[dev.regabi] cmd/compile: separate various from Main

Move various code out of Main itself and into helper functions
that can be moved into other packages as package gc splits up.

Similarly, move order and instrument inside walk to reduce the amount
of API surface needed from the eventual package walk.

Change-Id: I7849258038c6e39625a0385af9c0edd6a3b654a1
Reviewed-on: https://go-review.googlesource.com/c/go/+/279304
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -36,7 +36,13 @@ func TestMain(m *testing.M) {
 	base.Ctxt.Bso = bufio.NewWriter(os.Stdout)
 	Widthptr = thearch.LinkArch.PtrSize
 	Widthreg = thearch.LinkArch.RegSize
-	initializeTypesPackage()
+	types.TypeLinkSym = func(t *types.Type) *obj.LSym {
+		return typenamesym(t).Linksym()
+	}
+	types.TypeLinkSym = func(t *types.Type) *obj.LSym {
+		return typenamesym(t).Linksym()
+	}
+	TypecheckInit()
 	os.Exit(m.Run())
 }
 

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

@@ -442,6 +442,12 @@ type funcStackEnt struct {
 	dclcontext ir.Class
 }
 
+func CheckFuncStack() {
+	if len(funcStack) != 0 {
+		base.Fatalf("funcStack is non-empty: %v", len(funcStack))
+	}
+}
+
 // finish the body.
 // called in auto-declaration context.
 // returns in extern-declaration context.

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

@@ -129,8 +129,6 @@ var (
 	iscmp [ir.OEND]bool
 )
 
-var importlist []*ir.Func // imported functions and methods with inlinable bodies
-
 var (
 	funcsymsmu sync.Mutex // protects funcsyms and associated package lookups (see func funcsym)
 	funcsyms   []*types.Sym

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

@@ -55,6 +55,26 @@ const (
 	inlineBigFunctionMaxCost = 20   // Max cost of inlinee when inlining into a "big" function.
 )
 
+func InlinePackage() {
+	// Find functions that can be inlined and clone them before walk expands them.
+	visitBottomUp(Target.Decls, func(list []*ir.Func, recursive bool) {
+		numfns := numNonClosures(list)
+		for _, n := range list {
+			if !recursive || numfns > 1 {
+				// We allow inlining if there is no
+				// recursion, or the recursion cycle is
+				// across more than one function.
+				caninl(n)
+			} else {
+				if base.Flag.LowerM > 1 {
+					fmt.Printf("%v: cannot inline %v: recursive\n", ir.Line(n), n.Nname)
+				}
+			}
+			inlcalls(n)
+		}
+	})
+}
+
 // Get the function's package. For ordinary functions it's on the ->sym, but for imported methods
 // the ->sym can be re-used in the local package, so peel it off the receiver's type.
 func fnpkg(fn *ir.Name) *types.Pkg {

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

@@ -191,24 +191,15 @@ func Main(archInit func(*Arch)) {
 
 	IsIntrinsicCall = isIntrinsicCall
 	SSADumpInline = ssaDumpInline
-
-	ssaDump = os.Getenv("GOSSAFUNC")
-	ssaDir = os.Getenv("GOSSADIR")
-	if ssaDump != "" {
-		if strings.HasSuffix(ssaDump, "+") {
-			ssaDump = ssaDump[:len(ssaDump)-1]
-			ssaDumpStdout = true
-		}
-		spl := strings.Split(ssaDump, ":")
-		if len(spl) > 1 {
-			ssaDump = spl[0]
-			ssaDumpCFG = spl[1]
-		}
-	}
+	initSSAEnv()
+	initSSATables()
 
 	Widthptr = thearch.LinkArch.PtrSize
 	Widthreg = thearch.LinkArch.RegSize
 	MaxWidth = thearch.MAXWIDTH
+	types.TypeLinkSym = func(t *types.Type) *obj.LSym {
+		return typenamesym(t).Linksym()
+	}
 
 	Target = new(ir.Package)
 
@@ -216,152 +207,40 @@ func Main(archInit func(*Arch)) {
 	NeedITab = func(t, iface *types.Type) { itabname(t, iface) }
 	NeedRuntimeType = addsignat // TODO(rsc): typenamesym for lock?
 
-	// initialize types package
-	// (we need to do this to break dependencies that otherwise
-	// would lead to import cycles)
-	initializeTypesPackage()
-
-	dclcontext = ir.PEXTERN
-
 	autogeneratedPos = makePos(src.NewFileBase("<autogenerated>", "<autogenerated>"), 1, 0)
 
-	timings.Start("fe", "loadsys")
-	loadsys()
+	types.TypeLinkSym = func(t *types.Type) *obj.LSym {
+		return typenamesym(t).Linksym()
+	}
+	TypecheckInit()
 
+	// Parse input.
 	timings.Start("fe", "parse")
 	lines := parseFiles(flag.Args())
 	cgoSymABIs()
 	timings.Stop()
 	timings.AddEvent(int64(lines), "lines")
-
-	finishUniverse()
-
 	recordPackageName()
 
-	typecheckok = true
+	// Typecheck.
+	TypecheckPackage()
 
-	// Process top-level declarations in phases.
-
-	// Phase 1: const, type, and names and types of funcs.
-	//   This will gather all the information about types
-	//   and methods but doesn't depend on any of it.
-	//
-	//   We also defer type alias declarations until phase 2
-	//   to avoid cycles like #18640.
-	//   TODO(gri) Remove this again once we have a fix for #25838.
-
-	// Don't use range--typecheck can add closures to Target.Decls.
-	timings.Start("fe", "typecheck", "top1")
-	for i := 0; i < len(Target.Decls); i++ {
-		n := Target.Decls[i]
-		if op := n.Op(); op != ir.ODCL && op != ir.OAS && op != ir.OAS2 && (op != ir.ODCLTYPE || !n.(*ir.Decl).Left().Name().Alias()) {
-			Target.Decls[i] = typecheck(n, ctxStmt)
-		}
-	}
-
-	// Phase 2: Variable assignments.
-	//   To check interface assignments, depends on phase 1.
-
-	// Don't use range--typecheck can add closures to Target.Decls.
-	timings.Start("fe", "typecheck", "top2")
-	for i := 0; i < len(Target.Decls); i++ {
-		n := Target.Decls[i]
-		if op := n.Op(); op == ir.ODCL || op == ir.OAS || op == ir.OAS2 || op == ir.ODCLTYPE && n.(*ir.Decl).Left().Name().Alias() {
-			Target.Decls[i] = typecheck(n, ctxStmt)
-		}
-	}
-
-	// Phase 3: Type check function bodies.
-	// Don't use range--typecheck can add closures to Target.Decls.
-	timings.Start("fe", "typecheck", "func")
-	var fcount int64
-	for i := 0; i < len(Target.Decls); i++ {
-		n := Target.Decls[i]
-		if n.Op() == ir.ODCLFUNC {
-			Curfn = n.(*ir.Func)
-			decldepth = 1
-			errorsBefore := base.Errors()
-			typecheckslice(Curfn.Body().Slice(), ctxStmt)
-			checkreturn(Curfn)
-			if base.Errors() > errorsBefore {
-				Curfn.PtrBody().Set(nil) // type errors; do not compile
-			}
-			// Now that we've checked whether n terminates,
-			// we can eliminate some obviously dead code.
-			deadcode(Curfn)
-			fcount++
-		}
-	}
-
-	// Phase 3.11: Check external declarations.
-	// TODO(mdempsky): This should be handled when type checking their
-	// corresponding ODCL nodes.
-	timings.Start("fe", "typecheck", "externdcls")
-	for i, n := range Target.Externs {
-		if n.Op() == ir.ONAME {
-			Target.Externs[i] = typecheck(Target.Externs[i], ctxExpr)
-		}
-	}
-
-	// Phase 3.14: With all user code type-checked, it's now safe to verify map keys
-	// and unused dot imports.
-	checkMapKeys()
+	// With all user code typechecked, it's now safe to verify unused dot imports.
 	checkDotImports()
 	base.ExitIfErrors()
 
-	timings.AddEvent(fcount, "funcs")
-
+	// Build init task.
 	if initTask := fninit(); initTask != nil {
 		exportsym(initTask)
 	}
 
-	// Phase 4: Decide how to capture closed variables.
-	// This needs to run before escape analysis,
-	// because variables captured by value do not escape.
-	timings.Start("fe", "capturevars")
-	for _, n := range Target.Decls {
-		if n.Op() == ir.ODCLFUNC && n.Func().OClosure != nil {
-			Curfn = n.(*ir.Func)
-			capturevars(Curfn)
-		}
-	}
-	capturevarscomplete = true
-	Curfn = nil
-	base.ExitIfErrors()
-
-	// Phase 5: Inlining
+	// Inlining
 	timings.Start("fe", "inlining")
-	if base.Debug.TypecheckInl != 0 {
-		// Typecheck imported function bodies if Debug.l > 1,
-		// otherwise lazily when used or re-exported.
-		for _, n := range importlist {
-			if n.Inl != nil {
-				typecheckinl(n)
-			}
-		}
-		base.ExitIfErrors()
-	}
-
 	if base.Flag.LowerL != 0 {
-		// Find functions that can be inlined and clone them before walk expands them.
-		visitBottomUp(Target.Decls, func(list []*ir.Func, recursive bool) {
-			numfns := numNonClosures(list)
-			for _, n := range list {
-				if !recursive || numfns > 1 {
-					// We allow inlining if there is no
-					// recursion, or the recursion cycle is
-					// across more than one function.
-					caninl(n)
-				} else {
-					if base.Flag.LowerM > 1 {
-						fmt.Printf("%v: cannot inline %v: recursive\n", ir.Line(n), n.Nname)
-					}
-				}
-				inlcalls(n)
-			}
-		})
+		InlinePackage()
 	}
 
+	// Devirtualize.
 	for _, n := range Target.Decls {
 		if n.Op() == ir.ODCLFUNC {
 			devirtualize(n.(*ir.Func))
@@ -369,7 +248,7 @@ func Main(archInit func(*Arch)) {
 	}
 	Curfn = nil
 
-	// Phase 6: Escape analysis.
+	// Escape analysis.
 	// Required for moving heap allocations onto stack,
 	// which in turn is required by the closure implementation,
 	// which stores the addresses of stack variables into the closure.
@@ -388,7 +267,7 @@ func Main(archInit func(*Arch)) {
 		EnableNoWriteBarrierRecCheck()
 	}
 
-	// Phase 7: Transform closure bodies to properly reference captured variables.
+	// Transform closure bodies to properly reference captured variables.
 	// This needs to happen before walk, because closures must be transformed
 	// before walk reaches a call of a closure.
 	timings.Start("fe", "xclosures")
@@ -410,10 +289,10 @@ func Main(archInit func(*Arch)) {
 	Curfn = nil
 	peekitabs()
 
-	// Phase 8: Compile top level functions.
+	// Compile top level functions.
 	// Don't use range--walk can add functions to Target.Decls.
 	timings.Start("be", "compilefuncs")
-	fcount = 0
+	fcount := int64(0)
 	for i := 0; i < len(Target.Decls); i++ {
 		n := Target.Decls[i]
 		if n.Op() == ir.ODCLFUNC {
@@ -448,21 +327,9 @@ func Main(archInit func(*Arch)) {
 		dumpasmhdr()
 	}
 
-	// Check whether any of the functions we have compiled have gigantic stack frames.
-	sort.Slice(largeStackFrames, func(i, j int) bool {
-		return largeStackFrames[i].pos.Before(largeStackFrames[j].pos)
-	})
-	for _, large := range largeStackFrames {
-		if large.callee != 0 {
-			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args + %d MB callee", large.locals>>20, large.args>>20, large.callee>>20)
-		} else {
-			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args", large.locals>>20, large.args>>20)
-		}
-	}
+	CheckLargeStacks()
+	CheckFuncStack()
 
-	if len(funcStack) != 0 {
-		base.Fatalf("funcStack is non-empty: %v", len(funcStack))
-	}
 	if len(compilequeue) != 0 {
 		base.Fatalf("%d uncompiled functions", len(compilequeue))
 	}
@@ -480,6 +347,20 @@ func Main(archInit func(*Arch)) {
 	}
 }
 
+func CheckLargeStacks() {
+	// Check whether any of the functions we have compiled have gigantic stack frames.
+	sort.Slice(largeStackFrames, func(i, j int) bool {
+		return largeStackFrames[i].pos.Before(largeStackFrames[j].pos)
+	})
+	for _, large := range largeStackFrames {
+		if large.callee != 0 {
+			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args + %d MB callee", large.locals>>20, large.args>>20, large.callee>>20)
+		} else {
+			base.ErrorfAt(large.pos, "stack frame too large (>1GB): %d MB locals + %d MB args", large.locals>>20, large.args>>20)
+		}
+	}
+}
+
 func cgoSymABIs() {
 	// The linker expects an ABI0 wrapper for all cgo-exported
 	// functions.
@@ -1140,16 +1021,6 @@ func parseLang(s string) (lang, error) {
 	return lang{major: major, minor: minor}, nil
 }
 
-func initializeTypesPackage() {
-	types.Widthptr = Widthptr
-	types.Dowidth = dowidth
-	types.TypeLinkSym = func(t *types.Type) *obj.LSym {
-		return typenamesym(t).Linksym()
-	}
-
-	initUniverse()
-}
-
 // useNewABIWrapGen returns TRUE if the compiler should generate an
 // ABI wrapper for the function 'f'.
 func useABIWrapGen(f *ir.Func) bool {

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

@@ -222,24 +222,16 @@ func funccompile(fn *ir.Func) {
 }
 
 func compile(fn *ir.Func) {
-	errorsBefore := base.Errors()
-	order(fn)
-	if base.Errors() > errorsBefore {
-		return
-	}
-
 	// Set up the function's LSym early to avoid data races with the assemblers.
 	// Do this before walk, as walk needs the LSym to set attributes/relocations
 	// (e.g. in markTypeUsedInInterface).
 	initLSym(fn, true)
 
+	errorsBefore := base.Errors()
 	walk(fn)
 	if base.Errors() > errorsBefore {
 		return
 	}
-	if instrumenting {
-		instrument(fn)
-	}
 
 	// From this point, there should be no uses of Curfn. Enforce that.
 	Curfn = nil

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

@@ -12,6 +12,7 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
+	"strings"
 
 	"bufio"
 	"bytes"
@@ -48,6 +49,22 @@ func ssaDumpInline(fn *ir.Func) {
 	}
 }
 
+func initSSAEnv() {
+	ssaDump = os.Getenv("GOSSAFUNC")
+	ssaDir = os.Getenv("GOSSADIR")
+	if ssaDump != "" {
+		if strings.HasSuffix(ssaDump, "+") {
+			ssaDump = ssaDump[:len(ssaDump)-1]
+			ssaDumpStdout = true
+		}
+		spl := strings.Split(ssaDump, ":")
+		if len(spl) > 1 {
+			ssaDump = spl[0]
+			ssaDumpCFG = spl[1]
+		}
+	}
+}
+
 func initssaconfig() {
 	types_ := ssa.NewTypes()
 
@@ -3357,7 +3374,7 @@ type intrinsicKey struct {
 	fn   string
 }
 
-func init() {
+func initSSATables() {
 	intrinsics = map[intrinsicKey]intrinsicBuilder{}
 
 	var all []*sys.Arch

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

@@ -20,6 +20,96 @@ var (
 	NeedRuntimeType = func(*types.Type) {}
 )
 
+func TypecheckInit() {
+	types.Widthptr = Widthptr
+	types.Dowidth = dowidth
+	initUniverse()
+	dclcontext = ir.PEXTERN
+	timings.Start("fe", "loadsys")
+	loadsys()
+}
+
+func TypecheckPackage() {
+	finishUniverse()
+
+	typecheckok = true
+
+	// Process top-level declarations in phases.
+
+	// Phase 1: const, type, and names and types of funcs.
+	//   This will gather all the information about types
+	//   and methods but doesn't depend on any of it.
+	//
+	//   We also defer type alias declarations until phase 2
+	//   to avoid cycles like #18640.
+	//   TODO(gri) Remove this again once we have a fix for #25838.
+
+	// Don't use range--typecheck can add closures to Target.Decls.
+	timings.Start("fe", "typecheck", "top1")
+	for i := 0; i < len(Target.Decls); i++ {
+		n := Target.Decls[i]
+		if op := n.Op(); op != ir.ODCL && op != ir.OAS && op != ir.OAS2 && (op != ir.ODCLTYPE || !n.(*ir.Decl).Left().Name().Alias()) {
+			Target.Decls[i] = typecheck(n, ctxStmt)
+		}
+	}
+
+	// Phase 2: Variable assignments.
+	//   To check interface assignments, depends on phase 1.
+
+	// Don't use range--typecheck can add closures to Target.Decls.
+	timings.Start("fe", "typecheck", "top2")
+	for i := 0; i < len(Target.Decls); i++ {
+		n := Target.Decls[i]
+		if op := n.Op(); op == ir.ODCL || op == ir.OAS || op == ir.OAS2 || op == ir.ODCLTYPE && n.(*ir.Decl).Left().Name().Alias() {
+			Target.Decls[i] = typecheck(n, ctxStmt)
+		}
+	}
+
+	// Phase 3: Type check function bodies.
+	// Don't use range--typecheck can add closures to Target.Decls.
+	timings.Start("fe", "typecheck", "func")
+	var fcount int64
+	for i := 0; i < len(Target.Decls); i++ {
+		n := Target.Decls[i]
+		if n.Op() == ir.ODCLFUNC {
+			TypecheckFuncBody(n.(*ir.Func))
+			fcount++
+		}
+	}
+
+	// Phase 4: Check external declarations.
+	// TODO(mdempsky): This should be handled when type checking their
+	// corresponding ODCL nodes.
+	timings.Start("fe", "typecheck", "externdcls")
+	for i, n := range Target.Externs {
+		if n.Op() == ir.ONAME {
+			Target.Externs[i] = typecheck(Target.Externs[i], ctxExpr)
+		}
+	}
+
+	// Phase 5: With all user code type-checked, it's now safe to verify map keys.
+	checkMapKeys()
+
+	// Phase 6: Decide how to capture closed variables.
+	// This needs to run before escape analysis,
+	// because variables captured by value do not escape.
+	timings.Start("fe", "capturevars")
+	for _, n := range Target.Decls {
+		if n.Op() == ir.ODCLFUNC && n.Func().OClosure != nil {
+			Curfn = n.(*ir.Func)
+			capturevars(Curfn)
+		}
+	}
+	capturevarscomplete = true
+	Curfn = nil
+
+	if base.Debug.TypecheckInl != 0 {
+		// Typecheck imported function bodies if Debug.l > 1,
+		// otherwise lazily when used or re-exported.
+		TypecheckImports()
+	}
+}
+
 func TypecheckAssignExpr(n ir.Node) ir.Node { return typecheck(n, ctxExpr|ctxAssign) }
 func TypecheckExpr(n ir.Node) ir.Node       { return typecheck(n, ctxExpr) }
 func TypecheckStmt(n ir.Node) ir.Node       { return typecheck(n, ctxStmt) }
@@ -45,6 +135,30 @@ func TypecheckCallee(n ir.Node) ir.Node {
 	return typecheck(n, ctxExpr|ctxCallee)
 }
 
+func TypecheckFuncBody(n *ir.Func) {
+	Curfn = n
+	decldepth = 1
+	errorsBefore := base.Errors()
+	typecheckslice(n.Body(), ctxStmt)
+	checkreturn(n)
+	if base.Errors() > errorsBefore {
+		n.PtrBody().Set(nil) // type errors; do not compile
+	}
+	// Now that we've checked whether n terminates,
+	// we can eliminate some obviously dead code.
+	deadcode(n)
+}
+
+var importlist []*ir.Func
+
+func TypecheckImports() {
+	for _, n := range importlist {
+		if n.Inl != nil {
+			typecheckinl(n)
+		}
+	}
+}
+
 // To enable tracing support (-t flag), set enableTrace to true.
 const enableTrace = false
 

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

@@ -26,6 +26,10 @@ const zeroValSize = 1024 // must match value of runtime/map.go:maxZero
 func walk(fn *ir.Func) {
 	Curfn = fn
 	errorsBefore := base.Errors()
+	order(fn)
+	if base.Errors() > errorsBefore {
+		return
+	}
 
 	if base.Flag.W != 0 {
 		s := fmt.Sprintf("\nbefore walk %v", Curfn.Sym())
@@ -80,6 +84,10 @@ func walk(fn *ir.Func) {
 		s := fmt.Sprintf("enter %v", Curfn.Sym())
 		ir.DumpList(s, Curfn.Enter)
 	}
+
+	if instrumenting {
+		instrument(fn)
+	}
 }
 
 func walkstmtlist(s []ir.Node) {