https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113576
--- Comment #16 from Richard Sandiford <rsandifo at gcc dot gnu.org> --- (In reply to Richard Biener from comment #15) > I think the problem is the cbranch pattern which looks at all of the > QImode mask - but of course it doesn't know it's really V4BImode it's > working on ... Yeah. Currently building an x86_64 toolchain to have a look, but I think whatever code uses a cbranch with a higher precision than the inputs should mask off the significant bits beforehand. cbranch can also be used for comparing two variable masks too. I suppose we could add a hook to say that padding bits of an integer mask must always be zero (and so it's expand's job to ensure that that holds for any mask operation). But it feels dangerously close to TRULY_NOOP_TRUNCATION for integers.
