https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63783
--- Comment #21 from Oleg Endo <olegendo at gcc dot gnu.org> --- (In reply to Michael Karcher from comment #20) > Of course. The instructions involving src_reg in make_not_reg_insn dealing > with src_reg are completely quoted here: > > + // On SH we can do only SImode and DImode comparisons. > + if (! (GET_MODE (src_reg) == SImode || GET_MODE (src_reg) == DImode)) > + return NULL; > > In this fragment, you accept DImode source operands. So that code may be > used to replace a DImode compare. > > + emit_insn (gen_rtx_SET (VOIDmode, m_ccreg, > + gen_rtx_fmt_ee (EQ, SImode, src_reg, const0_rtx))); > > In this fragment, you are generating the replacement instruction, which is > always an SImode compare. Maybe I miss the point, but I fail to undestand > how an SImode compare might be acceptable on an DImode operand. Possibly, > this even ICEs, I don't know enough about gcc internals to know what happens > if src_reg is DImode which is passed to EQ in SImode. The SImode refers to the result of the EQ, not the operands. In sh.md the pattern cmpeqdi_t will be picked up for this.