A64: Make branch to deferred code in StringCharFromCode longer.

A64: Make branch to deferred code in StringCharFromCode longer.

TEST=mjsunit/md5
R=rodolph.perfetta@arm.com

Committed: https://code.google.com/p/v8/source/detail?r=18980

[ulan, 2014-01-30 18:28:40]

Please take a look. In the long term we probably need more general solution for
this type of problem.

I've been thinking about handling it in masm:

When we emit a branch instruction, check if the target label is bound. If it is
bound, then we know the distance and can emit the correct branch instruction.
Otherwise, emit the requested branch instruction + nop, so that later on we
could change it to a longer jump if the label is bound too far away.

Another approach is to add NEAR/FAR parameter to branch instructions like in
x64.

[Rodolph Perfetta (ARM), 2014-01-30 19:27:55]

On 2014/01/30 18:28:40, ulan wrote:
> Please take a look. In the long term we probably need more general solution
for
> this type of problem.
> 
> I've been thinking about handling it in masm:
> 
> When we emit a branch instruction, check if the target label is bound. If it
is
> bound, then we know the distance and can emit the correct branch instruction.
> Otherwise, emit the requested branch instruction + nop, so that later on we
> could change it to a longer jump if the label is bound too far away.
> 
> Another approach is to add NEAR/FAR parameter to branch instructions like in
> x64.

We are working on a generic fix. Current preference is not to use Near/Far, we
are evaluating alternatives (adding nop, using veneer). Probably easier to
discuss offline.

[Rodolph Perfetta (ARM), 2014-01-30 19:28:00]

lgtm

[ulan, 2014-01-31 10:07:53]

Committed patchset #1 manually as r18980 (presubmit successful).