	{"append", "print information about append compilation", &Debug.Append},
-	{"checkptr", "instrument unsafe pointer conversions", &Debug.Checkptr},
-	{"closure", "print information about closure compilation", &Debug.Closure},
-	{"compilelater", "compile functions as late as possible", &Debug.CompileLater},
-	{"disablenil", "disable nil checks", &Debug.DisableNil},
-	{"dclstack", "run internal dclstack check", &Debug.DclStack},
-	{"dumpptrs", "show Node pointer values in Dump/dumplist output", &Debug.DumpPtrs},
-	{"gcprog", "print dump of GC programs", &Debug.GCProg},
-	{"libfuzzer", "coverage instrumentation for libfuzzer", &Debug.Libfuzzer},
-	{"nil", "print information about nil checks", &Debug.Nil},
-	{"panic", "do not hide any compiler panic", &Debug.Panic},
-	{"slice", "print information about slice compilation", &Debug.Slice},
-	{"typeassert", "print information about type assertion inlining", &Debug.TypeAssert},
-	{"wb", "print information about write barriers", &Debug.WB},
-	{"export", "print export data", &Debug.Export},
-	{"pctab", "print named pc-value table", &Debug.PCTab},
-	{"locationlists", "print information about DWARF location list creation", &Debug.LocationLists},
-	{"typecheckinl", "eager typechecking of inline function bodies", &Debug.TypecheckInl},
-	{"dwarfinl", "print information about DWARF inlined function creation", &Debug.DwarfInl},
-	{"softfloat", "force compiler to emit soft-float code", &Debug.SoftFloat},
-	{"defer", "print information about defer compilation", &Debug.Defer},
-	{"fieldtrack", "enable fieldtracking", &objabi.Fieldtrack_enabled},
 }
 
-var Debug struct {
+var debugTab []debugField
-	Append        int
+
-	Checkptr      int
+func init() {
-	Closure       int
+	v := reflect.ValueOf(&Debug).Elem()
-	CompileLater  int
+	t := v.Type()
-	DisableNil    int
+	for i := 0; i < t.NumField(); i++ {
-	DclStack      int
+		f := t.Field(i)
-	GCProg        int
+		if f.Name == "any" {
-	Libfuzzer     int
+			continue
-	Nil           int
+		}
-	Panic         int
+		name := strings.ToLower(f.Name)
-	Slice         int
+		help := f.Tag.Get("help")
-	TypeAssert    int
+		if help == "" {
-	WB            int
+			panic(fmt.Sprintf("base.Debug.%s is missing help text", f.Name))
-	Export        int
+		}
-	PCTab         string
+		ptr := v.Field(i).Addr().Interface()
-	LocationLists int
+		switch ptr.(type) {
-	TypecheckInl  int
+		default:
-	DwarfInl      int
+			panic(fmt.Sprintf("base.Debug.%s has invalid type %v (must be int or string)", f.Name, f.Type))
-	SoftFloat     int
+		case *int, *string:
-	Defer         int
+			// ok
-	DumpPtrs      int
+		case **int:
+			ptr = *ptr.(**int) // record the *int itself
+		}
+		debugTab = append(debugTab, debugField{name, help, ptr})
+	}
 }
 
-func parseDebug() {
+// DebugSSA is called to set a -d ssa/... option.
+// If nil, those options are reported as invalid options.
+// If DebugSSA returns a non-empty string, that text is reported as a compiler error.
+var DebugSSA func(phase, flag string, val int, valString string) string
+
+// parseDebug parses the -d debug string argument.
+func parseDebug(debugstr string) {
 	// parse -d argument
-	if Flag.LowerD != "" {
+	if debugstr == "" {
-	Split:
+		return
-		for _, name := range strings.Split(Flag.LowerD, ",") {
+	}
-			if name == "" {
+	Debug.any = true
+Split:
+	for _, name := range strings.Split(debugstr, ",") {
+		if name == "" {
+			continue
+		}
+		// display help about the -d option itself and quit
+		if name == "help" {
+			fmt.Print(debugHelpHeader)
+			maxLen := len("ssa/help")
+			for _, t := range debugTab {
+				if len(t.name) > maxLen {
+					maxLen = len(t.name)
+				}
+			}
+			for _, t := range debugTab {
+				fmt.Printf("\t%-*s\t%s\n", maxLen, t.name, t.help)
+			}
+			// ssa options have their own help
+			fmt.Printf("\t%-*s\t%s\n", maxLen, "ssa/help", "print help about SSA debugging")
+			fmt.Print(debugHelpFooter)
+			os.Exit(0)
+		}
+		val, valstring, haveInt := 1, "", true
+		if i := strings.IndexAny(name, "=:"); i >= 0 {
+			var err error
+			name, valstring = name[:i], name[i+1:]
+			val, err = strconv.Atoi(valstring)
+			if err != nil {
+				val, haveInt = 1, false
+			}
+		}
+		for _, t := range debugTab {
+			if t.name != name {
 				continue
 			}
-			// display help about the -d option itself and quit
+			switch vp := t.val.(type) {
-			if name == "help" {
+			case nil:
-				fmt.Print(debugHelpHeader)
+				// Ignore
-				maxLen := len("ssa/help")
+			case *string:
-				for _, t := range debugtab {
+				*vp = valstring
-					if len(t.name) > maxLen {
+			case *int:
-						maxLen = len(t.name)
+				if !haveInt {
-					}
+					log.Fatalf("invalid debug value %v", name)
 				}
-				for _, t := range debugtab {
+				*vp = val
-					fmt.Printf("\t%-*s\t%s\n", maxLen, t.name, t.help)
+			default:
-				}
+				panic("bad debugtab type")
-				// ssa options have their own help
-				fmt.Printf("\t%-*s\t%s\n", maxLen, "ssa/help", "print help about SSA debugging")
-				fmt.Print(debugHelpFooter)
-				os.Exit(0)
 			}
-			val, valstring, haveInt := 1, "", true
+			continue Split
-			if i := strings.IndexAny(name, "=:"); i >= 0 {
-				var err error
-				name, valstring = name[:i], name[i+1:]
-				val, err = strconv.Atoi(valstring)
-				if err != nil {
-					val, haveInt = 1, false
-				}
-			}
-			for _, t := range debugtab {
-				if t.name != name {
-					continue
-				}
-				switch vp := t.val.(type) {
-				case nil:
-					// Ignore
-				case *string:
-					*vp = valstring
-				case *int:
-					if !haveInt {
-						log.Fatalf("invalid debug value %v", name)
-					}
-					*vp = val
-				default:
-					panic("bad debugtab type")
-				}
-				continue Split
-			}
-			// special case for ssa for now
-			if strings.HasPrefix(name, "ssa/") {
-				// expect form ssa/phase/flag
-				// e.g. -d=ssa/generic_cse/time
-				// _ in phase name also matches space
-				phase := name[4:]
-				flag := "debug" // default flag is debug
-				if i := strings.Index(phase, "/"); i >= 0 {
-					flag = phase[i+1:]
-					phase = phase[:i]
-				}
-				err := ssa.PhaseOption(phase, flag, val, valstring)
-				if err != "" {
-					log.Fatalf(err)
-				}
-				continue Split
-			}
-			log.Fatalf("unknown debug key -d %s\n", name)
 		}
+		// special case for ssa for now
+		if DebugSSA != nil && strings.HasPrefix(name, "ssa/") {
+			// expect form ssa/phase/flag
+			// e.g. -d=ssa/generic_cse/time
+			// _ in phase name also matches space
+			phase := name[4:]
+			flag := "debug" // default flag is debug
+			if i := strings.Index(phase, "/"); i >= 0 {
+				flag = phase[i+1:]
+				phase = phase[:i]
+			}
+			err := DebugSSA(phase, flag, val, valstring)
+			if err != "" {
+				log.Fatalf(err)
+			}
+			continue Split
+		}
+		log.Fatalf("unknown debug key -d %s\n", name)
 	}
 }
 

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

@@ -63,19 +63,19 @@ type CmdFlags struct {
 	// V is added by objabi.AddVersionFlag
 	W CountFlag "help:\"debug parse tree after type checking\""
 
-	LowerC int       "help:\"concurrency during compilation (1 means no concurrency)\""
+	LowerC int          "help:\"concurrency during compilation (1 means no concurrency)\""
-	LowerD string    "help:\"enable debugging settings; try -d help\""
+	LowerD func(string) "help:\"enable debugging settings; try -d help\""
-	LowerE CountFlag "help:\"no limit on number of errors reported\""
+	LowerE CountFlag    "help:\"no limit on number of errors reported\""
-	LowerH CountFlag "help:\"halt on error\""
+	LowerH CountFlag    "help:\"halt on error\""
-	LowerJ CountFlag "help:\"debug runtime-initialized variables\""
+	LowerJ CountFlag    "help:\"debug runtime-initialized variables\""
-	LowerL CountFlag "help:\"disable inlining\""
+	LowerL CountFlag    "help:\"disable inlining\""
-	LowerM CountFlag "help:\"print optimization decisions\""
+	LowerM CountFlag    "help:\"print optimization decisions\""
-	LowerO string    "help:\"write output to `file`\""
+	LowerO string       "help:\"write output to `file`\""
-	LowerP *string   "help:\"set expected package import `path`\"" // &Ctxt.Pkgpath, set below
+	LowerP *string      "help:\"set expected package import `path`\"" // &Ctxt.Pkgpath, set below
-	LowerR CountFlag "help:\"debug generated wrappers\""
+	LowerR CountFlag    "help:\"debug generated wrappers\""
-	LowerT bool      "help:\"enable tracing for debugging the compiler\""
+	LowerT bool         "help:\"enable tracing for debugging the compiler\""
-	LowerW CountFlag "help:\"debug type checking\""
+	LowerW CountFlag    "help:\"debug type checking\""
-	LowerV *bool     "help:\"increase debug verbosity\""
+	LowerV *bool        "help:\"increase debug verbosity\""
 
 	// Special characters
 	Percent          int  "flag:\"%\" help:\"debug non-static initializers\""
@@ -137,6 +137,7 @@ func ParseFlags() {
 	Flag.I = addImportDir
 
 	Flag.LowerC = 1
+	Flag.LowerD = parseDebug
 	Flag.LowerP = &Ctxt.Pkgpath
 	Flag.LowerV = &Ctxt.Debugvlog
 
@@ -174,7 +175,7 @@ func ParseFlags() {
 	Ctxt.Flag_optimize = Flag.N == 0
 	Ctxt.Debugasm = int(Flag.S)
 
-	if flag.NArg() < 1 && Flag.LowerD != "help" && Flag.LowerD != "ssa/help" {
+	if flag.NArg() < 1 {
 		usage()
 	}
 
@@ -221,8 +222,6 @@ func ParseFlags() {
 		log.Fatalf("cannot use concurrent backend compilation with provided flags; invoked as %v", os.Args)
 	}
 
-	parseDebug()
-
 	if Flag.CompilingRuntime {
 		// Runtime can't use -d=checkptr, at least not yet.
 		Debug.Checkptr = 0
@@ -330,7 +329,7 @@ func concurrentBackendAllowed() bool {
 	// while writing the object file, and that is non-concurrent.
 	// Adding Debug_vlog, however, causes Debug.S to also print
 	// while flushing the plist, which happens concurrently.
-	if Ctxt.Debugvlog || Flag.LowerD != "" || Flag.Live > 0 {
+	if Ctxt.Debugvlog || Debug.Any() || Flag.Live > 0 {
 		return false
 	}
 	// TODO: Test and delete this condition.

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

@@ -10,7 +10,7 @@ import (
 	"bufio"
 	"bytes"
 	"cmd/compile/internal/logopt"
-
+	"cmd/compile/internal/ssa"
 	"cmd/compile/internal/types"
 	"cmd/internal/bio"
 	"cmd/internal/dwarf"
@@ -112,6 +112,7 @@ func Main(archInit func(*Arch)) {
 	// pseudo-package used for methods with anonymous receivers
 	gopkg = types.NewPkg("go", "")
 
+	DebugSSA = ssa.PhaseOption
 	ParseFlags()
 
 	// Record flags that affect the build result. (And don't