On Wed, Feb 6, 2013 at 3:23 PM, Kartik Singhal <kartiksing...@gmail.com> wrote: > 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?
PRE is based on GVN-PRE but the GVN part was exchanged for a SCC based VN (tree-ssa-sccvn.c) at some point (Cooper & Simpson). > 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. Well, to ignore SSA form simply treat each SSA name as separate variable. You of course need to handle PHI nodes as copies on CFG edges then. Richard. > > Thanks > -- > Kartik > http://k4rtik.wordpress.com/
