Vector ICs: Clear the vector ic slots appropriately during debugging.

Vector ICs: Clear the vector ic slots appropriately during debugging.

When the debugger is active, a host of connected functions get an associated
DebugInfo structure, and their code is copied. The debugger uses the original
code to occasionally patch ICs with their initial value. Although IC learning
can occur, it's thrown away often, depending on the constellation of
breakpoints active or deactivating. Finally, feedback is discarded when the
debugger is turned off.

The type feedback vector needs to be brought into line with this behavior, so
now the debugger clears it's IC slots at appropriate bottlenecks in debug.cc.

R=yangguo@chromium.org
BUG=

Committed: https://crrev.com/35c3d47e88cb34e3a96ad740a43bfce36f8fd22b
Cr-Commit-Position: refs/heads/master@{#27289}

[mvstanton, 2015-03-18 16:12:51]

Hi Yang, here is the fix we discussed. Note that I'm not changing the IC
behavior because I'd prefer to keep these changes local to the debugger, and
they are adequate without introducing a new mode to the ICs.

The test is rather involved because it was difficult to prevent the debugger
from clearing ICs until after they'd gone monomorphic. That is why the
breakpoints are set up ahead of time, and why there is a "dummy" breakpoint,
never fired, only used to keep function f1 "present" to the debugger.
--Michael

[Yang, 2015-03-19 07:24:26]

On 2015/03/18 16:12:51, mvstanton wrote:
> Hi Yang, here is the fix we discussed. Note that I'm not changing the IC
> behavior because I'd prefer to keep these changes local to the debugger, and
> they are adequate without introducing a new mode to the ICs.
> 
> The test is rather involved because it was difficult to prevent the debugger
> from clearing ICs until after they'd gone monomorphic. That is why the
> breakpoints are set up ahead of time, and why there is a "dummy" breakpoint,
> never fired, only used to keep function f1 "present" to the debugger.
> --Michael

LGTM! Thanks for fixing this.

[mvstanton, 2015-03-19 07:45:21]

The CQ bit was checked by mvstanton@chromium.org

[mvstanton, 2015-03-19 07:45:22]

The patchset sent to the CQ was uploaded after l-g-t-m from yangguo@chromium.org
Link to the patchset: https://codereview.chromium.org/1014373002/#ps20001
(title: "REBASE.")

[commit-bot: I haz the power, 2015-03-19 07:45:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1014373002/20001

[commit-bot: I haz the power, 2015-03-19 08:04:01]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-19 08:04:15]

Patchset 2 (id:??) landed as
https://crrev.com/35c3d47e88cb34e3a96ad740a43bfce36f8fd22b
Cr-Commit-Position: refs/heads/master@{#27289}