So, would it be legitimate for extract_low_bits to query if the truncate pattern it will likely use is actually available?
Aaron Sawdey, Ph.D. saw...@linux.ibm.com IBM Linux on POWER Toolchain > On Sep 10, 2020, at 10:10 AM, Segher Boessenkool <seg...@kernel.crashing.org> > wrote: > > Hi! > > On Thu, Sep 10, 2020 at 04:33:30PM +0200, Richard Biener wrote: >> On Thu, Sep 10, 2020 at 4:22 PM Aaron Sawdey <acsaw...@linux.ibm.com> wrote: >>> If it feels like a hack, that would because it is a hack. >>> >>> What I’d really like to discuss is how to accomplish the real goal: keep >>> anything from trying to do other operations (zero/sign extend for one) to >>> POImode. >>> >>> Is there an existing mechanism for this? >> >> Not that I know, but somehow x86 gets away with OImode and XImode without >> providing too many patterns for those. > > What we were seeing is DSE (of all things!) tries to extract a DImode > from a POImode (and expects that insn to exist!) That is no good. > > > Segher
