[Interpreter] Add a simple dead-code elimination bytecode optimizer.

[Interpreter] Add a simple dead-code elimination bytecode optimizer.

Adds back simple dead code elimination to the bytecode pipeline.

BUG=v8:4280, chromium:616064
Committed: https://crrev.com/76368d085432aa2a919eadfe2ea01be2be50eb07
Cr-Commit-Position: refs/heads/master@{#37147}

[rmcilroy, 2016-06-06 12:21:11]

rmcilroy@chromium.org changed reviewers:
+ oth@chromium.org

[rmcilroy, 2016-06-06 12:21:12]

The perf bots seem reasonably fine with this (+/- 0.5% so in the noise, except
for arm32 Sunspider-ignition, but I don't trust that bot since the numbers are
all over the place and it thought the same for a previous change which had no
impact).

Still not super sure whether this is worth it, but it seems to cause no harm and
slightly reduces code-size, let me know what you think (I'll add unittests if
you think it's fine). Thanks.

[oth, 2016-06-06 20:36:15]

On 2016/06/06 12:21:12, rmcilroy wrote:
> The perf bots seem reasonably fine with this (+/- 0.5% so in the noise, except
> for arm32 Sunspider-ignition, but I don't trust that bot since the numbers are
> all over the place and it thought the same for a previous change which had no
> impact).
> 
> Still not super sure whether this is worth it, but it seems to cause no harm
and
> slightly reduces code-size, let me know what you think (I'll add unittests if
> you think it's fine). Thanks.

Looks great. I might run more numbers for more data, but feel we should do this.

Thanks
Orion

[rmcilroy, 2016-06-21 09:57:53]

Patchset #3 (id:40001) has been deleted

[rmcilroy, 2016-06-21 10:25:11]

Patchset #3 (id:60001) has been deleted

[rmcilroy, 2016-06-21 10:25:20]

Added tests, PTAL, thanks.

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
File test/cctest/interpreter/test-source-positions.cc (left):

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
test/cctest/interpreter/test-source-positions.cc:186: std::string function_name
= MakeFunctionName(optimization_bitmap);
It turned out this was the issue with the source positions - if the optimization
bitmap reached double digits it shifted the source positions relative to the
unoptimized case. I've just removed the suffix so both functions are the same.

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
File test/cctest/interpreter/test-source-positions.cc (right):

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
test/cctest/interpreter/test-source-positions.cc:49:
kUseFilterExpressionPositions | kUseDeadCode)                  \
Since adding all the combinations quickly becomes exponental, I decided only to
do each individual flag, each pair
of flags and all flags together - I don't think it's worth doing all the other
combinations. WDYT?

[rmcilroy, 2016-06-21 10:25:24]

The CQ bit was checked by rmcilroy@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-06-21 10:25:36]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2038083002/80001

[commit-bot: I haz the power, 2016-06-21 10:43:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-06-21 10:44:00]

Dry run: Try jobs failed on following builders:
  v8_linux64_avx2_rel_ng on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel_ng/buil...)
  v8_linux64_avx2_rel_ng_triggered on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel_ng_trig...)

[rmcilroy, 2016-06-21 10:51:37]

The CQ bit was checked by rmcilroy@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-06-21 10:51:49]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2038083002/100001

[oth, 2016-06-21 11:03:56]

Nice. lgtm.

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
File test/cctest/interpreter/test-source-positions.cc (left):

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
test/cctest/interpreter/test-source-positions.cc:186: std::string function_name
= MakeFunctionName(optimization_bitmap);
On 2016/06/21 10:25:19, rmcilroy wrote:
> It turned out this was the issue with the source positions - if the
optimization
> bitmap reached double digits it shifted the source positions relative to the
> unoptimized case. I've just removed the suffix so both functions are the same.

Ouch, mea culpa! Sorry!

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
File test/cctest/interpreter/test-source-positions.cc (right):

https://codereview.chromium.org/2038083002/diff/80001/test/cctest/interpreter...
test/cctest/interpreter/test-source-positions.cc:49:
kUseFilterExpressionPositions | kUseDeadCode)                  \
On 2016/06/21 10:25:19, rmcilroy wrote:
> Since adding all the combinations quickly becomes exponental, I decided only
to
> do each individual flag, each pair
> of flags and all flags together - I don't think it's worth doing all the other
> combinations. WDYT?

Okay here. I preferred using a counter to sweep through all combinations, but
it's a bit cryptic. The number of cases is still smallish, but agree it could be
overly conservative and doesn't scale.

[commit-bot: I haz the power, 2016-06-21 11:20:53]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-06-21 11:20:54]

Dry run: This issue passed the CQ dry run.

[rmcilroy, 2016-06-21 15:24:29]

The CQ bit was checked by rmcilroy@chromium.org

[commit-bot: I haz the power, 2016-06-21 15:24:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2038083002/100001

[commit-bot: I haz the power, 2016-06-21 15:27:00]

Committed patchset #4 (id:100001)

[commit-bot: I haz the power, 2016-06-21 15:29:34]

Description was changed from

==========
[Interpreter] Add a simple dead-code elimination bytecode optimizer.

Adds back simple dead code elimination to the bytecode pipeline.

BUG=v8:4280,chromium:616064
==========

to

==========
[Interpreter] Add a simple dead-code elimination bytecode optimizer.

Adds back simple dead code elimination to the bytecode pipeline.

BUG=v8:4280,chromium:616064

Committed: https://crrev.com/76368d085432aa2a919eadfe2ea01be2be50eb07
Cr-Commit-Position: refs/heads/master@{#37147}
==========

[commit-bot: I haz the power, 2016-06-21 15:29:35]

Patchset 4 (id:??) landed as
https://crrev.com/76368d085432aa2a919eadfe2ea01be2be50eb07
Cr-Commit-Position: refs/heads/master@{#37147}