[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 Richard Biener changed: What|Removed |Added Priority|P3 |P2
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #13 from hubicka at kam dot mff.cuni.cz --- > Result pure looping 0 > Function found to be pure: foo/4 This is good - we are supposed to find it to be pure and walk all aliases and update noninterposable ones > Declaration updated to be pure: foo/4 I have to take look why this happens though.
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #12 from Andrew Pinski --- (In reply to Rich Felker from comment #11) > Are you sure? If pure/const discovery is no longer applied to weak > definitions, it shouldn't be able to propagate to a non-inlined caller. Of > course the fix may be incomplete or not working, which I guess we could tell > from whether it happened prior to or after comment 5. :) There still looks like there is a bug as shown by taking the original testcase in comment #0 and using -O2 -fno-inline, you will get: reclaim_gaps: ret ... foo: ret Which is still wrong as reclaim should not be considered as pure. >From *.pure-const: Starting cycle Visiting donate_dummy/0 state:const looping 0 Result const looping 0 Function found not to call free: donate_dummy/0 Starting cycle Visiting reclaim/2 state:pure looping 0 Call to __malloc_donate/1 const Result pure looping 0 Function found to be pure: reclaim/2 Declaration updated to be pure: reclaim/2 Starting cycle Visiting reclaim_gaps/3 state:pure looping 0 Call to reclaim/2 state:pure looping:0 Call to reclaim/2 state:pure looping:0 Result pure looping 0 Function found to be pure: reclaim_gaps/3 Declaration updated to be pure: reclaim_gaps/3 Starting cycle Visiting foo/4 state:const looping 0 Call to reclaim_gaps/3 state:pure looping:0 Result pure looping 0 Function found to be pure: foo/4 Declaration updated to be pure: foo/4 reclaim, reclaim_gaps and foo are all found as pure. without -fno-inline, we get some early inlining which causes the difference there.
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #11 from Rich Felker --- Are you sure? If pure/const discovery is no longer applied to weak definitions, it shouldn't be able to propagate to a non-inlined caller. Of course the fix may be incomplete or not working, which I guess we could tell from whether it happened prior to or after comment 5. :)
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #10 from Alexander Monakov --- As comment #5 mentioned, it is still broken, you just need -fno-inline in addition to -O2 for the original testcase. Andrew's remark is quite useful for situations like this, you know :)
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #9 from Rich Felker --- Can you provide a link to the commit that might have fixed it? I imagine it's simple enough to backport, in which case I'd like to do so.
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #8 from hubicka at kam dot mff.cuni.cz --- > > Do weak aliases fall under some implicit ODR here? > > The whole definition of "weak" is that it entitles you to make a definition > that will be exempt from ODR, where a non-weak definition, if any, replaces > it. I fixed recently bug in pure-const discovery which made us to add attributes to weaks while it should not, so perhaps this bug is gone. For non-inline functions we should handle those as interposable. Concerning warning, I we make difference between may and must warnings. I think this is still useful do be diagnosed for user to consider (perhaps there is a reason why all overwritters has to be weak), so I think we should porduce may form of warning. I will take a look.
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #7 from Rich Felker --- > Do weak aliases fall under some implicit ODR here? The whole definition of "weak" is that it entitles you to make a definition that will be exempt from ODR, where a non-weak definition, if any, replaces it.
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 --- Comment #6 from Richard Biener --- Honza? What's your stance here? Do weak aliases fall under some implicit ODR here?
[Bug ipa/95558] [9/10/11/12 Regression] Invalid IPA optimizations based on weak definition
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95558 Andrew Pinski changed: What|Removed |Added Known to fail||4.7.1 Known to work||4.5.3, 4.6.4 Target Milestone|--- |9.5 Summary|Invalid IPA optimizations |[9/10/11/12 Regression] |based on weak definition|Invalid IPA optimizations ||based on weak definition --- Comment #5 from Andrew Pinski --- Note you need -fno-inline to produce the issue these days. Plus it is a regression from GCC 4.6.
