[dev.inline] cmd/internal/src: introduce compact source position representation

XPos is a compact (8 instead of 16 bytes on a 64bit machine) source
position representation. There is a 1:1 correspondence between each
XPos and each regular Pos, translated via a global table.

In some sense this brings back the LineHist, though positions can
track line and column information; there is a O(1) translation
between the representations (no binary search), and the translation
is factored out.

The size increase with the prior change is brought down again and
the compiler speed is in line with the master repo (measured on
the same "quiet" machine as for prior change):

name       old time/op     new time/op     delta
Template       256ms ± 1%      262ms ± 2%    ~             (p=0.063 n=5+4)
Unicode        132ms ± 1%      135ms ± 2%    ~             (p=0.063 n=5+4)
GoTypes        891ms ± 1%      871ms ± 1%  -2.28%          (p=0.016 n=5+4)
Compiler       3.84s ± 2%      3.89s ± 2%    ~             (p=0.413 n=5+4)
MakeBash       47.1s ± 1%      46.2s ± 2%    ~             (p=0.095 n=5+5)

name       old user-ns/op  new user-ns/op  delta
Template        309M ± 1%       314M ± 2%    ~             (p=0.111 n=5+4)
Unicode         165M ± 1%       172M ± 9%    ~             (p=0.151 n=5+5)
GoTypes        1.14G ± 2%      1.12G ± 1%    ~             (p=0.063 n=5+4)
Compiler       5.00G ± 1%      4.96G ± 1%    ~             (p=0.286 n=5+4)

Change-Id: Icc570cc60ab014d8d9af6976f1f961ab8828cc47
Reviewed-on: https://go-review.googlesource.com/34506
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 7 insertions, 7 deletions

diff --git a/src/cmd/compile/internal/gc/noder.go b/src/cmd/compile/internal/gc/noder.go
index 7376814b43..d7e3023102 100644
--- a/src/cmd/compile/internal/gc/noder.go
+++ b/src/cmd/compile/internal/gc/noder.go
@@ -69,7 +69,7 @@ func (p *noder) file(file *syntax.File) {
 	// for fninit and set lineno to NoPos here.
 	// TODO(gri) fix this once we switched permanently to the new
 	// position information.
-	lineno = src.MakePos(file.Pos().Base(), uint(file.Lines), 0)
+	lineno = MakePos(file.Pos().Base(), uint(file.Lines), 0)
 }
 
 func (p *noder) decls(decls []syntax.Decl) (l []*Node) {
@@ -249,7 +249,7 @@ func (p *noder) funcDecl(fun *syntax.FuncDecl) *Node {
 		yyerror("can only use //go:noescape with external func implementations")
 	}
 	f.Func.Pragma = pragma
-	lineno = src.MakePos(fun.Pos().Base(), fun.EndLine, 0)
+	lineno = MakePos(fun.Pos().Base(), fun.EndLine, 0)
 	f.Func.Endlineno = lineno
 
 	funcbody(f)
@@ -375,14 +375,14 @@ func (p *noder) expr(expr syntax.Expr) *Node {
 			l[i] = p.wrapname(expr.ElemList[i], e)
 		}
 		n.List.Set(l)
-		lineno = src.MakePos(expr.Pos().Base(), expr.EndLine, 0)
+		lineno = MakePos(expr.Pos().Base(), expr.EndLine, 0)
 		return n
 	case *syntax.KeyValueExpr:
 		return p.nod(expr, OKEY, p.expr(expr.Key), p.wrapname(expr.Value, p.expr(expr.Value)))
 	case *syntax.FuncLit:
 		closurehdr(p.typeExpr(expr.Type))
 		body := p.stmts(expr.Body)
-		lineno = src.MakePos(expr.Pos().Base(), expr.EndLine, 0)
+		lineno = MakePos(expr.Pos().Base(), expr.EndLine, 0)
 		return p.setlineno(expr, closurebody(body))
 	case *syntax.ParenExpr:
 		return p.nod(expr, OPAREN, p.expr(expr.X), nil)
@@ -1009,7 +1009,7 @@ func (p *noder) setlineno(src_ syntax.Node, dst *Node) *Node {
 		// TODO(mdempsky): Shouldn't happen. Fix package syntax.
 		return dst
 	}
-	dst.Pos = pos
+	dst.Pos = Ctxt.PosTable.XPos(pos)
 	return dst
 }
 
@@ -1022,12 +1022,12 @@ func (p *noder) lineno(n syntax.Node) {
 		// TODO(mdempsky): Shouldn't happen. Fix package syntax.
 		return
 	}
-	lineno = pos
+	lineno = Ctxt.PosTable.XPos(pos)
 }
 
 func (p *noder) error(err error) {
 	e := err.(syntax.Error)
-	yyerrorl(e.Pos, "%s", e.Msg)
+	yyerrorl(Ctxt.PosTable.XPos(e.Pos), "%s", e.Msg)
 }
 
 func (p *noder) pragma(pos src.Pos, text string) syntax.Pragma {