Improvement to SsaLoadElimination

Improvement to SsaLoadElimination

nonEscapingReceivers was always empty at the top of a loop, making
scalar replacement candidates susceptible to spurious may-alias
invalidations.

R=het@google.com

Committed: https://github.com/dart-lang/sdk/commit/646af36e933f9dbc65d0000e092645e7f6d1e7e9

[sra1, 2016-10-04 20:57:48]

Patchset #1 (id:1) has been deleted

[sra1, 2016-10-04 21:07:37]

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

[sra1, 2016-10-04 21:07:37]

This fixes some of the failed scalar replacements of StringBuffer that have been
bothering me.

Example: IterableMixin.join:

      join$1: function(_, separator) {
        var iterator, buffer, t1;
        iterator = this.get$iterator(this);
        if (!iterator.moveNext$0())
          return "";
        buffer = new P.StringBuffer("");
        if (separator == null || separator === "") {
          do
            buffer._contents += H.S(iterator.get$current());
          while (iterator.moveNext$0());
        } else {
          buffer._contents = H.S(iterator.get$current());
          for (; iterator.moveNext$0();) {
            buffer._contents += H.S(separator);
            buffer._contents += H.S(iterator.get$current());
          }
        }
        t1 = buffer._contents;
        return t1.charCodeAt(0) == 0 ? t1 : t1;
      },

--->

      join$1: function(_, separator) {
        var iterator, t1;
        iterator = this.get$iterator(this);
        if (!iterator.moveNext$0())
          return "";
        if (separator == null || separator === "") {
          t1 = "";
          do
            t1 += H.S(iterator.get$current());
          while (iterator.moveNext$0());
        } else {
          t1 = H.S(iterator.get$current());
          for (; iterator.moveNext$0();)
            t1 = t1 + H.S(separator) + H.S(iterator.get$current());
        }
        return t1.charCodeAt(0) == 0 ? t1 : t1;
      },

[Harry Terkelsen, 2016-10-05 16:03:12]

lgtm

[sra1, 2016-10-05 17:03:35]

Description was changed from

==========
Improvement to SsaLoadElimination

nonEscapingReceivers was always empty at the top of a loop, making
scalar replacement candidates susceptible to spurious may-alias
invalidations.
==========

to

==========
Improvement to SsaLoadElimination

nonEscapingReceivers was always empty at the top of a loop, making
scalar replacement candidates susceptible to spurious may-alias
invalidations.

R=het@google.com

Committed:
https://github.com/dart-lang/sdk/commit/646af36e933f9dbc65d0000e092645e7f6d1e7e9
==========

[sra1, 2016-10-05 17:03:35]

Committed patchset #2 (id:40001) manually as
646af36e933f9dbc65d0000e092645e7f6d1e7e9 (presubmit successful).