[dev.inline] cmd/compile: reorganize file parsing logic

Preparation for concurrent parsing. No behavior change.

Change-Id: Ic1ec45fc3cb316778c29065cf055c82e92ffa874
Reviewed-on: https://go-review.googlesource.com/35125
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -325,16 +325,7 @@ func Main() {
 	loadsys()
 
 	timings.Start("fe", "parse")
-	var lines uint
+	lines := parseFiles(flag.Args())
-	for _, infile := range flag.Args() {
-		block = 1
-		iota_ = -1000000
-		imported_unsafe = false
-		lines += parseFile(infile)
-		if nsyntaxerrors != 0 {
-			errorexit()
-		}
-	}
 	timings.Stop()
 	timings.AddEvent(int64(lines), "lines")
 

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

@@ -16,6 +16,17 @@ import (
 	"cmd/internal/src"
 )
 
+func parseFiles(filenames []string) uint {
+	var lines uint
+	for _, filename := range filenames {
+		lines += parseFile(filename)
+		if nsyntaxerrors != 0 {
+			errorexit()
+		}
+	}
+	return lines
+}
+
 func parseFile(filename string) uint {
 	f, err := os.Open(filename)
 	if err != nil {
@@ -30,12 +41,6 @@ func parseFile(filename string) uint {
 
 	p.file(file)
 
-	if !imported_unsafe {
-		for _, pos := range p.linknames {
-			p.error(syntax.Error{Pos: pos, Msg: "//go:linkname only allowed in Go files that import \"unsafe\""})
-		}
-	}
-
 	if nsyntaxerrors == 0 {
 		testdclstack()
 	}
@@ -55,11 +60,21 @@ type noder struct {
 }
 
 func (p *noder) file(file *syntax.File) {
+	block = 1
+	iota_ = -1000000
+	imported_unsafe = false
+
 	p.lineno(file.PkgName)
 	mkpackage(file.PkgName.Value)
 
 	xtop = append(xtop, p.decls(file.DeclList)...)
 
+	if !imported_unsafe {
+		for _, pos := range p.linknames {
+			p.error(syntax.Error{Pos: pos, Msg: "//go:linkname only allowed in Go files that import \"unsafe\""})
+		}
+	}
+
 	// For compatibility with old code only (comparisons w/ toolstash):
 	// The old line number tracking simply continued incrementing the
 	// virtual line number (lexlineno) and using it also for lineno.