cmd/compile: make use of types2.InitOrder

types2 already computes the order that package-level variables need to
be initialized in. Start using it.

Change-Id: Idf2740f963b8146f7c927f57effdbf245f41d355
Reviewed-on: https://go-review.googlesource.com/c/go/+/517617
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

2 files changed, 33 insertions, 28 deletions

diff --git a/src/cmd/compile/internal/noder/reader.go b/src/cmd/compile/internal/noder/reader.go
index 6dec060c8c..f63040ae13 100644
--- a/src/cmd/compile/internal/noder/reader.go
+++ b/src/cmd/compile/internal/noder/reader.go
@@ -3305,6 +3305,30 @@ func (r *reader) pkgInit(self *types.Pkg, target *ir.Package) {
 
 	r.pkgDecls(target)
 
+	initOrder := make([]ir.Node, r.Len())
+	for i := range initOrder {
+		lhs := make([]ir.Node, r.Len())
+		for j := range lhs {
+			lhs[j] = r.obj()
+		}
+		rhs := r.expr()
+		pos := lhs[0].Pos()
+
+		var as ir.Node
+		if len(lhs) == 1 {
+			as = typecheck.Stmt(ir.NewAssignStmt(pos, lhs[0], rhs))
+		} else {
+			as = typecheck.Stmt(ir.NewAssignListStmt(pos, ir.OAS2, lhs, []ir.Node{rhs}))
+		}
+
+		for _, v := range lhs {
+			v.(*ir.Name).Defn = as
+		}
+
+		initOrder[i] = as
+	}
+	target.InitOrder = initOrder
+
 	r.Sync(pkgbits.SyncEOF)
 }
 
@@ -3331,27 +3355,7 @@ func (r *reader) pkgDecls(target *ir.Package) {
 			target.Decls = append(target.Decls, method.Nname.(*ir.Name).Func)
 
 		case declVar:
-			pos := r.pos()
 			names := r.pkgObjs(target)
-			values := r.exprList()
-
-			if len(names) > 1 && len(values) == 1 {
-				as := ir.NewAssignListStmt(pos, ir.OAS2, nil, values)
-				for _, name := range names {
-					as.Lhs.Append(name)
-					name.Defn = as
-				}
-				target.Decls = append(target.Decls, as)
-			} else {
-				for i, name := range names {
-					as := ir.NewAssignStmt(pos, name, nil)
-					if i < len(values) {
-						as.Y = values[i]
-					}
-					name.Defn = as
-					target.Decls = append(target.Decls, as)
-				}
-			}
 
 			if n := r.Len(); n > 0 {
 				assert(len(names) == 1)
diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go
index 1d8c0bf933..77708245ae 100644
--- a/src/cmd/compile/internal/noder/writer.go
+++ b/src/cmd/compile/internal/noder/writer.go
@@ -2534,6 +2534,15 @@ func (w *writer) pkgInit(noders []*noder) {
 	}
 	w.Code(declEnd)
 
+	w.Len(len(w.p.info.InitOrder))
+	for _, init := range w.p.info.InitOrder {
+		w.Len(len(init.Lhs))
+		for _, v := range init.Lhs {
+			w.obj(v, nil)
+		}
+		w.expr(init.Rhs)
+	}
+
 	w.Sync(pkgbits.SyncEOF)
 }
 
@@ -2591,16 +2600,8 @@ func (w *writer) pkgDecl(decl syntax.Decl) {
 
 	case *syntax.VarDecl:
 		w.Code(declVar)
-		w.pos(decl)
 		w.pkgObjs(decl.NameList...)
 
-		// TODO(mdempsky): It would make sense to use multiExpr here, but
-		// that results in IR that confuses pkginit/initorder.go. So we
-		// continue using exprList, and let typecheck handle inserting any
-		// implicit conversions. That's okay though, because package-scope
-		// assignments never require dictionaries.
-		w.exprList(decl.Values)
-
 		var embeds []pragmaEmbed
 		if p, ok := decl.Pragma.(*pragmas); ok {
 			embeds = p.Embeds