452576 - Improve CSE to recognize commutative instructions

Status: VERIFIED WONTFIX

(Tamarin Graveyard :: Tracing Virtual Machine, enhancement)

Description

[Peter Varga]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; hu; rv:1.9.0.1) Gecko/2008070208 Firefox/3.0.1
Build Identifier: tamarin-tracing/5f35ec56a98a

This patch modifies the CSE filter to be able to eliminate commutative instructions with different ordered operands. It is a small modification and does not show any measurable difference on the sunspider tests but it helps the CSE filter to remove some unnecessary instructions. In the performance tests it can eliminate 7 LIR instructions in 3 files. It is not so much, but more than nothing.

Reproducible: Always

Steps to Reproduce:
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Comment 1

[Peter Varga]

Attachment: Commutative instructions

Comment 2

[Edwin Smith]

Comment on attachment 335852 [details] [diff] [review]
Commutative instructions

Needs testing and rebasing (R-), but this is a good change that we do want so lets keep it near the top of our lists.

Comment 3

[Edwin Smith]

rebasing & testing has been done, the improvements are so minor it doesn't seem worthwhile.  reopen if a more comprehensive patch with better results comes to light.