Original bug ID: 7450
Reporter: markghayden
Assigned to: @chambart
Status: assigned (set by @chambart on 2017-01-03T21:03:08Z)
Resolution: open
Priority: normal
Severity: feature
Platform: AMD64
OS: MacOS
OS Version: 10.12.2
Version: 4.04.0
Category: middle end (typedtree to clambda)
Tags: flambda

Bug description

Compile a file such as:

let v0 = [0;1;2;3;4;5;6;7;8;9;10;11;12;13;14;15;16;17] ;;

Then review the order of the constant blocks in the resulting assembly (attached). They appear to be in a random order, perhaps as though they were dumped from a hash table.

It is understood that with shared constant blocks the order may at times depend on the specifics of the sharing. However, it seems like a better idea would be to follow some heuristic order rather than scrambling them. with a goal to achieve better locality and cache-behavior. For instance, in this case it might be better if the order were in depth-traversal so that scanning the list resulted in reading forward through memory. Perhaps enumerating constant blocks first by file-order in which the containing block first appeared and then by depth traversal order would be simple and effective.

Steps to reproduce

Compiled with 4.05.0+flambda trunk.

File attachments

• cc.s