cmd/compile: remove references to *os.File from ssa package

This reduces the size of the ssa export data
by 10%, from 76154 to 67886.

It doesn't appear that #20084, which would do this automatically,
is going to be fixed soon. Do it manually for now.

This speeds up compiling cmd/compile/internal/amd64
and presumably its comrades as well:

name          old time/op       new time/op       delta
CompileAMD64       89.6ms ± 6%       86.7ms ± 5%  -3.29%  (p=0.000 n=49+47)

name          old user-time/op  new user-time/op  delta
CompileAMD64        116ms ± 5%        112ms ± 5%  -3.51%  (p=0.000 n=45+42)

name          old alloc/op      new alloc/op      delta
CompileAMD64       26.7MB ± 0%       25.8MB ± 0%  -3.26%  (p=0.008 n=5+5)

name          old allocs/op     new allocs/op     delta
CompileAMD64         223k ± 0%         213k ± 0%  -4.46%  (p=0.008 n=5+5)

Updates #20084

Change-Id: I49e8951c5bfce63ad2b7f4fc3bfa0868c53114f9
Reviewed-on: https://go-review.googlesource.com/41493
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/ssa/func.go

@@ -8,11 +8,17 @@ import (
 	"cmd/internal/src"
 	"crypto/sha1"
 	"fmt"
+	"io"
 	"math"
 	"os"
 	"strings"
 )
 
+type writeSyncer interface {
+	io.Writer
+	Sync() error
+}
+
 // A Func represents a Go func declaration (or function literal) and its body.
 // This package compiles each Func independently.
 // Funcs are single-use; a new Func must be created for every compiled function.
@@ -30,7 +36,7 @@ type Func struct {
 
 	// Given an environment variable used for debug hash match,
 	// what file (if any) receives the yes/no logging?
-	logfiles   map[string]*os.File
+	logfiles   map[string]writeSyncer
 	HTMLWriter *HTMLWriter // html writer, for debugging
 	DebugTest  bool        // default true unless $GOSSAHASH != ""; as a debugging aid, make new code conditional on this and use GOSSAHASH to binary search for failing cases
 
@@ -590,7 +596,7 @@ func (f *Func) DebugHashMatch(evname, name string) bool {
 
 func (f *Func) logDebugHashMatch(evname, name string) {
 	if f.logfiles == nil {
-		f.logfiles = make(map[string]*os.File)
+		f.logfiles = make(map[string]writeSyncer)
 	}
 	file := f.logfiles[evname]
 	if file == nil {
@@ -604,8 +610,7 @@ func (f *Func) logDebugHashMatch(evname, name string) {
 		}
 		f.logfiles[evname] = file
 	}
-	s := fmt.Sprintf("%s triggered %s\n", evname, name)
-	file.WriteString(s)
+	fmt.Fprintf(file, "%s triggered %s\n", evname, name)
 	file.Sync()
 }
 

src/cmd/compile/internal/ssa/html.go

@@ -15,7 +15,7 @@ import (
 
 type HTMLWriter struct {
 	Logger
-	*os.File
+	w io.WriteCloser
 }
 
 func NewHTMLWriter(path string, logger Logger, funcname string) *HTMLWriter {
@@ -23,7 +23,7 @@ func NewHTMLWriter(path string, logger Logger, funcname string) *HTMLWriter {
 	if err != nil {
 		logger.Fatalf(src.NoXPos, "%v", err)
 	}
-	html := HTMLWriter{File: out, Logger: logger}
+	html := HTMLWriter{w: out, Logger: logger}
 	html.start(funcname)
 	return &html
 }
@@ -299,11 +299,11 @@ func (w *HTMLWriter) Close() {
 	if w == nil {
 		return
 	}
-	w.WriteString("</tr>")
-	w.WriteString("</table>")
-	w.WriteString("</body>")
-	w.WriteString("</html>")
-	w.File.Close()
+	io.WriteString(w.w, "</tr>")
+	io.WriteString(w.w, "</table>")
+	io.WriteString(w.w, "</body>")
+	io.WriteString(w.w, "</html>")
+	w.w.Close()
 }
 
 // WriteFunc writes f in a column headed by title.
@@ -328,13 +328,13 @@ func (w *HTMLWriter) WriteColumn(title string, html string) {
 }
 
 func (w *HTMLWriter) Printf(msg string, v ...interface{}) {
-	if _, err := fmt.Fprintf(w.File, msg, v...); err != nil {
+	if _, err := fmt.Fprintf(w.w, msg, v...); err != nil {
 		w.Fatalf(src.NoXPos, "%v", err)
 	}
 }
 
 func (w *HTMLWriter) WriteString(s string) {
-	if _, err := w.File.WriteString(s); err != nil {
+	if _, err := io.WriteString(w.w, s); err != nil {
 		w.Fatalf(src.NoXPos, "%v", err)
 	}
 }

src/cmd/compile/internal/ssa/rewrite.go

@@ -7,6 +7,7 @@ package ssa
 import (
 	"cmd/internal/obj"
 	"fmt"
+	"io"
 	"math"
 	"os"
 	"path/filepath"
@@ -561,7 +562,7 @@ func logRule(s string) {
 	}
 }
 
-var ruleFile *os.File
+var ruleFile io.Writer
 
 func min(x, y int64) int64 {
 	if x < y {