[dev.regabi] cmd/compile: cleanup for concrete types - import/export

An automated rewrite will add concrete type assertions after
a test of n.Op(), when n can be safely type-asserted
(meaning, n is not reassigned a different type, n is not reassigned
and then used outside the scope of the type assertion,
and so on).

This sequence of CLs handles the code that the automated
rewrite does not: adding specific types to function arguments,
adjusting code not to call n.Left() etc when n may have multiple
representations, and so on.

This CL focuses on iimport.go and iexport.go.

Passes buildall w/ toolstash -cmp.

Change-Id: I63edee54991ae5d982e99efa7a2894478d511910
Reviewed-on: https://go-review.googlesource.com/c/go/+/277925
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -15,8 +15,11 @@ type exporter struct {
 
 // markObject visits a reachable object.
 func (p *exporter) markObject(n ir.Node) {
-	if n.Op() == ir.ONAME && n.Class() == ir.PFUNC {
+	if n.Op() == ir.ONAME {
-		inlFlood(n.(*ir.Name))
+		n := n.(*ir.Name)
+		if n.Class() == ir.PFUNC {
+			inlFlood(n)
+		}
 	}
 
 	p.markType(n.Type())

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

@@ -1,20 +0,0 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package gc
-
-import (
-	"cmd/compile/internal/ir"
-	"cmd/compile/internal/types"
-	"cmd/internal/src"
-)
-
-func npos(pos src.XPos, n ir.Node) ir.Node {
-	n.SetPos(pos)
-	return n
-}
-
-func builtinCall(op ir.Op) ir.Node {
-	return ir.Nod(ir.OCALL, mkname(types.BuiltinPkg.Lookup(ir.OpNames[op])), nil)
-}

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

@@ -1069,7 +1069,7 @@ func (w *exportWriter) stmt(n ir.Node) {
 		}
 	}
 
-	switch op := n.Op(); op {
+	switch n.Op() {
 	case ir.OBLOCK:
 		// No OBLOCK in export data.
 		// Inline content into this statement list,
@@ -1084,7 +1084,7 @@ func (w *exportWriter) stmt(n ir.Node) {
 	case ir.ODCL:
 		w.op(ir.ODCL)
 		w.pos(n.Left().Pos())
-		w.localName(n.Left())
+		w.localName(n.Left().(*ir.Name))
 		w.typ(n.Left().Type())
 
 	case ir.OAS:
@@ -1099,9 +1099,10 @@ func (w *exportWriter) stmt(n ir.Node) {
 		}
 
 	case ir.OASOP:
+		n := n.(*ir.AssignOpStmt)
 		w.op(ir.OASOP)
 		w.pos(n.Pos())
-		w.op(n.SubOp())
+		w.op(n.AsOp)
 		w.expr(n.Left())
 		if w.bool(!n.Implicit()) {
 			w.expr(n.Right())
@@ -1122,7 +1123,7 @@ func (w *exportWriter) stmt(n ir.Node) {
 	// 	unreachable - generated by compiler for trampolin routines
 
 	case ir.OGO, ir.ODEFER:
-		w.op(op)
+		w.op(n.Op())
 		w.pos(n.Pos())
 		w.expr(n.Left())
 
@@ -1148,8 +1149,15 @@ func (w *exportWriter) stmt(n ir.Node) {
 		w.expr(n.Right())
 		w.stmtList(n.Body())
 
-	case ir.OSELECT, ir.OSWITCH:
+	case ir.OSELECT:
-		w.op(op)
+		w.op(n.Op())
+		w.pos(n.Pos())
+		w.stmtList(n.Init())
+		w.exprsOrNil(nil, nil) // TODO(rsc): Delete (and fix importer).
+		w.caseList(n)
+
+	case ir.OSWITCH:
+		w.op(n.Op())
 		w.pos(n.Pos())
 		w.stmtList(n.Init())
 		w.exprsOrNil(n.Left(), nil)
@@ -1163,7 +1171,7 @@ func (w *exportWriter) stmt(n ir.Node) {
 		w.pos(n.Pos())
 
 	case ir.OBREAK, ir.OCONTINUE, ir.OGOTO, ir.OLABEL:
-		w.op(op)
+		w.op(n.Op())
 		w.pos(n.Pos())
 		label := ""
 		if sym := n.Sym(); sym != nil {
@@ -1176,19 +1184,34 @@ func (w *exportWriter) stmt(n ir.Node) {
 	}
 }
 
-func (w *exportWriter) caseList(sw ir.Node) {
+func isNamedTypeSwitch(n ir.Node) bool {
-	namedTypeSwitch := sw.Op() == ir.OSWITCH && sw.Left() != nil && sw.Left().Op() == ir.OTYPESW && sw.Left().Left() != nil
+	if n.Op() != ir.OSWITCH {
+		return false
+	}
+	sw := n.(*ir.SwitchStmt)
+	if sw.Left() == nil || sw.Left().Op() != ir.OTYPESW {
+		return false
+	}
+	guard := sw.Left().(*ir.TypeSwitchGuard)
+	return guard.Left() != nil
+}
 
-	cases := sw.List().Slice()
+func (w *exportWriter) caseList(sw ir.Node) {
+	namedTypeSwitch := isNamedTypeSwitch(sw)
+
+	var cases []ir.Node
+	if sw.Op() == ir.OSWITCH {
+		cases = sw.(*ir.SwitchStmt).List().Slice()
+	} else {
+		cases = sw.(*ir.SelectStmt).List().Slice()
+	}
 	w.uint64(uint64(len(cases)))
 	for _, cas := range cases {
-		if cas.Op() != ir.OCASE {
+		cas := cas.(*ir.CaseStmt)
-			base.Fatalf("expected OCASE, got %v", cas)
-		}
 		w.pos(cas.Pos())
 		w.stmtList(cas.List())
 		if namedTypeSwitch {
-			w.localName(cas.Rlist().First())
+			w.localName(cas.Rlist().First().(*ir.Name))
 		}
 		w.stmtList(cas.Body())
 	}
@@ -1201,22 +1224,29 @@ func (w *exportWriter) exprList(list ir.Nodes) {
 	w.op(ir.OEND)
 }
 
-func (w *exportWriter) expr(n ir.Node) {
+func simplifyForExport(n ir.Node) ir.Node {
-	// from nodefmt (fmt.go)
+	switch n.Op() {
-	//
+	case ir.OPAREN:
-	// nodefmt reverts nodes back to their original - we don't need to do
+		return simplifyForExport(n.Left())
-	// it because we are not bound to produce valid Go syntax when exporting
+	case ir.ODEREF:
-	//
+		if n.Implicit() {
-	// if (fmtmode != FExp || n.Op != OLITERAL) && n.Orig != nil {
+			return simplifyForExport(n.Left())
-	// 	n = n.Orig
+		}
-	// }
+	case ir.OADDR:
-
+		if n.Implicit() {
-	// from exprfmt (fmt.go)
+			return simplifyForExport(n.Left())
-	for n.Op() == ir.OPAREN || n.Implicit() && (n.Op() == ir.ODEREF || n.Op() == ir.OADDR || n.Op() == ir.ODOT || n.Op() == ir.ODOTPTR) {
+		}
-		n = n.Left()
+	case ir.ODOT, ir.ODOTPTR:
+		if n.Implicit() {
+			return simplifyForExport(n.Left())
+		}
 	}
+	return n
+}
 
-	switch op := n.Op(); op {
+func (w *exportWriter) expr(n ir.Node) {
+	n = simplifyForExport(n)
+	switch n.Op() {
 	// expressions
 	// (somewhat closely following the structure of exprfmt in fmt.go)
 	case ir.ONIL:
@@ -1243,6 +1273,7 @@ func (w *exportWriter) expr(n ir.Node) {
 
 	case ir.ONAME:
 		// Package scope name.
+		n := n.(*ir.Name)
 		if (n.Class() == ir.PEXTERN || n.Class() == ir.PFUNC) && !ir.IsBlank(n) {
 			w.op(ir.ONONAME)
 			w.qualifiedIdent(n)
@@ -1291,7 +1322,7 @@ func (w *exportWriter) expr(n ir.Node) {
 		w.op(ir.OSTRUCTLIT)
 		w.pos(n.Pos())
 		w.typ(n.Type())
-		w.elemList(n.List()) // special handling of field names
+		w.fieldList(n.List()) // special handling of field names
 
 	case ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT:
 		w.op(ir.OCOMPLIT)
@@ -1349,7 +1380,7 @@ func (w *exportWriter) expr(n ir.Node) {
 
 	case ir.OCOPY, ir.OCOMPLEX:
 		// treated like other builtin calls (see e.g., OREAL)
-		w.op(op)
+		w.op(n.Op())
 		w.pos(n.Pos())
 		w.expr(n.Left())
 		w.expr(n.Right())
@@ -1361,20 +1392,21 @@ func (w *exportWriter) expr(n ir.Node) {
 		w.expr(n.Left())
 		w.typ(n.Type())
 
-	case ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.OCAP, ir.OCLOSE, ir.ODELETE, ir.OLEN, ir.OMAKE, ir.ONEW, ir.OPANIC, ir.ORECOVER, ir.OPRINT, ir.OPRINTN:
+	case ir.OREAL, ir.OIMAG, ir.OCAP, ir.OCLOSE, ir.OLEN, ir.ONEW, ir.OPANIC:
-		w.op(op)
+		w.op(n.Op())
 		w.pos(n.Pos())
-		if n.Left() != nil {
+		w.expr(n.Left())
-			w.expr(n.Left())
+		w.op(ir.OEND)
-			w.op(ir.OEND)
+
-		} else {
+	case ir.OAPPEND, ir.ODELETE, ir.ORECOVER, ir.OPRINT, ir.OPRINTN:
-			w.exprList(n.List()) // emits terminating OEND
+		w.op(n.Op())
-		}
+		w.pos(n.Pos())
+		w.exprList(n.List()) // emits terminating OEND
 		// only append() calls may contain '...' arguments
-		if op == ir.OAPPEND {
+		if n.Op() == ir.OAPPEND {
 			w.bool(n.IsDDD())
 		} else if n.IsDDD() {
-			base.Fatalf("exporter: unexpected '...' with %v call", op)
+			base.Fatalf("exporter: unexpected '...' with %v call", n.Op())
 		}
 
 	case ir.OCALL, ir.OCALLFUNC, ir.OCALLMETH, ir.OCALLINTER, ir.OGETG:
@@ -1386,15 +1418,13 @@ func (w *exportWriter) expr(n ir.Node) {
 		w.bool(n.IsDDD())
 
 	case ir.OMAKEMAP, ir.OMAKECHAN, ir.OMAKESLICE:
-		w.op(op) // must keep separate from OMAKE for importer
+		w.op(n.Op()) // must keep separate from OMAKE for importer
 		w.pos(n.Pos())
 		w.typ(n.Type())
 		switch {
 		default:
 			// empty list
 			w.op(ir.OEND)
-		case n.List().Len() != 0: // pre-typecheck
-			w.exprList(n.List()) // emits terminating OEND
 		case n.Right() != nil:
 			w.expr(n.Left())
 			w.expr(n.Right())
@@ -1405,15 +1435,37 @@ func (w *exportWriter) expr(n ir.Node) {
 		}
 
 	// unary expressions
-	case ir.OPLUS, ir.ONEG, ir.OADDR, ir.OBITNOT, ir.ODEREF, ir.ONOT, ir.ORECV:
+	case ir.OPLUS, ir.ONEG, ir.OBITNOT, ir.ONOT, ir.ORECV:
-		w.op(op)
+		w.op(n.Op())
 		w.pos(n.Pos())
 		w.expr(n.Left())
 
+	case ir.OADDR:
+		w.op(n.Op())
+		w.pos(n.Pos())
+		w.expr(n.Left())
+
+	case ir.ODEREF:
+		w.op(n.Op())
+		w.pos(n.Pos())
+		w.expr(n.Left())
+
+	case ir.OSEND:
+		w.op(n.Op())
+		w.pos(n.Pos())
+		w.expr(n.Left())
+		w.expr(n.Right())
+
 	// binary expressions
-	case ir.OADD, ir.OAND, ir.OANDAND, ir.OANDNOT, ir.ODIV, ir.OEQ, ir.OGE, ir.OGT, ir.OLE, ir.OLT,
+	case ir.OADD, ir.OAND, ir.OANDNOT, ir.ODIV, ir.OEQ, ir.OGE, ir.OGT, ir.OLE, ir.OLT,
-		ir.OLSH, ir.OMOD, ir.OMUL, ir.ONE, ir.OOR, ir.OOROR, ir.ORSH, ir.OSEND, ir.OSUB, ir.OXOR:
+		ir.OLSH, ir.OMOD, ir.OMUL, ir.ONE, ir.OOR, ir.ORSH, ir.OSUB, ir.OXOR:
-		w.op(op)
+		w.op(n.Op())
+		w.pos(n.Pos())
+		w.expr(n.Left())
+		w.expr(n.Right())
+
+	case ir.OANDAND, ir.OOROR:
+		w.op(n.Op())
 		w.pos(n.Pos())
 		w.expr(n.Left())
 		w.expr(n.Right())
@@ -1454,15 +1506,16 @@ func (w *exportWriter) exprsOrNil(a, b ir.Node) {
 	}
 }
 
-func (w *exportWriter) elemList(list ir.Nodes) {
+func (w *exportWriter) fieldList(list ir.Nodes) {
 	w.uint64(uint64(list.Len()))
 	for _, n := range list.Slice() {
+		n := n.(*ir.StructKeyExpr)
 		w.selector(n.Sym())
 		w.expr(n.Left())
 	}
 }
 
-func (w *exportWriter) localName(n ir.Node) {
+func (w *exportWriter) localName(n *ir.Name) {
 	// Escape analysis happens after inline bodies are saved, but
 	// we're using the same ONAME nodes, so we might still see
 	// PAUTOHEAP here.

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

@@ -753,7 +753,7 @@ func (r *importReader) stmtList() []ir.Node {
 }
 
 func (r *importReader) caseList(sw ir.Node) []ir.Node {
-	namedTypeSwitch := sw.Op() == ir.OSWITCH && sw.Left() != nil && sw.Left().Op() == ir.OTYPESW && sw.Left().Left() != nil
+	namedTypeSwitch := isNamedTypeSwitch(sw)
 
 	cases := make([]ir.Node, r.uint64())
 	for i := range cases {
@@ -766,7 +766,7 @@ func (r *importReader) caseList(sw ir.Node) []ir.Node {
 			caseVar := ir.NewNameAt(cas.Pos(), r.ident())
 			declare(caseVar, dclcontext)
 			cas.PtrRlist().Set1(caseVar)
-			caseVar.Defn = sw.Left()
+			caseVar.Defn = sw.(*ir.SwitchStmt).Left()
 		}
 		cas.PtrBody().Set(r.stmtList())
 		cases[i] = cas
@@ -915,14 +915,14 @@ func (r *importReader) node() ir.Node {
 		return n
 
 	case ir.OCOPY, ir.OCOMPLEX, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.OCAP, ir.OCLOSE, ir.ODELETE, ir.OLEN, ir.OMAKE, ir.ONEW, ir.OPANIC, ir.ORECOVER, ir.OPRINT, ir.OPRINTN:
-		n := npos(r.pos(), builtinCall(op))
+		n := builtinCall(r.pos(), op)
 		n.PtrList().Set(r.exprList())
 		if op == ir.OAPPEND {
 			n.SetIsDDD(r.bool())
 		}
 		return n
 
-	// case OCALL, OCALLFUNC, OCALLMETH, OCALLINTER, OGETG:
+	// case OCALLFUNC, OCALLMETH, OCALLINTER, OGETG:
 	// 	unreachable - mapped to OCALL case below by exporter
 
 	case ir.OCALL:
@@ -934,7 +934,7 @@ func (r *importReader) node() ir.Node {
 		return n
 
 	case ir.OMAKEMAP, ir.OMAKECHAN, ir.OMAKESLICE:
-		n := npos(r.pos(), builtinCall(ir.OMAKE))
+		n := builtinCall(r.pos(), ir.OMAKE)
 		n.PtrList().Append(ir.TypeNode(r.typ()))
 		n.PtrList().Append(r.exprList()...)
 		return n
@@ -1042,8 +1042,7 @@ func (r *importReader) node() ir.Node {
 	case ir.OSELECT:
 		n := ir.NodAt(r.pos(), ir.OSELECT, nil, nil)
 		n.PtrInit().Set(r.stmtList())
-		left, _ := r.exprsOrNil()
+		r.exprsOrNil() // TODO(rsc): Delete (and fix exporter). These are always nil.
-		n.SetLeft(left)
 		n.PtrList().Set(r.caseList(n))
 		return n
 
@@ -1110,3 +1109,12 @@ func (r *importReader) exprsOrNil() (a, b ir.Node) {
 	}
 	return
 }
+
+func builtinCall(pos src.XPos, op ir.Op) *ir.CallExpr {
+	return ir.NewCallExpr(pos, ir.OCALL, mkname(types.BuiltinPkg.Lookup(ir.OpNames[op])), nil)
+}
+
+func npos(pos src.XPos, n ir.Node) ir.Node {
+	n.SetPos(pos)
+	return n
+}