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DONT_BREAK_DEPENDENCIES bitmask for scheduling

From: "Paulo Matos" <pmatos at broadcom dot com>
To: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
Date: Mon, 1 Jul 2013 16:31:44 +0000
Subject: DONT_BREAK_DEPENDENCIES bitmask for scheduling

Hi,

Near the start of schedule_block, find_modifiable_mems is called if DONT_BREAK_DEPENDENCIES is not enabled for this scheduling pass. It seems on c6x backend currently uses this.
However, it's quite strange that this is not a requirement for all backends since find_modifiable_mems, moves all my dependencies in SD_LIST_HARD_BACK to SD_LIST_SPEC_BACK even though I don't have DO_SPECULATION enabled.

Since dependencies are accessed later on from try_ready (for example), I would have thought that it would be always good not to call find_modifiable_mems,  given that it seems to 'literally' break dependencies.

Is the behaviour of find_modifiable_mems a bug or somehow expected?

Cheers,

Paulo Matos

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