https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88778
--- Comment #4 from 刘袋鼠 <crazylht at gmail dot com> --- Currently _Complex is classified as SSE_REG_CLASS, and need two 2 hardreg to handle it. We may need to handle things like TARGET_HARD_REGNO_MODE_OK in backend. So that ira can work suitable for our complex operation. static int classify_argument (machine_mode mode, const_tree type, enum x86_64_reg_class classes[MAX_CLASSES], int bit_offset) ... case E_SCmode: classes[0] = X86_64_SSE_CLASS; ... static unsigned int ix86_hard_regno_nregs (unsigned int regno, machine_mode mode) { ... if (COMPLEX_MODE_P (mode)) return 2; ... }