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From "Matthias Boehm (JIRA)" <>
Subject [jira] [Closed] (SYSTEMML-1935) Improve rewrite for merging statement blocks
Date Thu, 30 Nov 2017 22:21:00 GMT


Matthias Boehm closed SYSTEMML-1935.
       Resolution: Done
         Assignee: Matthias Boehm
    Fix Version/s: SystemML 1.0

> Improve rewrite for merging statement blocks
> --------------------------------------------
>                 Key: SYSTEMML-1935
>                 URL:
>             Project: SystemML
>          Issue Type: Task
>            Reporter: Matthias Boehm
>            Assignee: Matthias Boehm
>             Fix For: SystemML 1.0
> There are two shortcomings of the (recently introduced) rewrite on merging statement
block sequences.
> * Order of statement block rewrites: Currently, we apply HOP DAG rewrites and statement
block rewrites recursively over the entire program. For statement block rewrites, we first
apply sequence rewrites and then individual block rewrites. However, this misses opportunities
when an individual block rewrite such as branch-removal expands for example an if to a sequence
of blocks. 
> * Missing dead code elimination: When merging statement blocks, we connect transient
writes and transient reads and add roots if they are not existing transient writes. However,
we should explicitly check the live out set in order to eliminate dead code that does not
need to be computed (e.g., originating from branch-removal and sequence merge)

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