cmd/compile/internal/syntax: remove dependency on cmd/internal/src

For dependency reasons, the data structure implementing source positions in the compiler is in cmd/internal/src. It contains highly compiler specific details (e.g. inlining index). This change introduces a parallel but simpler position representation, defined in the syntax package, which removes that package's dependency on cmd/internal/src, and also removes the need to deal with certain filename-specific operations (defined by the needs of the compiler) in the syntax package. As a result, the syntax package becomes again a compiler- independent, stand-alone package that at some point might replace (or augment) the existing top-level go/* syntax-related packages. Additionally, line directives that update column numbers are now correctly tracked through the syntax package, with additional tests added. (The respective changes also need to be made in cmd/internal/src; i.e., the compiler accepts but still ignores column numbers in line directives.) This change comes at the cost of a new position translation step, but that step is cheap because it only needs to do real work if the position base changed (i.e., if there is a new file, or new line directive). There is no noticeable impact on overall compiler performance measured with `compilebench -count 5 -alloc`: name old time/op new time/op delta Template 220ms ± 8% 228ms ±18% ~ (p=0.548 n=5+5) Unicode 119ms ±11% 113ms ± 5% ~ (p=0.056 n=5+5) GoTypes 684ms ± 6% 677ms ± 3% ~ (p=0.841 n=5+5) Compiler 3.19s ± 7% 3.01s ± 1% ~ (p=0.095 n=5+5) SSA 7.92s ± 8% 7.79s ± 1% ~ (p=0.690 n=5+5) Flate 141ms ± 7% 139ms ± 4% ~ (p=0.548 n=5+5) GoParser 173ms ±12% 171ms ± 4% ~ (p=1.000 n=5+5) Reflect 417ms ± 5% 411ms ± 3% ~ (p=0.548 n=5+5) Tar 205ms ± 5% 198ms ± 2% ~ (p=0.690 n=5+5) XML 232ms ± 4% 229ms ± 4% ~ (p=0.690 n=5+5) StdCmd 28.7s ± 5% 28.2s ± 2% ~ (p=0.421 n=5+5) name old user-time/op new user-time/op delta Template 269ms ± 4% 265ms ± 5% ~ (p=0.421 n=5+5) Unicode 153ms ± 7% 149ms ± 3% ~ (p=0.841 n=5+5) GoTypes 850ms ± 7% 862ms ± 4% ~ (p=0.841 n=5+5) Compiler 4.01s ± 5% 3.86s ± 0% ~ (p=0.190 n=5+4) SSA 10.9s ± 4% 10.8s ± 2% ~ (p=0.548 n=5+5) Flate 166ms ± 7% 167ms ± 6% ~ (p=1.000 n=5+5) GoParser 204ms ± 8% 206ms ± 7% ~ (p=0.841 n=5+5) Reflect 514ms ± 5% 508ms ± 4% ~ (p=0.548 n=5+5) Tar 245ms ± 6% 244ms ± 3% ~ (p=0.690 n=5+5) XML 280ms ± 4% 278ms ± 4% ~ (p=0.841 n=5+5) name old alloc/op new alloc/op delta Template 37.9MB ± 0% 37.9MB ± 0% ~ (p=0.841 n=5+5) Unicode 28.8MB ± 0% 28.8MB ± 0% ~ (p=0.841 n=5+5) GoTypes 113MB ± 0% 113MB ± 0% ~ (p=0.151 n=5+5) Compiler 468MB ± 0% 468MB ± 0% -0.01% (p=0.032 n=5+5) SSA 1.50GB ± 0% 1.50GB ± 0% ~ (p=0.548 n=5+5) Flate 24.4MB ± 0% 24.4MB ± 0% ~ (p=1.000 n=5+5) GoParser 30.7MB ± 0% 30.7MB ± 0% ~ (p=1.000 n=5+5) Reflect 76.5MB ± 0% 76.5MB ± 0% ~ (p=0.548 n=5+5) Tar 38.9MB ± 0% 38.9MB ± 0% ~ (p=0.222 n=5+5) XML 41.6MB ± 0% 41.6MB ± 0% ~ (p=0.548 n=5+5) name old allocs/op new allocs/op delta Template 382k ± 0% 382k ± 0% +0.01% (p=0.008 n=5+5) Unicode 343k ± 0% 343k ± 0% ~ (p=0.841 n=5+5) GoTypes 1.19M ± 0% 1.19M ± 0% +0.01% (p=0.008 n=5+5) Compiler 4.53M ± 0% 4.53M ± 0% +0.03% (p=0.008 n=5+5) SSA 12.4M ± 0% 12.4M ± 0% +0.00% (p=0.008 n=5+5) Flate 235k ± 0% 235k ± 0% ~ (p=0.079 n=5+5) GoParser 318k ± 0% 318k ± 0% ~ (p=0.730 n=5+5) Reflect 978k ± 0% 978k ± 0% ~ (p=1.000 n=5+5) Tar 393k ± 0% 393k ± 0% ~ (p=0.056 n=5+5) XML 405k ± 0% 405k ± 0% ~ (p=0.548 n=5+5) name old text-bytes new text-bytes delta HelloSize 672kB ± 0% 672kB ± 0% ~ (all equal) CmdGoSize 7.12MB ± 0% 7.12MB ± 0% ~ (all equal) name old data-bytes new data-bytes delta HelloSize 133kB ± 0% 133kB ± 0% ~ (all equal) CmdGoSize 390kB ± 0% 390kB ± 0% ~ (all equal) name old exe-bytes new exe-bytes delta HelloSize 1.07MB ± 0% 1.07MB ± 0% ~ (all equal) CmdGoSize 11.2MB ± 0% 11.2MB ± 0% ~ (all equal) Passes toolstash compare. For #22662. Change-Id: I19edb53dd9675af57f7122cb7dba2a6d8bdcc3da Reviewed-on: https://go-review.googlesource.com/94515 Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2025-12-08 06:10:04 +00:00 · 2018-01-02 16:58:37 -08:00 · 2018-01-02 16:58:37 -08:00 · 5c08b9e8bd
commit 5c08b9e8bd
parent b1accced20
14 changed files with 309 additions and 151 deletions
--- a/src/cmd/compile/internal/syntax/pos.go
+++ b/src/cmd/compile/internal/syntax/pos.go
@ -0,0 +1,109 @@
+// Copyright 2018 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 syntax
+
+import "fmt"
+
+// PosMax is the largest line or column value that can be represented without loss.
+// Incoming values (arguments) larger than PosMax will be set to PosMax.
+const PosMax = 1 << 30
+
+// A Pos represents an absolute (line, col) source position
+// with a reference to position base for computing relative
+// (to a file, or line directive) position information.
+// Pos values are intentionally light-weight so that they
+// can be created without too much concern about space use.
+type Pos struct {
+	base      *PosBase
+	line, col uint32
+}
+
+// MakePos returns a new Pos for the given PosBase, line and column.
+func MakePos(base *PosBase, line, col uint) Pos { return Pos{base, sat32(line), sat32(col)} }
+
+// TODO(gri) IsKnown makes an assumption about linebase < 1.
+//           Maybe we should check for Base() != nil instead.
+
+func (pos Pos) IsKnown() bool  { return pos.line > 0 }
+func (pos Pos) Base() *PosBase { return pos.base }
+func (pos Pos) Line() uint     { return uint(pos.line) }
+func (pos Pos) Col() uint      { return uint(pos.col) }
+
+func (pos Pos) RelFilename() string { b := pos.Base(); return b.Filename() }
+func (pos Pos) RelLine() uint       { b := pos.Base(); return b.Line() + (pos.Line() - b.Pos().Line()) }
+func (pos Pos) RelCol() uint {
+	b := pos.Base()
+	if pos.Line() == b.Pos().Line() {
+		// pos on same line as pos base => column is relative to pos base
+		return b.Col() + (pos.Col() - b.Pos().Col())
+	}
+	return pos.Col()
+}
+
+func (pos Pos) String() string {
+	s := fmt.Sprintf("%s:%d:%d", pos.RelFilename(), pos.RelLine(), pos.RelCol())
+	if bpos := pos.Base().Pos(); bpos.IsKnown() {
+		s += fmt.Sprintf("[%s:%d:%d]", bpos.RelFilename(), pos.Line(), pos.Col())
+	}
+	return s
+}
+
+// A PosBase represents the base for relative position information:
+// At position pos, the relative position is filename:line:col.
+type PosBase struct {
+	pos       Pos
+	filename  string
+	line, col uint32
+}
+
+// NewFileBase returns a new PosBase for the given filename.
+// The PosBase position is unknown in this case.
+func NewFileBase(filename string) *PosBase {
+	return &PosBase{filename: filename}
+}
+
+// NewLineBase returns a new PosBase for a line directive "line filename:line:col"
+// relative to pos, which is the position of the character immediately following
+// the comment containing the line directive. For a directive in a line comment,
+// that position is the beginning of the next line (i.e., the newline character
+// belongs to the line comment).
+func NewLineBase(pos Pos, filename string, line, col uint) *PosBase {
+	return &PosBase{pos, filename, sat32(line), sat32(col)}
+}
+
+func (base *PosBase) Pos() (_ Pos) {
+	if base == nil {
+		return
+	}
+	return base.pos
+}
+
+func (base *PosBase) Filename() string {
+	if base == nil {
+		return ""
+	}
+	return base.filename
+}
+
+func (base *PosBase) Line() uint {
+	if base == nil {
+		return 0
+	}
+	return uint(base.line)
+}
+
+func (base *PosBase) Col() uint {
+	if base == nil {
+		return 0
+	}
+	return uint(base.col)
+}
+
+func sat32(x uint) uint32 {
+	if x > PosMax {
+		return PosMax
+	}
+	return uint32(x)
+}