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Global Value Numbering and dependence on SSA in GCC
- From: Kartik Singhal <kartiksinghal at gmail dot com>
- To: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Wed, 6 Feb 2013 19:53:49 +0530
- Subject: Global Value Numbering and dependence on SSA in GCC
Hi
I am an undergraduate CS student and a beginner to GCC development. I
am trying to implement a new algorithm for Global Value Numbering
proposed recently in our research group.
I have basic experience in implementing simple optimization passes as
dynamic plugins in GCC. I have some questions regarding my project,
answers to which, I believe, GCC community can help me find:
1. On going through the archives and source code, I didn't find info
on any GVN algorithm being used in GCC. Archives mention VanDrunen's
GVN-PRE, but not much about GVN in particular. Is there currently no
GVN implementation in GCC, if yes, why is that? If no, where should I
look for it?
2. I find that GCC switches to SSA form very early after CFG pass for
most of the optimizations. The algorithm that I am trying to implement
doesn't use SSA (we have found that some redundancies get skipped on
introduction of SSA). I could not find information from the GCC
Internals document or from archives on whether SSA could be skipped
altogether. Is that even possible? If not, could somebody shed some
light on how I can work with SSA representation, but ignore its
properties.
Thanks
--
Kartik
http://k4rtik.wordpress.com/