questions about dependence analysis in CG

[Ian Lance Taylor]

Peng Zhao <blue_3too@hotmail.com> writes:

> 1. what is the purpose of the reg_note and ds_t?

The reg-note lives in the RTL.  ds_t is the same information represented
as a bitflag.  E.g., see how the bits are accumulated in a ds_t variable
in ask_dependency_caches.

> Where can I find information about memory dependences such as a write
> and read on elementa[100] ? Sometimes meory dependence should be
> handled differenly with reg dependece in CG, such as the latency
> between the producer and the consumer.

The reg-notes do handle some memory dependencies.  Also, see
true_dependence and friends in alias.c.  Richard Guenther probably has a
better answer.

> 2. What different purpose are haifa_note_mem_dep and haifa_note_dep for?

To add a memory dependency.

Ian