[Bug target/111720] RISC-V: Ugly codegen in RVV

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111720

--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
With RVV you have intrinsic calls in GIMPLE so nothing to optimize:

vbool8_t fn ()
{
  vbool8_t vmask;
  vuint8m1_t vand_m;
  vuint8m1_t varr;
  uint8_t arr[32];

  <bb 2> [local count: 1073741824]:
  arr =
"\x01\x02\x07\x01\x03\x04\x05\x03\x01\x00\x01\x02\x04\x04\t\t\x01\x02\x07\x01\x03\x04\x05\x03\x01\x00\x01\x02\x04\x04\t\t";
  varr_3 = __riscv_vle8_v_u8m1 (&arr, 32); [return slot optimization]
  vand_m_4 = __riscv_vand_vx_u8m1 (varr_3, 1, 32); [return slot optimization]
  vmask_5 = __riscv_vreinterpret_v_u8m1_b8 (vand_m_4); [return slot
optimization]
  <retval> = vmask_5;
  arr ={v} {CLOBBER(eol)};
  return <retval>;

and on RTL I see lots of UNSPECs, RTL opts cannot do anything with those.

This is what Andrew said already.