Avoid array bounds check when allowed by guarded field.

Avoid array bounds check when allowed by guarded field.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=26604

[srdjan, 2013-08-22 22:02:42]

https://codereview.chromium.org/23003026/diff/1/runtime/vm/intermediate_langu...
File runtime/vm/intermediate_language_arm.cc (right):

https://codereview.chromium.org/23003026/diff/1/runtime/vm/intermediate_langu...
runtime/vm/intermediate_language_arm.cc:4328: intptr_t guarded_array_length =
-1;
Instead of checking here, move the code to CheckArrayBoundInstr::Canonicalize to
eliminated redundant bounds checks.

[Cutch, 2013-08-22 22:51:32]

On 2013/08/22 22:02:42, srdjan wrote:
>
https://codereview.chromium.org/23003026/diff/1/runtime/vm/intermediate_langu...
> File runtime/vm/intermediate_language_arm.cc (right):
> 
>
https://codereview.chromium.org/23003026/diff/1/runtime/vm/intermediate_langu...
> runtime/vm/intermediate_language_arm.cc:4328: intptr_t guarded_array_length =
> -1;
> Instead of checking here, move the code to CheckArrayBoundInstr::Canonicalize
to
> eliminated redundant bounds checks.

PTAL.

[srdjan, 2013-08-22 22:56:18]

lgtm

[Florian Schneider, 2013-08-23 08:26:15]

dbc:

https://codereview.chromium.org/23003026/diff/6001/runtime/vm/flow_graph_opti...
File runtime/vm/flow_graph_optimizer.cc (right):

https://codereview.chromium.org/23003026/diff/6001/runtime/vm/flow_graph_opti...
runtime/vm/flow_graph_optimizer.cc:789: if (i->IsConstant() &&
guarded_array_length >= 0) {
When done here, it works only for constant index expressions.
But if you eliminate the bounds check after range analysis, there will be more
opportunities for non-constant index where the range is known.

[Cutch, 2013-08-23 17:48:31]

Committed patchset #2 manually as r26604 (presubmit successful).

[Cutch, 2013-08-23 17:48:40]

On 2013/08/23 08:26:15, Florian Schneider wrote:
> dbc:
> 
>
https://codereview.chromium.org/23003026/diff/6001/runtime/vm/flow_graph_opti...
> File runtime/vm/flow_graph_optimizer.cc (right):
> 
>
https://codereview.chromium.org/23003026/diff/6001/runtime/vm/flow_graph_opti...
> runtime/vm/flow_graph_optimizer.cc:789: if (i->IsConstant() &&
> guarded_array_length >= 0) {
> When done here, it works only for constant index expressions.
> But if you eliminate the bounds check after range analysis, there will be more
> opportunities for non-constant index where the range is known.

Hi Florian,

I will be in AAR next week. Let's discuss how to extend what I have with your
idea.