Remove trivial dead stores during dead code elimination

Remove trivial dead stores during dead code elimination

Occasionally this optimizes a StringBuffer into a local string variable.  If we had targeted inlining to inline more methods on StringBuffer we would see more examples.


  padRight: function(source, $length) {
    var result, str, t1;
    result = new P.StringBuffer("");
    str = typeof source === "string" ? source : H.S(source);
    result._contents = str;
    for (t1 = str; t1.length < $length;) {
      t1 += " ";
      result._contents = t1;
    }
    return t1.charCodeAt(0) == 0 ? t1 : t1;
  },

-->

  padRight: function(source, $length) {
    var str, t1;
    str = typeof source === "string" ? source : H.S(source);
    for (t1 = str; t1.length < $length;)
      t1 += " ";
    return t1.charCodeAt(0) == 0 ? t1 : t1;
  },

R=floitsch@google.com

Committed: https://code.google.com/p/dart/source/detail?r=42302

[sra1, 2014-12-06 01:50:15]

Patchset #1 (id:1) has been deleted

[sra1, 2014-12-09 23:35:45]

sra@google.com changed reviewers:
+ herhut@google.com

[sra1, 2014-12-10 18:23:54]

Ping.

In combination with https://chromiumcodereview.appspot.com/790013002/
Uri.toString is improved:

    toString$0: function(_) {
      var sb, t1, t2, t3;
      sb = new P.StringBuffer("");
      t1 = this.scheme;
      if ("" !== t1) {
        sb.write$1(t1);
        sb.write$1(":");
      }
      t2 = this._host;
      t3 = t2 == null;
      if (!t3 || C.JSString_methods.startsWith$1(this._path, "//") || t1 ===
"file") {
        sb.write$1("//");
        t1 = this._userInfo;
        if (t1.length !== 0) {
          sb.write$1(t1);
          sb.write$1("@");
        }
        if (!t3)
          sb.write$1(t2);
        t1 = this._port;
        if (t1 != null) {
          sb.write$1(":");
          sb.write$1(t1);
        }
      }
      sb.write$1(this._path);
      t1 = this._query;
      if (t1 != null) {
        sb.write$1("?");
        sb.write$1(t1);
      }
      t1 = this._fragment;
      if (t1 != null) {
        sb.write$1("#");
        sb.write$1(t1);
      }
      t1 = sb._contents;
      return t1.charCodeAt(0) == 0 ? t1 : t1;
    },

-->

    toString$0: function(_) {
      var t1, t2, t3, t4;
      t1 = this.scheme;
      t2 = "" !== t1 ? t1 + ":" : "";
      t3 = this._host;
      t4 = t3 == null;
      if (!t4 || C.JSString_methods.startsWith$1(this._path, "//") || t1 ===
"file") {
        t1 = t2 + "//";
        t2 = this._userInfo;
        if (t2.length !== 0)
          t1 = t1 + t2 + "@";
        if (!t4)
          t1 += H.S(t3);
        t2 = this._port;
        if (t2 != null)
          t1 = t1 + ":" + H.S(t2);
      } else
        t1 = t2;
      t1 += this._path;
      t2 = this._query;
      if (t2 != null)
        t1 = t1 + "?" + H.S(t2);
      t2 = this._fragment;
      if (t2 != null)
        t1 = t1 + "#" + H.S(t2);
      return t1.charCodeAt(0) == 0 ? t1 : t1;
    },

[sra1, 2014-12-10 20:09:16]

sra@google.com changed reviewers:
+ floitsch@google.com

[floitsch, 2014-12-10 20:33:05]

LGTM.

https://chromiumcodereview.appspot.com/780403003/diff/20001/pkg/compiler/lib/...
File pkg/compiler/lib/src/ssa/optimize.dart (right):

https://chromiumcodereview.appspot.com/780403003/diff/20001/pkg/compiler/lib/...
pkg/compiler/lib/src/ssa/optimize.dart:985: Map<HInstruction, bool>
trivialDeadStoreReceivers = <HInstruction, bool>{};
Do you think a Map is warranted?
maybe just a maplet?

https://chromiumcodereview.appspot.com/780403003/diff/20001/pkg/compiler/lib/...
pkg/compiler/lib/src/ssa/optimize.dart:1032: // The use must be the receiver. 
If the use is also the argument, i.e.
Even if the use...

[sra1, 2014-12-10 23:08:48]

https://chromiumcodereview.appspot.com/780403003/diff/20001/pkg/compiler/lib/...
File pkg/compiler/lib/src/ssa/optimize.dart (right):

https://chromiumcodereview.appspot.com/780403003/diff/20001/pkg/compiler/lib/...
pkg/compiler/lib/src/ssa/optimize.dart:985: Map<HInstruction, bool>
trivialDeadStoreReceivers = <HInstruction, bool>{};
On 2014/12/10 20:33:04, floitsch wrote:
> Do you think a Map is warranted?
> maybe just a maplet?

Done.

https://chromiumcodereview.appspot.com/780403003/diff/20001/pkg/compiler/lib/...
pkg/compiler/lib/src/ssa/optimize.dart:1032: // The use must be the receiver. 
If the use is also the argument, i.e.
On 2014/12/10 20:33:04, floitsch wrote:
> Even if the use...

Done.