Add alignment to code blocks with jump tables.

Add alignment to code blocks with jump tables.

This will reduce our misaligned memory accesses.

BUG=

Committed: https://code.google.com/p/sawbuck/source/detail?r=1217

[chrisha, 2012-11-02 17:39:17]

PTAL.

[Siggi, 2012-11-02 17:47:05]

nice - lgtm!

https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc
File syzygy/pe/decomposer.cc (right):

https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc#newcode762
syzygy/pe/decomposer.cc:762: DCHECK(block != NULL);
nit: DCHECK block type for good measure?

[Roger McFarlane, 2012-11-02 17:47:26]

Sweet!

https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc
File syzygy/pe/decomposer.cc (right):

https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc#newcode774
syzygy/pe/decomposer.cc:774: // If the jump table is misaligned we can return
false immediately.
if _a_ jump table

If there a multiple jump tables with differing alignment, do we want to preserve
their original alignnment.

Similarly, I would think we would want to preserve case table alighment as well.
For example, if I'm indexing into 32-bit case table data, I would presumably
want that to remain aligned as well.

[Roger McFarlane, 2012-11-02 17:50:00]

Otherwise, LGTM


On Fri, Nov 2, 2012 at 1:47 PM, <rogerm@chromium.org> wrote:

> Sweet!
>
>
>
>
https://codereview.appspot.**com/6811072/diff/1/syzygy/pe/**decomposer.cc<htt...
> File syzygy/pe/decomposer.cc (right):
>
> https://codereview.appspot.**com/6811072/diff/1/syzygy/pe/**
>
decomposer.cc#newcode774<https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc#newcode774>
> syzygy/pe/decomposer.cc:774: // If the jump table is misaligned we can
> return false immediately.
> if _a_ jump table
>
> If there a multiple jump tables with differing alignment, do we want to
> preserve their original alignnment.
>
> Similarly, I would think we would want to preserve case table alighment
> as well. For example, if I'm indexing into 32-bit case table data, I
> would presumably want that to remain aligned as well.
>
>
https://codereview.appspot.**com/6811072/<https://codereview.appspot.com/6811...
>

[chrisha, 2012-11-02 17:51:00]

Thanks, committing.

https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc
File syzygy/pe/decomposer.cc (right):

https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc#newcode762
syzygy/pe/decomposer.cc:762: DCHECK(block != NULL);
On 2012/11/02 17:47:05, Siggi wrote:
> nit: DCHECK block type for good measure?

Done.

https://codereview.appspot.com/6811072/diff/1/syzygy/pe/decomposer.cc#newcode774
syzygy/pe/decomposer.cc:774: // If the jump table is misaligned we can return
false immediately.
On 2012/11/02 17:47:26, Roger McFarlane wrote:
> if _a_ jump table

Done.

> If there a multiple jump tables with differing alignment, do we want to
preserve
> their original alignnment.
> 
> Similarly, I would think we would want to preserve case table alighment as
well.
> For example, if I'm indexing into 32-bit case table data, I would presumably
> want that to remain aligned as well.

If they have differing alignment, there's something weird going on and I simply
pass. As to case tables, we don't know anything about the size of their contents
and you never see a case table without a jump table, so their alignments will be
preserved as a side effect.