Improve positions tracking inside the HGraphBuilder.

Improve positions tracking inside the HGraphBuilder.

Instead of tracking simple absolute offset from the start of the script like other places do, track a pair of (inlining id, offset from the start of inlined function).

This enables us to pinpoint with inlining path an instruction came from. Previously in multi-script environments we emitted positions that made very little sense because inside a single optimized function they would point to different scripts without a way to distinguish them.

Start dumping the source of every inlined function to make possible IR viewing tools with integrated source views as there was previously no way to acquire this information from IR dumps. We also dump source position at which each inlining occured.

Tracked positions are written into hydrogen.cfg as pos:<inlining-id>_<offset>.

Flag --emit-opt-code-positions is renamed by this change into --hydrogen-track-positions to better convey it's meaning.

In addition this change assigned global unique identifier to each optimization performed inside isolate. This allows to precisely match compilation artifacts (e.g. IR and disassembly) and deoptimizations.

BUG=
R=yangguo@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=19360

[Vyacheslav Egorov (Chromium), 2014-01-29 16:41:36]

(cc rstrurgell fyi)

Hi Daniel!

This is the CL explores some of the improvements in our IR dumps that we touched
some time ago. 

Main motivation behind it is that it enables building very user friendly
IR/deopt viewers. Checkout the demo: http://www.youtube.com/watch?v=pycQWDuCBN8

https://codereview.chromium.org/140683011/diff/1/src/objects.h
File src/objects.h (right):

https://codereview.chromium.org/140683011/diff/1/src/objects.h#newcode4941
src/objects.h:4941: static const int kOptimizationIdIndex = 5;
Rest of the change introduces no overhead unless FLAG_track_hydrogen_positions
is passed. This part however grows DeoptimizationInputData by one word to store
ID of the optimization.

In general DeoptimizationInputData is big and is also accompanied by a multiword
optimized code object so this overhead should not be noticable. 

However if we want to save space we can change encoding of this structure to be
more flexible. If we decide to pursue this as additional benefit of such action
we can remove OsrAstId and OsrPcOffset for many object (my guess they are not
used for many objects) and save 2 words.

[Vyacheslav Egorov (Chromium), 2014-02-03 14:17:00]

Adding Yang as a reviewer per Danno's suggestion.

[Vyacheslav Egorov (Google), 2014-02-10 12:25:13]

ping. don't want this CL to rot :)

[Yang, 2014-02-12 17:32:05]

LGTM with comments.

https://codereview.chromium.org/140683011/diff/1/src/hydrogen-instructions.h
File src/hydrogen-instructions.h (right):

https://codereview.chromium.org/140683011/diff/1/src/hydrogen-instructions.h#...
src/hydrogen-instructions.h:1170: // TODO(vegorov): what we really want to track
here is a combination of
Is this still a TODO?

https://codereview.chromium.org/140683011/diff/1/src/hydrogen-instructions.h#...
src/hydrogen-instructions.h:1250: const intptr_t result = (val <<
kPositionShift) | kPositionTag;
The way the bit fields in HSourcePosition are defined, all of the 32 bits are
used. So on a 32-bit platform, won't we lose the most significant bit through
tagging?

https://codereview.chromium.org/140683011/diff/1/src/hydrogen.h
File src/hydrogen.h (right):

https://codereview.chromium.org/140683011/diff/1/src/hydrogen.h#newcode2091
src/hydrogen.h:2091: function_state_ = state;
stray edit?

[Vyacheslav Egorov (Chromium), 2014-02-13 16:09:45]

Committed patchset #2 manually as r19360 (presubmit successful).

[Vyacheslav Egorov (Chromium), 2014-02-13 16:17:42]

Thanks for the review. Landed.

https://codereview.chromium.org/140683011/diff/1/src/hydrogen-instructions.h
File src/hydrogen-instructions.h (right):

https://codereview.chromium.org/140683011/diff/1/src/hydrogen-instructions.h#...
src/hydrogen-instructions.h:1170: // TODO(vegorov): what we really want to track
here is a combination of
On 2014/02/12 17:32:06, Yang wrote:
> Is this still a TODO?

Done.

https://codereview.chromium.org/140683011/diff/1/src/hydrogen-instructions.h#...
src/hydrogen-instructions.h:1250: const intptr_t result = (val <<
kPositionShift) | kPositionTag;
Good catch!

I was using 31 bits originally to avoid loosing any, but then I was cleaning up
some code and ended up with 32 bits in HSourcePosition. I will fix it.

https://codereview.chromium.org/140683011/diff/1/src/hydrogen.h
File src/hydrogen.h (right):

https://codereview.chromium.org/140683011/diff/1/src/hydrogen.h#newcode2091
src/hydrogen.h:2091: function_state_ = state;
On 2014/02/12 17:32:06, Yang wrote:
> stray edit?

Done.