On March 12, 2016 10:29:40 AM GMT+01:00, Jakub Jelinek <ja...@redhat.com> wrote: >On Sat, Mar 12, 2016 at 07:37:25PM +1030, Alan Modra wrote: >> > I believe Alan's point is DSE deleted the assignment to x which >can't be >> > right as long as we've left in goto *&x. >> > >> > The goto *&x should be a use of x and thus should have kept the >assignment >> > live. >> >> Right, I wasn't trying to say that ira.c:indirect_jump_optimize is >> OK. It needs the patch I posted or perhaps even better a test of >> DF_REF_INSN_INFO rather than !DF_REF_IS_ARTIFICIAL (simply because >the >> flag test is reading another field, and we need to read >> DF_REF_INSN_INFO anyway). > >Ok, that was my point. BTW, DSE isn't the only one that deletes x = 0; >cddce deletes it too. -fno-tree-dse -fno-tree-dce preserves it till >expansion.
GIMPLE_GOTO doesn't have VOPs and I don't think that we'd want VUSEs on all gotos. But just having them on indirect gotos would be inconsistent. I believe the code is undefined anyway and out of scope of a reasonable QOI. Using alloca to create/jump to code on the stack should work (we might transform that into a decl though). Richard. > Jakub
