[RFC] [modulo-sched] Change the ddg's construction

[Revital1 Eres <ERES at il dot ibm dot com>]

Hello,

This patch addresses the following argument which appeared in the
article "Changes to RTL Dataflow Analysis"
by Danny Berlin and Kenneth Zadeck (2006 GCC summit).

Currently SMS asks the data-flow analyzer to solve four
types of problems for the construction of the ddg's
inter-loop dependencies:

- Reaching defs
- Reaching uses
- Def-use chain
- Use-def chain

In the article it was claimed that asking to solve the reaching uses
problem
is expensive due to the possible large number of uses in a function and
thus
avoiding this problem should speed up the SMS pass.
In this new implementation the data-flow analyzer is been asked
to solve only two problems -
reaching defs and def-use chain.
(the use-def chain problem was also redundant)

I intend to post some statistics on the time consumed by the SMS pass
compared to the old implementation.

I would like to thank Kenneth Zadeck for his help.

Comments are welcome.

Revital

(See attached file: sms_patch)

Attachment: sms_patch
Description: Binary data