cmd/compile: clean the output of GOSSAFUNC

Since we print almost everything to ssa.html in the GOSSAFUNC mode,
there is a need to stop spamming stdout when user just wants to see
ssa.html.

This changes cleans output of the GOSSAFUNC debug mode.
To enable the dump of the debug data to stdout, one must
put suffix + after the function name like that:

GOSSAFUNC=Foo+

Otherwise gc will not print the IR and ASM to stdout after each phase.
AST IR is still sent to stdout because it is not included
into ssa.html. It will be fixed in a separate change.

The change adds printing out the full path to the ssa.html file.

Updates #25942

Change-Id: I711e145e05f0443c7df5459ca528dced273a62ee
Reviewed-on: https://go-review.googlesource.com/126603
Run-TryBot: Yury Smolsky <yury@smolsky.by>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -428,6 +428,10 @@ func Main(archInit func(*Arch)) {
 	}
 
 	ssaDump = os.Getenv("GOSSAFUNC")
+	if strings.HasSuffix(ssaDump, "+") {
+		ssaDump = ssaDump[:len(ssaDump)-1]
+		ssaDumpStdout = true
+	}
 
 	trackScopes = flagDWARF
 

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

@@ -24,6 +24,7 @@ var ssaConfig *ssa.Config
 var ssaCaches []ssa.Cache
 
 var ssaDump string     // early copy of $GOSSAFUNC; the func name to dump output for
+var ssaDumpStdout bool // whether to dump to stdout
 const ssaDumpFile = "ssa.html"
 
 func initssaconfig() {
@@ -125,7 +126,7 @@ func buildssa(fn *Node, worker int) *ssa.Func {
 
 	fe := ssafn{
 		curfn: fn,
-		log:   printssa,
+		log:   printssa && ssaDumpStdout,
 	}
 	s.curfn = fn
 
@@ -4873,7 +4874,8 @@ func genssa(f *ssa.Func, pp *Progs) {
 	var progToBlock map[*obj.Prog]*ssa.Block
 	var valueToProgAfter []*obj.Prog // The first Prog following computation of a value v; v is visible at this point.
 	var logProgs = e.log
-	if logProgs {
+	if f.HTMLWriter != nil {
+		// logProgs can be false, meaning that we do not dump to the Stdout.
 		progToValue = make(map[*obj.Prog]*ssa.Value, f.NumValues())
 		progToBlock = make(map[*obj.Prog]*ssa.Block, f.NumBlocks())
 		f.Logf("genssa %s\n", f.Name)
@@ -5042,12 +5044,8 @@ func genssa(f *ssa.Func, pp *Progs) {
 			}
 			f.Logf(" %-6s\t%.5d (%s)\t%s\n", s, p.Pc, p.InnermostLineNumber(), p.InstructionString())
 		}
+	}
 	if f.HTMLWriter != nil {
-			// LineHist is defunct now - this code won't do
-			// anything.
-			// TODO: fix this (ideally without a global variable)
-			// saved := pp.Text.Ctxt.LineHist.PrintFilenameOnly
-			// pp.Text.Ctxt.LineHist.PrintFilenameOnly = true
 		var buf bytes.Buffer
 		buf.WriteString("<code>")
 		buf.WriteString("<dl class=\"ssa-gen\">")
@@ -5076,8 +5074,6 @@ func genssa(f *ssa.Func, pp *Progs) {
 		buf.WriteString("</dl>")
 		buf.WriteString("</code>")
 		f.HTMLWriter.WriteColumn("genssa", "genssa", "ssa-prog", buf.String())
-			// pp.Text.Ctxt.LineHist.PrintFilenameOnly = saved
-		}
 	}
 
 	defframe(&s, e)
@@ -5435,7 +5431,7 @@ type ssafn struct {
 	scratchFpMem *Node                  // temp for floating point register / memory moves on some architectures
 	stksize      int64                  // stack size for current frame
 	stkptrsize   int64                  // prefix of stack containing pointers
-	log          bool
+	log          bool                   // print ssa debug to the stdout
 }
 
 // StringData returns a symbol (a *types.Sym wrapped in an interface) which

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

@@ -42,7 +42,9 @@ func Compile(f *Func) {
 	}()
 
 	// Run all the passes
+	if f.Log() {
 		printFunc(f)
+	}
 	f.HTMLWriter.WriteFunc("start", "start", f)
 	if BuildDump != "" && BuildDump == f.Name {
 		f.dumpFile("build")
@@ -84,8 +86,10 @@ func Compile(f *Func) {
 				stats = fmt.Sprintf("[%d ns]", time)
 			}
 
+			if f.Log() {
 				f.Logf("  pass %s end %s\n", p.name, stats)
 				printFunc(f)
+			}
 			f.HTMLWriter.WriteFunc(phaseName, fmt.Sprintf("%s <span class=\"stats\">%s</span>", phaseName, stats), f)
 		}
 		if p.time || p.mem {

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

@@ -11,12 +11,14 @@ import (
 	"html"
 	"io"
 	"os"
+	"path/filepath"
 	"strings"
 )
 
 type HTMLWriter struct {
 	Logger
 	w    io.WriteCloser
+	path string
 }
 
 func NewHTMLWriter(path string, logger Logger, funcname string) *HTMLWriter {
@@ -24,7 +26,11 @@ func NewHTMLWriter(path string, logger Logger, funcname string) *HTMLWriter {
 	if err != nil {
 		logger.Fatalf(src.NoXPos, "%v", err)
 	}
-	html := HTMLWriter{w: out, Logger: logger}
+	pwd, err := os.Getwd()
+	if err != nil {
+		logger.Fatalf(src.NoXPos, "%v", err)
+	}
+	html := HTMLWriter{w: out, Logger: logger, path: filepath.Join(pwd, path)}
 	html.start(funcname)
 	return &html
 }
@@ -439,6 +445,7 @@ func (w *HTMLWriter) Close() {
 	io.WriteString(w.w, "</body>")
 	io.WriteString(w.w, "</html>")
 	w.w.Close()
+	fmt.Printf("dumped SSA to %v\n", w.path)
 }
 
 // WriteFunc writes f in a column headed by title.