On Tue, Apr 30, 2013 at 1:32 PM, Richard Biener <richard.guent...@gmail.com> wrote: > On Mon, Apr 29, 2013 at 7:34 PM, Nikhil Patil <nikhilpatil3...@gmail.com> > wrote: >> Hello, >> >> 1. Which passes of gcc make use of points-to information in >> SSA_NAME_PTR_INFO (or more precisely, pt_solution) in doing >> optimizations? > > All passes that query the alias oracle (tree-ssa-alias.h) which is almost > all passes doing optimization of memory accesses.
Thanks a lot for giving direction. I will try finding the passes. > >> >> 2. Also, who computes this points-to information and populates >> pt_solution? Is it ONLY ipa-pta pass? > > It is points-to analysis, both the IPA variant and the local variant > (ealias and alias > passes). >From what I could understand, gimple passes "pass_build_ealias" (ealias) and "pass_build_alias" (alias) flags "TODO_rebuild_alias" at end and then function "execute_function_todo" from passes.c calls "compute_may_aliases ()" which eventually computes points-to information. Then the IPA PTA pass finds a more precise points-to information. Please correct if I am wrong. > >> When I accessed pt_solution through a plugin which REPLACES ipa-pta >> pass, I found that the information (in pt_solution) with and without >> ipa-pta pass differs only in terms of flags in pt_solution. Here with >> the examples I could construct, I found that the bitmap 'vars' in >> pt_solution is same for both the cases. Is it always true? > > In theory IPA PTA should be able to compute a more precise solution, > thus have different (less) bits set in 'vars'. There are several testcases > that show this, look for ipa-pta* testcases in gcc/testsuite/ > > Richard. > >> Can someone please help in clarifying these doubts. >> >> Thanks in advance. >> >> -- >> Regards, >> Nikhil Patil. -- Regards, Nikhil Patil.
