Correct bailout from TurboFan for unsupported targets.

Correct bailout from TurboFan for unsupported targets.

R=titzer@chromium.org
TEST=mjsunit/asm/math-fround

Committed: https://code.google.com/p/v8/source/detail?r=24232

[Michael Starzinger, 2014-09-25 10:51:32]

This is a follow-up to a comment on another CL:
https://codereview.chromium.org/594183004/

[titzer, 2014-09-25 11:25:15]

Does this mean that TypedLowering cannot run on non-supported platforms because
of the builtin reducer (in turn because of Linkage?). If that's the case, then
that should get better when we split linkage.

But until then can we make the builtin reducer do nothing if it's not a
supported target?

[Michael Starzinger, 2014-09-25 12:52:09]

On 2014/09/25 11:25:15, titzer wrote:
> Does this mean that TypedLowering cannot run on non-supported platforms
because
> of the builtin reducer (in turn because of Linkage?). If that's the case, then
> that should get better when we split linkage.
> 
> But until then can we make the builtin reducer do nothing if it's not a
> supported target?

Almost ... it means that TypedLowering cannot run on non-supported platforms
because of the ChangeLowering (in turn because of Linkage?). This is the
completely unrelated to the builtin reducer. This is also the reason why the
typed pipeline is still turned off (see the #ifdef in flag-definitions.h). I am
happy to work on this, but this is nothing new, we never ran the typed pipeline
on non-supported platforms, it was just well hidden. We don't loose coverage at
all with this change, we just make it explicit. :)

[titzer, 2014-09-25 14:23:53]

On 2014/09/25 12:52:09, Michael Starzinger wrote:
> On 2014/09/25 11:25:15, titzer wrote:
> > Does this mean that TypedLowering cannot run on non-supported platforms
> because
> > of the builtin reducer (in turn because of Linkage?). If that's the case,
then
> > that should get better when we split linkage.
> > 
> > But until then can we make the builtin reducer do nothing if it's not a
> > supported target?
> 
> Almost ... it means that TypedLowering cannot run on non-supported platforms
> because of the ChangeLowering (in turn because of Linkage?). This is the
> completely unrelated to the builtin reducer. This is also the reason why the
> typed pipeline is still turned off (see the #ifdef in flag-definitions.h). I
am
> happy to work on this, but this is nothing new, we never ran the typed
pipeline
> on non-supported platforms, it was just well hidden. We don't loose coverage
at
> all with this change, we just make it explicit. :)

LGTM

Got it.

[Michael Starzinger, 2014-09-25 15:26:12]

Committed patchset #1 (id:1) manually as 24232 (tree was closed).