> On Oct 3, 2018, at 4:04 AM, Jan Hubicka <hubicka@xxxxxx> wrote: > >> >> That was promised to be done by Honza Hubička. He's very skilled in IPA optimizations and he's aware >> of optimizations that cause troubles for live-patching. > > :) I am not sure how skilful I am, but here is what I arrived to. > > We have transformations that are modeled as clonning, which are > - inlining (can't be disabled completely because of always inline, but -fno-inline > does most of stuff) > - cloning (disabled via -fno-ipa-cp) > - ipa-sra (-fno-ipa-sra) > - splitting (-fno-partial-inlining) > These should play well with Martin's tracking code In addition to the above IPA transformations that cloned a routine, the following RTL transformation will clone a routine, too: reorder-blocks-and-partition this optimization will create .cold routines based on profiling feedback. looks like that we also need to include this transformation into this category? > > We propagate info about side effects of function: > - function attribute discovery (pure, const, nothrow, malloc) > Some of this can be disabled by -fno-ipa-pure-const, but not all > of it. Nothrow does not have flag but it is obviously not a concern > for C++ > - ipa-pta (disabled by default, -fno-ipa-pta) > - ipa-reference (list of accessed/modified global vars), disable by -fno-ipa-refernece > - stack alignment requirements (no flag to disable) > - inter-procedural register allocation (-fno-ipa-ra) > > We perform discovery of functions/variables with no address taken and > optimizations that are not valid otherwise such as duplicating them > or doing skipping them for alias analysis (no flag to disable) > > Identical code folding merges function bodies that are semanticaly equivalent > and thus one can't patch one without patching another, -fno-ipa-icf > > Unreachable code/variable removal may be concern too (no flag to disable) > > Write only global variable discovery (no flag to dosable) > > Visibility changes with -flto and/or -fwhole-program > > We also have profile propagation (discovery of cuntions used only in cold regions, > but that I guess is only performance issue not correctness) > No flag to disable are all the above analyzes guarded by AVAIL_INTERPOSABLE right now? If NOT, should they be guarded by AVAIL_INTERPOSABLE? Qing > > Honza > >> >> Martin >> >>> >>> thanks. >>> >>> Qing >>> >>
