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LNO Branch merge proposal
- From: David Edelsohn <dje at watson dot ibm dot com>
- To: gcc at gcc dot gnu dot org
- Date: Wed, 17 Mar 2004 14:23:09 -0500
- Subject: LNO Branch merge proposal
The developers of the LNO Branch, with support from Apple
Computer, Inc., IBM Corporation, and SUSE, plan to contribute the branch
for merger into mainline shortly after Tree-SSA is merged into mainline.
We suggest one to three weeks after Tree-SSA is merged to allow for settling
of that merge.
As with Tree-SSA, the new functions and options will be well
documented and we request code reviews and feedback for all components of
the branch.
The proposed testing requirement is that LNO branch will show no
testsuite regressions with respect to mainline (after the Tree-SSA merge)
for the same targets specified for the Tree-SSA merge.
The new features are considered a technology preview. We do not
propose enabling the new functionality at any default -O optimization
level in GCC until a more thorough cost-benefit analysis has been
performed. This is an implicit commitment that merging LNO will not
affect compilation speed when LNO options remain disabled.
Testing of the branch shows performance improvements and many
developers are eager to have LNO available to begin to show the full
performance potential of Tree-SSA. However, for the next GCC release,
correctness will be the focus of the code on mainline. We will address
any ICEs and wrong-code reported by users invoking LNO optimizations.