[turbofan] Simplified lowering - introduce the concept of UseInfo.

[turbofan] Simplified lowering - introduce the concept of UseInfo.

This CL introduces a concept of UseInfo (but internally it still
uses machine types). The idea of UseInfo is to separate the concept
of truncation (what information is actually used by the user node)
and the concept of preferred representation. At the moment, the
truncation is (clumsily) represented by the type part of the
underlying machine type (UseInfo::type_).

Moreover, in this CL, we never specify the signedness of the use
because use signedness does not really make sense:
- if we care about the sign, it should be in the input's type
  (this is DCHECKed).
- if we do not care (e.g., trunctaing word32), then it should not
  be necessary. (And it is upto the user how it interprets the bits.)

Committed: https://crrev.com/e44c3238313b379910d0b535a9cefee6add7b1d4
Cr-Commit-Position: refs/heads/master@{#32110}

[Jarin, 2015-11-19 10:27:56]

Description was changed from

==========
[turbofan] Simplified lowering - introduce the concept of UseInfo.

This CL introduces a concept of UseInfo (but internally it still
uses machine types). The idea of UseInfo is to separate the concept
of truncation (what information is actually used by the user node)
and the concept of preferred representation. At the moment, the
truncation is (clumsily) represented by the type part of the
underlying machine type (UseInfo::type_).

Moreover, in this CL, we never specify the signedness of the use
because that concept does not really make sense:
- if we care about the sign, it should be in the input's type
  (this is DCHECKed).
- if we do not care (e.g., trunctaing word32), then it should not
  be necessary. (And it is upto the user how it interprets the bits.)
==========

to

==========
[turbofan] Simplified lowering - introduce the concept of UseInfo.

This CL introduces a concept of UseInfo (but internally it still
uses machine types). The idea of UseInfo is to separate the concept
of truncation (what information is actually used by the user node)
and the concept of preferred representation. At the moment, the
truncation is (clumsily) represented by the type part of the
underlying machine type (UseInfo::type_).

Moreover, in this CL, we never specify the signedness of the use
because that concept does not really make sense:
- if we care about the sign, it should be in the input's type
  (this is DCHECKed).
- if we do not care (e.g., trunctaing word32), then it should not
  be necessary. (And it is upto the user how it interprets the bits.)
==========

[Jarin, 2015-11-19 10:27:56]

jarin@chromium.org changed reviewers:
+ bmeurer@chromium.org

[Jarin, 2015-11-19 10:28:58]

Description was changed from

==========
[turbofan] Simplified lowering - introduce the concept of UseInfo.

This CL introduces a concept of UseInfo (but internally it still
uses machine types). The idea of UseInfo is to separate the concept
of truncation (what information is actually used by the user node)
and the concept of preferred representation. At the moment, the
truncation is (clumsily) represented by the type part of the
underlying machine type (UseInfo::type_).

Moreover, in this CL, we never specify the signedness of the use
because that concept does not really make sense:
- if we care about the sign, it should be in the input's type
  (this is DCHECKed).
- if we do not care (e.g., trunctaing word32), then it should not
  be necessary. (And it is upto the user how it interprets the bits.)
==========

to

==========
[turbofan] Simplified lowering - introduce the concept of UseInfo.

This CL introduces a concept of UseInfo (but internally it still
uses machine types). The idea of UseInfo is to separate the concept
of truncation (what information is actually used by the user node)
and the concept of preferred representation. At the moment, the
truncation is (clumsily) represented by the type part of the
underlying machine type (UseInfo::type_).

Moreover, in this CL, we never specify the signedness of the use
because use signedness does not really make sense:
- if we care about the sign, it should be in the input's type
  (this is DCHECKed).
- if we do not care (e.g., trunctaing word32), then it should not
  be necessary. (And it is upto the user how it interprets the bits.)
==========

[Jarin, 2015-11-19 10:29:22]

Could you take a look, please?

[Benedikt Meurer, 2015-11-19 10:38:31]

LGTM with nit

https://codereview.chromium.org/1462503005/diff/1/src/compiler/simplified-low...
File src/compiler/simplified-lowering.cc (right):

https://codereview.chromium.org/1462503005/diff/1/src/compiler/simplified-low...
src/compiler/simplified-lowering.cc:73: struct UseInfo {
Nit: class please

[Jarin, 2015-11-19 10:44:59]

https://codereview.chromium.org/1462503005/diff/1/src/compiler/simplified-low...
File src/compiler/simplified-lowering.cc (right):

https://codereview.chromium.org/1462503005/diff/1/src/compiler/simplified-low...
src/compiler/simplified-lowering.cc:73: struct UseInfo {
On 2015/11/19 10:38:31, Benedikt Meurer wrote:
> Nit: class please

Done.

[Jarin, 2015-11-19 10:45:20]

The CQ bit was checked by jarin@chromium.org

[Jarin, 2015-11-19 10:45:20]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/1462503005/#ps40001
(title: "struct -> class")

[commit-bot: I haz the power, 2015-11-19 10:45:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1462503005/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1462503005/40001

[commit-bot: I haz the power, 2015-11-19 11:09:31]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-11-19 11:10:02]

Patchset 3 (id:??) landed as
https://crrev.com/e44c3238313b379910d0b535a9cefee6add7b1d4
Cr-Commit-Position: refs/heads/master@{#32110}