cmd/compile: remove -wrapglobalmapinit flag

Remove the compiler's "-wrapglobalmapinit" flag; it is potentially
confusing for users and isn't appropriate as a top level flag. Move
the enable/disable control to the "wrapglobalmapctl" debug flag
(values: 0 on by default, 1 disabled, 2 stress mode). No other changes
to compiler functionality.

Change-Id: I0d120eaf90ee34e29d5032889e673d42fe99e5dc
Reviewed-on: https://go-review.googlesource.com/c/go/+/475035
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

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

@@ -50,11 +50,11 @@ type DebugFlags struct {
 	WB                    int    `help:"print information about write barriers"`
 	ABIWrap               int    `help:"print information about ABI wrapper generation"`
 	MayMoreStack          string `help:"call named function before all stack growth checks" concurrent:"ok"`
-	PGOInlineCDFThreshold string `help:"cummulative threshold percentage for determining call sites as hot candidates for inlining" concurrent:"ok"`
+	PGOInlineCDFThreshold string `help:"cumulative threshold percentage for determining call sites as hot candidates for inlining" concurrent:"ok"`
 	PGOInlineBudget       int    `help:"inline budget for hot functions" concurrent:"ok"`
 	PGOInline             int    `help:"debug profile-guided inlining"`
-	WrapGlobalMapDbg      int    "help:\"debug trace output for global map init wrapping\""
+	WrapGlobalMapDbg      int    `help:"debug trace output for global map init wrapping"`
-	WrapGlobalMapStress   int    "help:\"run global map init wrap in stress mode (no size cutoff)\""
+	WrapGlobalMapCtl      int    `help:"global map init wrap control (0 => default, 1 => off, 2 => stress mode, no size cutoff)"`
 
 	ConcurrentOk bool // true if only concurrentOk flags seen
 }

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

@@ -123,7 +123,6 @@ type CmdFlags struct {
 	TraceProfile       string       "help:\"write an execution trace to `file`\""
 	TrimPath           string       "help:\"remove `prefix` from recorded source file paths\""
 	WB                 bool         "help:\"enable write barrier\"" // TODO: remove
-	WrapGlobalMapInit  bool         "help:\"wrap global map large inits in their own functions (to permit deadcode)\""
 	PgoProfile         string       "help:\"read profile from `file`\""
 
 	// Configuration derived from flags; not a flag itself.
@@ -164,7 +163,6 @@ func ParseFlags() {
 	Flag.LinkShared = &Ctxt.Flag_linkshared
 	Flag.Shared = &Ctxt.Flag_shared
 	Flag.WB = true
-	Flag.WrapGlobalMapInit = true
 
 	Debug.ConcurrentOk = true
 	Debug.InlFuncsWithClosures = 1

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

@@ -374,7 +374,7 @@ func Main(archInit func(*ssagen.ArchInfo)) {
 	}
 
 	// Add keep relocations for global maps.
-	if base.Flag.WrapGlobalMapInit {
+	if base.Debug.WrapGlobalMapCtl != 1 {
 		staticinit.AddKeepRelocations()
 	}
 

src/cmd/compile/internal/ssagen/pgen.go

@@ -214,7 +214,7 @@ func Compile(fn *ir.Func, worker int) {
 	// If we're compiling the package init function, search for any
 	// relocations that target global map init outline functions and
 	// turn them into weak relocs.
-	if base.Flag.WrapGlobalMapInit && fn.IsPackageInit() {
+	if fn.IsPackageInit() && base.Debug.WrapGlobalMapCtl != 1 {
 		weakenGlobalMapInitRelocs(fn)
 	}
 

src/cmd/compile/internal/staticinit/sched.go

@@ -945,7 +945,7 @@ func tryWrapGlobalMapInit(n ir.Node) (mapvar *ir.Name, genfn *ir.Func, call ir.N
 	}
 
 	// Reject smaller candidates if not in stress mode.
-	if rsiz < wrapGlobalMapInitSizeThreshold && base.Debug.WrapGlobalMapStress == 0 {
+	if rsiz < wrapGlobalMapInitSizeThreshold && base.Debug.WrapGlobalMapCtl != 2 {
 		if base.Debug.WrapGlobalMapDbg > 1 {
 			fmt.Fprintf(os.Stderr, "=-= skipping %v size too small at %d\n",
 				nm, rsiz)
@@ -1046,7 +1046,7 @@ func AddKeepRelocations() {
 // functions (if legal/profitable). Return value is an updated list
 // and a list of any newly generated "map init" functions.
 func OutlineMapInits(stmts []ir.Node) ([]ir.Node, []*ir.Func) {
-	if !base.Flag.WrapGlobalMapInit {
+	if base.Debug.WrapGlobalMapCtl == 1 {
 		return stmts, nil
 	}
 	newfuncs := []*ir.Func{}