cmd/compile: combine ssa.html columns with identical contents

Combine columns in ssa.html output if they are identical. There
can now be multiple titles per column which are all clickable to
expand and collapse their column. Give collapsed columns some
padding for better readability. Some of the work in this CL was
started by Josh Bleecher Snyder and mailed to me in order to
continue to completion.

Updates #37766

Change-Id: I313b0917dc1bafe1eb99d91798ea915e5bcfaae9
Reviewed-on: https://go-review.googlesource.com/c/go/+/226209
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -19,9 +19,12 @@ import (
 
 type HTMLWriter struct {
 	Logger
-	w    io.WriteCloser
-	path string
-	dot  *dotWriter
+	w             io.WriteCloser
+	path          string
+	dot           *dotWriter
+	prevHash      []byte
+	pendingPhases []string
+	pendingTitles []string
 }
 
 func NewHTMLWriter(path string, logger Logger, funcname, cfgMask string) *HTMLWriter {
@@ -88,27 +91,22 @@ th, td {
 td > h2 {
     cursor: pointer;
     font-size: 120%;
+    margin: 5px 0px 5px 0px;
 }
 
 td.collapsed {
     font-size: 12px;
     width: 12px;
     border: 1px solid white;
-    padding: 0;
+    padding: 2px;
     cursor: pointer;
     background: #fafafa;
 }
 
-td.collapsed  div {
-     -moz-transform: rotate(-90.0deg);  /* FF3.5+ */
-       -o-transform: rotate(-90.0deg);  /* Opera 10.5 */
-  -webkit-transform: rotate(-90.0deg);  /* Saf3.1+, Chrome */
-             filter:  progid:DXImageTransform.Microsoft.BasicImage(rotation=0.083);  /* IE6,IE7 */
-         -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(rotation=0.083)"; /* IE8 */
-         margin-top: 10.3em;
-         margin-left: -10em;
-         margin-right: -10em;
-         text-align: right;
+td.collapsed div {
+    /* TODO: Flip the direction of the phase's title 90 degrees on a collapsed column. */
+    writing-mode: vertical-lr;
+    white-space: pre;
 }
 
 code, pre, .lines, .ast {
@@ -481,7 +479,7 @@ window.onload = function() {
         "deadcode",
         "opt",
         "lower",
-        "late deadcode",
+        "late-deadcode",
         "regalloc",
         "genssa",
     ];
@@ -503,15 +501,34 @@ window.onload = function() {
     }
 
     // Go through all columns and collapse needed phases.
-    var td = document.getElementsByTagName("td");
-    for (var i = 0; i < td.length; i++) {
-        var id = td[i].id;
-        var phase = id.substr(0, id.length-4);
-        var show = expandedDefault.indexOf(phase) !== -1
+    const td = document.getElementsByTagName("td");
+    for (let i = 0; i < td.length; i++) {
+        const id = td[i].id;
+        const phase = id.substr(0, id.length-4);
+        let show = expandedDefault.indexOf(phase) !== -1
+
+        // If show == false, check to see if this is a combined column (multiple phases).
+        // If combined, check each of the phases to see if they are in our expandedDefaults.
+        // If any are found, that entire combined column gets shown.
+        if (!show) {
+            const combined = phase.split('--+--');
+            const len = combined.length;
+            if (len > 1) {
+                for (let i = 0; i < len; i++) {
+                    if (expandedDefault.indexOf(combined[i]) !== -1) {
+                        show = true;
+                        break;
+                    }
+                }
+            }
+        }
         if (id.endsWith("-exp")) {
-            var h2 = td[i].getElementsByTagName("h2");
-            if (h2 && h2[0]) {
-                h2[0].addEventListener('click', toggler(phase));
+            const h2Els = td[i].getElementsByTagName("h2");
+            const len = h2Els.length;
+            if (len > 0) {
+                for (let i = 0; i < len; i++) {
+                    h2Els[i].addEventListener('click', toggler(phase));
+                }
             }
         } else {
             td[i].addEventListener('click', toggler(phase));
@@ -738,8 +755,16 @@ func (w *HTMLWriter) WriteFunc(phase, title string, f *Func) {
 	if w == nil {
 		return // avoid generating HTML just to discard it
 	}
-	//w.WriteColumn(phase, title, "", f.HTML())
-	w.WriteColumn(phase, title, "", f.HTML(phase, w.dot))
+	hash := hashFunc(f)
+	w.pendingPhases = append(w.pendingPhases, phase)
+	w.pendingTitles = append(w.pendingTitles, title)
+	if !bytes.Equal(hash, w.prevHash) {
+		phases := strings.Join(w.pendingPhases, "  +  ")
+		w.WriteMultiTitleColumn(phases, w.pendingTitles, fmt.Sprintf("hash-%x", hash), f.HTML(phase, w.dot))
+		w.pendingPhases = w.pendingPhases[:0]
+		w.pendingTitles = w.pendingTitles[:0]
+	}
+	w.prevHash = hash
 }
 
 // FuncLines contains source code for a function to be displayed
@@ -853,6 +878,10 @@ func (w *HTMLWriter) WriteAST(phase string, buf *bytes.Buffer) {
 // WriteColumn writes raw HTML in a column headed by title.
 // It is intended for pre- and post-compilation log output.
 func (w *HTMLWriter) WriteColumn(phase, title, class, html string) {
+	w.WriteMultiTitleColumn(phase, []string{title}, class, html)
+}
+
+func (w *HTMLWriter) WriteMultiTitleColumn(phase string, titles []string, class, html string) {
 	if w == nil {
 		return
 	}
@@ -865,9 +894,11 @@ func (w *HTMLWriter) WriteColumn(phase, title, class, html string) {
 	} else {
 		w.Printf("<td id=\"%v-exp\" class=\"%v\">", id, class)
 	}
-	w.WriteString("<h2>" + title + "</h2>")
+	for _, title := range titles {
+		w.WriteString("<h2>" + title + "</h2>")
+	}
 	w.WriteString(html)
-	w.WriteString("</td>")
+	w.WriteString("</td>\n")
 }
 
 func (w *HTMLWriter) Printf(msg string, v ...interface{}) {

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

@@ -6,6 +6,7 @@ package ssa
 
 import (
 	"bytes"
+	"crypto/sha256"
 	"fmt"
 	"io"
 )
@@ -14,6 +15,13 @@ func printFunc(f *Func) {
 	f.Logf("%s", f)
 }
 
+func hashFunc(f *Func) []byte {
+	h := sha256.New()
+	p := stringFuncPrinter{w: h}
+	fprintFunc(p, f)
+	return h.Sum(nil)
+}
+
 func (f *Func) String() string {
 	var buf bytes.Buffer
 	p := stringFuncPrinter{w: &buf}