Debugger: make debug code on-stack replacement more robust.

Debugger: make debug code on-stack replacement more robust.

The new implemtation counts the number of calls (or continuations)
before the PC to find the corresponding PC in the new code.

R=mstarzinger@chromium.org
BUG=chromium:507070
LOG=N

Committed: https://crrev.com/dec11f5ee00a3ef1af8984d316aa98b3dee3a348
Cr-Commit-Position: refs/heads/master@{#29636}

[Yang, 2015-07-10 22:46:36]

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

[commit-bot: I haz the power, 2015-07-10 22:46:54]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1235603002/20001

[commit-bot: I haz the power, 2015-07-10 23:11:14]

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

[commit-bot: I haz the power, 2015-07-10 23:11:15]

Dry run: Try jobs failed on following builders:
  v8_linux_arm64_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_arm64_rel/builds/7547)

[Yang, 2015-07-13 06:54:58]

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

[commit-bot: I haz the power, 2015-07-13 06:55:02]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1235603002/30001

[commit-bot: I haz the power, 2015-07-13 07:32:56]

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

[commit-bot: I haz the power, 2015-07-13 07:32:58]

Dry run: This issue passed the CQ dry run.

[Yang, 2015-07-13 11:44:19]

On 2015/07/13 07:32:58, commit-bot: I haz the power wrote:
> Dry run: This issue passed the CQ dry run.

ping

[Michael Starzinger, 2015-07-13 19:35:24]

LGTM.

https://codereview.chromium.org/1235603002/diff/30001/src/debug.cc
File src/debug.cc (right):

https://codereview.chromium.org/1235603002/diff/30001/src/debug.cc#newcode1452
src/debug.cc:1452: delta = old_pc - current_pc;
This assumes that for each call site the size is the same in debug as well as in
non-debug code. Does this hold?

[Yang, 2015-07-14 05:49:19]

On 2015/07/13 19:35:24, Michael Starzinger wrote:
> LGTM.
> 
> https://codereview.chromium.org/1235603002/diff/30001/src/debug.cc
> File src/debug.cc (right):
> 
> https://codereview.chromium.org/1235603002/diff/30001/src/debug.cc#newcode1452
> src/debug.cc:1452: delta = old_pc - current_pc;
> This assumes that for each call site the size is the same in debug as well as
in
> non-debug code. Does this hold?

That holds. The call site in debug code is the same as in non-debug code. The
only difference is that the debug code contains a debug break slot *before* the
call. I calculate the delta so that I don't have to introduce a call instruction
length constant for each platform.

[Yang, 2015-07-14 05:49:24]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-07-14 05:49:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1235603002/30001

[commit-bot: I haz the power, 2015-07-14 05:51:24]

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

[commit-bot: I haz the power, 2015-07-14 05:51:25]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/4165)

[Yang, 2015-07-14 06:09:44]

The CQ bit was checked by yangguo@chromium.org

[Yang, 2015-07-14 06:09:44]

The patchset sent to the CQ was uploaded after l-g-t-m from
mstarzinger@chromium.org
Link to the patchset: https://codereview.chromium.org/1235603002/#ps50001
(title: "rebase")

[commit-bot: I haz the power, 2015-07-14 06:09:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1235603002/50001

[commit-bot: I haz the power, 2015-07-14 06:38:48]

Committed patchset #4 (id:50001)

[commit-bot: I haz the power, 2015-07-14 06:39:05]

Patchset 4 (id:??) landed as
https://crrev.com/dec11f5ee00a3ef1af8984d316aa98b3dee3a348
Cr-Commit-Position: refs/heads/master@{#29636}