Reduce SharedFunctionInfo size.

Reduce SharedFunctionInfo size.

The API function data and the debug info fields are never used at the same
time, as API functions are not debuggable. We can share a field.

R=jkummerow@chromium.org

[Yang, 2015-07-22 12:18:51]

On 2015/07/22 12:17:34, Yang wrote:

That saves a word per SFI, so for an new isolate, this is about 9K memory saved.

[Jakob Kummerow, 2015-07-22 12:24:03]

Yay! But I'd like to harden this a bit if possible. Field sharing is dangerous
business.

https://codereview.chromium.org/1252473002/diff/1/src/objects-inl.h
File src/objects-inl.h (right):

https://codereview.chromium.org/1252473002/diff/1/src/objects-inl.h#newcode5479
src/objects-inl.h:5479: bool has_debug_info = !IsApiFunction() &&
debug_info()->IsStruct();
I can haz DCHECK(!IsApiFunction()) inside debug_info()? That probably requires
adding checks at other call sites, but would let me sleep better.

[Michael Starzinger, 2015-07-22 12:33:25]

mstarzinger@chromium.org changed reviewers:
+ mstarzinger@chromium.org

[Michael Starzinger, 2015-07-22 12:33:25]

Aehm, not so fast, are you aware of this CL:
https://codereview.chromium.org/1230753004/

[Yang, 2015-07-22 12:38:26]

On 2015/07/22 12:33:25, Michael Starzinger wrote:
> Aehm, not so fast, are you aware of this CL:
> https://codereview.chromium.org/1230753004/

Thanks! I was not. I'll close this CL then.