cmd/compile: eliminate pushedio and savedstate

While here, get drop the lexlineno{++,--} hacks for canned imports.
They were added in commit d3237f9a, but don't seem to serve any
purpose.

Change-Id: I00f9e6be0ae9f217f2fa113b85e041dfd0303757
Reviewed-on: https://go-review.googlesource.com/19652Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>

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

@@ -451,8 +451,6 @@ var dotlist [10]Dlist // size is max depth of embeddeds
 
 var curio Io
 
-var pushedio Io
-
 var lexlineno int32
 
 var lineno int32

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

@@ -320,22 +320,15 @@ func Main() {
 
 		linehistpush(infile)
 
-		var err error
-		curio.bin, err = obj.Bopenr(infile)
+		bin, err := obj.Bopenr(infile)
 		if err != nil {
 			fmt.Printf("open %s: %v\n", infile, err)
 			errorexit()
 		}
 
-		curio.peekc = 0
-		curio.peekc1 = 0
-		curio.nlsemi = false
-		curio.eofnl = false
-		curio.last = 0
-
 		// Skip initial BOM if present.
-		if obj.Bgetrune(curio.bin) != BOM {
-			obj.Bungetrune(curio.bin)
+		if obj.Bgetrune(bin) != BOM {
+			obj.Bungetrune(bin)
 		}
 
 		block = 1
@@ -343,15 +336,13 @@ func Main() {
 
 		imported_unsafe = false
 
-		parse_file()
+		parse_file(bin)
 		if nsyntaxerrors != 0 {
 			errorexit()
 		}
 
 		linehistpop()
-		if curio.bin != nil {
-			obj.Bterm(curio.bin)
-		}
+		obj.Bterm(bin)
 	}
 
 	testdclstack()
@@ -667,14 +658,16 @@ func loadsys() {
 
 	block = 1
 	iota_ = -1000000
+	incannedimport = 1
 
 	importpkg = Runtimepkg
-	cannedimports("runtime.Builtin", runtimeimport)
+	parse_import(obj.Binitr(strings.NewReader(runtimeimport)))
 
 	importpkg = unsafepkg
-	cannedimports("unsafe.o", unsafeimport)
+	parse_import(obj.Binitr(strings.NewReader(unsafeimport)))
 
 	importpkg = nil
+	incannedimport = 0
 }
 
 func importfile(f *Val) {
@@ -822,15 +815,7 @@ func importfile(f *Val) {
 	switch c {
 	case '\n':
 		// old export format
-		pushedio = curio
-		curio = Io{bin: imp}
-		typecheckok = true
-
-		parse_import()
-
-		typecheckok = false
-		curio = pushedio
-		pushedio.bin = nil
+		parse_import(imp)
 
 	case 'B':
 		// new export format
@@ -847,22 +832,6 @@ func importfile(f *Val) {
 	}
 }
 
-func cannedimports(file string, cp string) {
-	lexlineno++ // if sys.6 is included on line 1,
-	pushedio = curio
-	curio = Io{bin: obj.Binitr(strings.NewReader(cp))}
-	typecheckok = true
-	incannedimport = 1
-
-	parse_import()
-
-	typecheckok = false
-	incannedimport = 0
-	curio = pushedio
-	pushedio.bin = nil
-	lexlineno-- // re correct sys.6 line number
-}
-
 func isSpace(c int) bool {
 	return c == ' ' || c == '\t' || c == '\n' || c == '\r'
 }

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

@@ -13,6 +13,7 @@ package gc
 // to handle optional commas and semicolons before a closing ) or } .
 
 import (
+	"cmd/internal/obj"
 	"fmt"
 	"strconv"
 	"strings"
@@ -24,7 +25,10 @@ const trace = false // if set, parse tracing can be enabled with -x
 // we can get rid of this (issue 13242).
 var fileparser parser // the Go source file parser in use
 
-func parse_import() {
+func parse_import(bin *obj.Biobuf) {
+	pushedio := curio
+	curio = Io{bin: bin}
+
 	// Indentation (for tracing) must be preserved across parsers
 	// since we are changing the lexer source (and parser state)
 	// under foot, in the middle of productions. This won't be
@@ -35,10 +39,14 @@ func parse_import() {
 	importparser := parser{indent: fileparser.indent} // preserve indentation
 	importparser.next()
 	importparser.import_package()
+
+	curio = pushedio
 }
 
 // parse_file sets up a new parser and parses a single Go source file.
-func parse_file() {
+func parse_file(bin *obj.Biobuf) {
+	curio = Io{bin: bin}
+
 	fileparser = parser{}
 	fileparser.next()
 	fileparser.file()
@@ -428,6 +436,7 @@ func (p *parser) import_package() {
 	}
 	importpkg.Safe = importsafe
 
+	typecheckok = true
 	defercheckwidth()
 
 	p.hidden_import_list()
@@ -438,6 +447,7 @@ func (p *parser) import_package() {
 	}
 
 	resumecheckwidth()
+	typecheckok = false
 }
 
 // Declaration = ConstDecl | TypeDecl | VarDecl .