[dev.ssa] cmd/compile: add HTML SSA printer

This is an initial implementation.
There are many rough edges and TODOs,
which will hopefully be polished out
with use.

Fixes #12071.

Change-Id: I1d6fd5a343063b5200623bceef2c2cfcc885794e
Reviewed-on: https://go-review.googlesource.com/13472Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -5,7 +5,9 @@
 package gc
 
 import (
+	"bytes"
 	"fmt"
+	"html"
 	"os"
 	"strings"
 
@@ -40,6 +42,18 @@ func buildssa(fn *Node) (ssafn *ssa.Func, usessa bool) {
 	s.f = s.config.NewFunc()
 	s.f.Name = name
 
+	if name == os.Getenv("GOSSAFUNC") {
+		// TODO: tempfile? it is handy to have the location
+		// of this file be stable, so you can just reload in the browser.
+		s.config.HTML = ssa.NewHTMLWriter("ssa.html", &s, name)
+		// TODO: generate and print a mapping from nodes to values and blocks
+	}
+	defer func() {
+		if !usessa {
+			s.config.HTML.Close()
+		}
+	}()
+
 	// If SSA support for the function is incomplete,
 	// assume that any panics are due to violated
 	// invariants. Swallow them silently.
@@ -1811,6 +1825,30 @@ func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
 			}
 			f.Logf("%s\t%s\n", s, p)
 		}
+		if f.Config.HTML != nil {
+			saved := ptxt.Ctxt.LineHist.PrintFilenameOnly
+			ptxt.Ctxt.LineHist.PrintFilenameOnly = true
+			var buf bytes.Buffer
+			buf.WriteString("<code>")
+			buf.WriteString("<dl class=\"ssa-gen\">")
+			for p := ptxt; p != nil; p = p.Link {
+				buf.WriteString("<dt class=\"ssa-prog-src\">")
+				if v, ok := valueProgs[p]; ok {
+					buf.WriteString(v.HTML())
+				} else if b, ok := blockProgs[p]; ok {
+					buf.WriteString(b.HTML())
+				}
+				buf.WriteString("</dt>")
+				buf.WriteString("<dd class=\"ssa-prog\">")
+				buf.WriteString(html.EscapeString(p.String()))
+				buf.WriteString("</dd>")
+				buf.WriteString("</li>")
+			}
+			buf.WriteString("</dl>")
+			buf.WriteString("</code>")
+			f.Config.HTML.WriteColumn("genssa", buf.String())
+			ptxt.Ctxt.LineHist.PrintFilenameOnly = saved
+		}
 	}
 
 	// Emit static data
@@ -1834,6 +1872,8 @@ func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
 	ggloblsym(gcargs, 4, obj.RODATA|obj.DUPOK)
 	duint32(gclocals, 0, 0)
 	ggloblsym(gclocals, 4, obj.RODATA|obj.DUPOK)
+
+	f.Config.HTML.Close()
 }
 
 func genValue(v *ssa.Value) {

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

@@ -34,13 +34,16 @@ func Compile(f *Func) {
 
 	// Run all the passes
 	printFunc(f)
+	f.Config.HTML.WriteFunc("start", f)
 	checkFunc(f)
 	for _, p := range passes {
 		phaseName = p.name
 		f.Logf("  pass %s begin\n", p.name)
+		// TODO: capture logging during this pass, add it to the HTML
 		p.fn(f)
 		f.Logf("  pass %s end\n", p.name)
 		printFunc(f)
+		f.Config.HTML.WriteFunc("after "+phaseName, f)
 		checkFunc(f)
 	}
 

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

@@ -11,6 +11,7 @@ type Config struct {
 	lowerBlock func(*Block) bool          // lowering function
 	lowerValue func(*Value, *Config) bool // lowering function
 	fe         Frontend                   // callbacks into compiler frontend
+	HTML       *HTMLWriter                // html writer, for debugging
 
 	// TODO: more stuff.  Compiler flags of interest, ...
 }
@@ -31,12 +32,7 @@ type TypeSource interface {
 	TypeBytePtr() Type // TODO: use unsafe.Pointer instead?
 }
 
-type Frontend interface {
-	TypeSource
-
-	// StringData returns a symbol pointing to the given string's contents.
-	StringData(string) interface{} // returns *gc.Sym
-
+type Logger interface {
 	// Log logs a message from the compiler.
 	Logf(string, ...interface{})
 
@@ -48,6 +44,14 @@ type Frontend interface {
 	Unimplementedf(msg string, args ...interface{})
 }
 
+type Frontend interface {
+	TypeSource
+	Logger
+
+	// StringData returns a symbol pointing to the given string's contents.
+	StringData(string) interface{} // returns *gc.Sym
+}
+
 // NewConfig returns a new configuration object for the given architecture.
 func NewConfig(arch string, fe Frontend) *Config {
 	c := &Config{arch: arch, fe: fe}

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

@@ -4,10 +4,10 @@
 
 package ssa
 
-// deadcode removes dead code from f.
-func deadcode(f *Func) {
+// findlive returns the reachable blocks and live values in f.
+func findlive(f *Func) (reachable []bool, live []bool) {
 	// Find all reachable basic blocks.
-	reachable := make([]bool, f.NumBlocks())
+	reachable = make([]bool, f.NumBlocks())
 	reachable[f.Entry.ID] = true
 	p := []*Block{f.Entry} // stack-like worklist
 	for len(p) > 0 {
@@ -24,8 +24,8 @@ func deadcode(f *Func) {
 	}
 
 	// Find all live values
-	live := make([]bool, f.NumValues()) // flag to set for each live value
-	var q []*Value                      // stack-like worklist of unscanned values
+	live = make([]bool, f.NumValues()) // flag to set for each live value
+	var q []*Value                     // stack-like worklist of unscanned values
 
 	// Starting set: all control values of reachable blocks are live.
 	for _, b := range f.Blocks {
@@ -54,6 +54,13 @@ func deadcode(f *Func) {
 		}
 	}
 
+	return reachable, live
+}
+
+// deadcode removes dead code from f.
+func deadcode(f *Func) {
+	reachable, live := findlive(f)
+
 	// Remove dead values from blocks' value list.  Return dead
 	// value ids to the allocator.
 	for _, b := range f.Blocks {

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

@@ -16,33 +16,77 @@ func printFunc(f *Func) {
 
 func (f *Func) String() string {
 	var buf bytes.Buffer
-	fprintFunc(&buf, f)
+	p := stringFuncPrinter{w: &buf}
+	fprintFunc(p, f)
 	return buf.String()
 }
 
-func fprintFunc(w io.Writer, f *Func) {
-	fmt.Fprint(w, f.Name)
-	fmt.Fprint(w, " ")
-	fmt.Fprintln(w, f.Type)
+type funcPrinter interface {
+	header(f *Func)
+	startBlock(b *Block, reachable bool)
+	endBlock(b *Block)
+	value(v *Value, live bool)
+	startDepCycle()
+	endDepCycle()
+}
+
+type stringFuncPrinter struct {
+	w io.Writer
+}
+
+func (p stringFuncPrinter) header(f *Func) {
+	fmt.Fprint(p.w, f.Name)
+	fmt.Fprint(p.w, " ")
+	fmt.Fprintln(p.w, f.Type)
+}
+
+func (p stringFuncPrinter) startBlock(b *Block, reachable bool) {
+	fmt.Fprintf(p.w, "  b%d:", b.ID)
+	if len(b.Preds) > 0 {
+		io.WriteString(p.w, " <-")
+		for _, pred := range b.Preds {
+			fmt.Fprintf(p.w, " b%d", pred.ID)
+		}
+	}
+	if !reachable {
+		fmt.Fprint(p.w, " DEAD")
+	}
+	io.WriteString(p.w, "\n")
+}
+
+func (p stringFuncPrinter) endBlock(b *Block) {
+	fmt.Fprintln(p.w, "    "+b.LongString())
+}
+
+func (p stringFuncPrinter) value(v *Value, live bool) {
+	fmt.Fprint(p.w, "    ")
+	fmt.Fprint(p.w, v.LongString())
+	if !live {
+		fmt.Fprint(p.w, " DEAD")
+	}
+	fmt.Fprintln(p.w)
+}
+
+func (p stringFuncPrinter) startDepCycle() {
+	fmt.Fprintln(p.w, "dependency cycle!")
+}
+
+func (p stringFuncPrinter) endDepCycle() {}
+
+func fprintFunc(p funcPrinter, f *Func) {
+	reachable, live := findlive(f)
+	p.header(f)
 	printed := make([]bool, f.NumValues())
 	for _, b := range f.Blocks {
-		fmt.Fprintf(w, "  b%d:", b.ID)
-		if len(b.Preds) > 0 {
-			io.WriteString(w, " <-")
-			for _, pred := range b.Preds {
-				fmt.Fprintf(w, " b%d", pred.ID)
-			}
-		}
-		io.WriteString(w, "\n")
+		p.startBlock(b, reachable[b.ID])
 
 		if f.scheduled {
 			// Order of Values has been decided - print in that order.
 			for _, v := range b.Values {
-				fmt.Fprint(w, "    ")
-				fmt.Fprintln(w, v.LongString())
+				p.value(v, live[v.ID])
 				printed[v.ID] = true
 			}
-			fmt.Fprintln(w, "    "+b.LongString())
+			p.endBlock(b)
 			continue
 		}
 
@@ -52,8 +96,7 @@ func fprintFunc(w io.Writer, f *Func) {
 			if v.Op != OpPhi {
 				continue
 			}
-			fmt.Fprint(w, "    ")
-			fmt.Fprintln(w, v.LongString())
+			p.value(v, live[v.ID])
 			printed[v.ID] = true
 			n++
 		}
@@ -73,25 +116,24 @@ func fprintFunc(w io.Writer, f *Func) {
 						continue outer
 					}
 				}
-				fmt.Fprint(w, "    ")
-				fmt.Fprintln(w, v.LongString())
+				p.value(v, live[v.ID])
 				printed[v.ID] = true
 				n++
 			}
 			if m == n {
-				fmt.Fprintln(w, "dependency cycle!")
+				p.startDepCycle()
 				for _, v := range b.Values {
 					if printed[v.ID] {
 						continue
 					}
-					fmt.Fprint(w, "    ")
-					fmt.Fprintln(w, v.LongString())
+					p.value(v, live[v.ID])
 					printed[v.ID] = true
 					n++
 				}
+				p.endDepCycle()
 			}
 		}
 
-		fmt.Fprintln(w, "    "+b.LongString())
+		p.endBlock(b)
 	}
 }

src/cmd/internal/obj/obj.go

@@ -25,12 +25,13 @@ import (
 //	  together, so that given (only) calls Push(10, "x.go", 1) and Pop(15),
 //	  virtual line 12 corresponds to x.go line 3.
 type LineHist struct {
-	Top            *LineStack  // current top of stack
-	Ranges         []LineRange // ranges for lookup
-	Dir            string      // directory to qualify relative paths
-	TrimPathPrefix string      // remove leading TrimPath from recorded file names
-	GOROOT         string      // current GOROOT
-	GOROOT_FINAL   string      // target GOROOT
+	Top               *LineStack  // current top of stack
+	Ranges            []LineRange // ranges for lookup
+	Dir               string      // directory to qualify relative paths
+	TrimPathPrefix    string      // remove leading TrimPath from recorded file names
+	PrintFilenameOnly bool        // ignore path when pretty-printing a line; internal use only
+	GOROOT            string      // current GOROOT
+	GOROOT_FINAL      string      // target GOROOT
 }
 
 // A LineStack is an entry in the recorded line history.
@@ -221,20 +222,24 @@ func (h *LineHist) LineString(lineno int) string {
 		return "<unknown line number>"
 	}
 
-	text := fmt.Sprintf("%s:%d", stk.File, stk.fileLineAt(lineno))
+	filename := stk.File
+	if h.PrintFilenameOnly {
+		filename = filepath.Base(filename)
+	}
+	text := fmt.Sprintf("%s:%d", filename, stk.fileLineAt(lineno))
 	if stk.Directive && stk.Parent != nil {
 		stk = stk.Parent
-		text += fmt.Sprintf("[%s:%d]", stk.File, stk.fileLineAt(lineno))
+		text += fmt.Sprintf("[%s:%d]", filename, stk.fileLineAt(lineno))
 	}
 	const showFullStack = false // was used by old C compilers
 	if showFullStack {
 		for stk.Parent != nil {
 			lineno = stk.Lineno - 1
 			stk = stk.Parent
-			text += fmt.Sprintf(" %s:%d", stk.File, stk.fileLineAt(lineno))
+			text += fmt.Sprintf(" %s:%d", filename, stk.fileLineAt(lineno))
 			if stk.Directive && stk.Parent != nil {
 				stk = stk.Parent
-				text += fmt.Sprintf("[%s:%d]", stk.File, stk.fileLineAt(lineno))
+				text += fmt.Sprintf("[%s:%d]", filename, stk.fileLineAt(lineno))
 			}
 		}
 	}