Better end of loop counter optimisation

Registered by Michael Hope on 2012-03-20

GCC can calculate the final value of a loop counter and use that in later optimisations. The value is calculated in the original signed type which, due to overflow rules, can lead to a strange looking value which is not supported and reduced by later optimisations.

Improve either through reducing the calculated value or implementing or improving later passes.

See:
 http://gcc.gnu.org/ml/gcc/2012-02/msg00371.html

Blueprint information

Status:
Complete
Approver:
Michael Hope
Priority:
High
Drafter:
Michael Hope
Direction:
Approved
Assignee:
Kugan Vivekanandarajah
Definition:
Approved
Series goal:
Accepted for 4.7
Implementation:
Informational Informational
Milestone target:
milestone icon backlog
Started by
Michael Hope on 2012-03-20
Completed by
Matthew Gretton-Dann on 2013-05-21

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[2013-05-21 matthew-gretton-dann] Moved to TCWG-57: http://cards.linaro.org/browse/TCWG-57

Status: upstream wants a different implementation. Parked.

Do as a plus/minus reassociation pass.

(?)

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