https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90075
--- Comment #5 from ramana.radhakrishnan at arm dot com <ramana.radhakrishnan at arm dot com> --- The main reason for the ICE is this bit of code here. GCC-8 and earlier have this bit of code in the expansion for copysignsf3 .. rtx op2 = lowpart_subreg (V2SFmode, operands[2], SFmode); .. which looks quite a bit different to the approach taken with copysigndf3 until your rewrite. This gets an input in operands[2] which is subreg:SF (reg:SI 100) and then lower_subreg->simplify_gen_subreg seems to get into a tangle that it can't get out of. That causes simplify_gen_subreg to get confused and that ends up returning a Null pointer as it is unable to do the conversion - we then don't check and thus ICE with a null pointer error. Having looked at it again this morning my reaction is that while there be dragons in subreg's of vector modes and such mode casting, the newer rewrite seems reasonable and is not papering over any underlying modes. For the release branches, I think backporting your patch (and any followups , do you remember any ?) should be fine and we should just do it ./ Ramana ________________________________________ From: rearnsha at gcc dot gnu.org <gcc-bugzi...@gcc.gnu.org> Sent: 23 April 2019 15:57 To: ram...@gcc.gnu.org Subject: [Bug middle-end/90075] [7/8 Regression] [AArch64] ICE during RTL pass when member of union passed to copysignf https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90075 --- Comment #4 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- (In reply to Ramana Radhakrishnan from comment #3) > Seems to have been "fixed" by the commit to fix PR87369, > > Richard, is this something to backport ? Prima-facie , it appears not and we > will need an appropriate fix for the release branches. Given that the patch for PR87369 eliminates the ICE, it's probably preferable for backporting to a separate patch that is only used on the release branches. That patch has now been soaking on trunk for a while now, so is likely to be pretty safe. I am a bit worried however, that the patch papers over a likely trunk ICE that isn't really fixed. It would be nice to investigate further if some additional mitigation is warranted. -- You are receiving this mail because: You are on the CC list for the bug. You are the assignee for the bug.
