On Fri, Jan 29, 2016 at 02:27:34PM +0000, Kyrill Tkachov wrote: > Hi all, > > In this PR we ICE during combine when trying to propagate a comparison into a > vec_duplicate, > that is we end up creating the rtx: > (vec_duplicate:V4SI (eq:CC_NZ (reg:CC_NZ 66 cc) > (const_int 0 [0]))) > > The documentation for vec_duplicate says: > "The output vector mode must have the same submodes as the input vector mode > or the scalar modes" > So this is invalid RTL, which triggers an assert in simplify-rtx to that > effect. > > It has been suggested on the PR that this is because we use a > special_predicate for > aarch64_comparison_operator which means that it ignores the mode when > matching. > This is fine when used in RTXes that don't need it, like if_then_else > expressions > but can cause trouble when used in places where the modes do matter, like in > SET operations. In this particular ICE the cause was the conditional store > patterns that could end up matching an intermediate rtx during combine of > (set (reg:SI) (eq:CC_NZ x y)). > > The suggested solution is to define a separate predicate with the same > conditions as aarch64_comparison_operator but make it not special, so it gets > automatic mode checks to prevent such a situation. > > This patch does that. > Bootstrapped and tested on aarch64-linux-gnu. > SPEC2006 codegen did not change with this patch, so there shouldn't be > any code quality regressions. > > Ok for trunk?
It would be good to leave a more detailed comment on "aarch64_comparison_operator_mode" as to why we need it. Otherwise, this is OK. Thanks, James > > Thanks, > Kyrill > > 2016-01-29 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > > PR target/69161 > * config/aarch64/predicates.md (aarch64_comparison_operator_mode): > New predicate. > (aarch64_comparison_operator): Break overly long line into two. > (aarch64_comparison_operation): Likewise. > * config/aarch64/aarch64.md (cstorecc4): Use > aarch64_comparison_operator_mode instead of > aarch64_comparison_operator. > (cstore<mode>4): Likewise. > (aarch64_cstore<mode>): Likewise. > (*cstoresi_insn_uxtw): Likewise. > (cstore<mode>_neg): Likewise. > (*cstoresi_neg_uxtw): Likewise. > > 2016-01-29 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > > PR target/69161 > * gcc.c-torture/compile/pr69161.c: New test.
