https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112773
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Last reconfirmed| |2023-12-01 --- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> --- The issue might be we do not use vec_extract for memory arguments: /* Use vec_extract patterns for extracting parts of vectors whenever available. If that fails, see whether the current modes and bitregion give a natural subreg. */ machine_mode outermode = GET_MODE (op0); if (VECTOR_MODE_P (outermode) && !MEM_P (op0)) { and somehow the original reg operand got spilled inbetween. That happens here, after we could make vec_extract work for this. /* Make sure we are playing with integral modes. Pun with subregs if we aren't. */ opt_scalar_int_mode op0_mode = int_mode_for_mode (GET_MODE (op0)); scalar_int_mode imode; if (!op0_mode.exists (&imode) || imode != GET_MODE (op0)) { ... else { poly_int64 size = GET_MODE_SIZE (GET_MODE (op0)); rtx mem = assign_stack_temp (GET_MODE (op0), size); emit_move_insn (mem, op0); op0 = adjust_bitfield_address_size (mem, BLKmode, 0, size); } now, if we spilled we can elide the round-down I think (which is for the fear of accessing invalid memory). Thus like the following? diff --git a/gcc/expmed.cc b/gcc/expmed.cc index b294eabb08d..e2b38b87bdf 100644 --- a/gcc/expmed.cc +++ b/gcc/expmed.cc @@ -1856,7 +1856,7 @@ extract_bit_field_1 (rtx str_rtx, poly_uint64 bitsize, poly_uint64 bitnum, /* If we have a memory source and a non-constant bit offset, restrict the memory to the referenced bytes. This is a worst-case fallback but is useful for things like vector booleans. */ - if (MEM_P (op0) && !bitnum.is_constant ()) + if (MEM_P (str_rtx) && !bitnum.is_constant ()) { bytenum = bits_to_bytes_round_down (bitnum); bitnum = num_trailing_bits (bitnum); but that defers the ICE to during RTL pass: expand t.c: In function 'e': t.c:4:6: internal compiler error: in to_constant, at poly-int.h:588 4 | void e(unsigned f) { | ^ 0x10ea530 poly_int<2u, unsigned long>::to_constant() const /home/rguenther/src/trunk/gcc/poly-int.h:588 0x13cec67 extract_bit_field_1 /home/rguenther/src/trunk/gcc/expmed.cc:1872 so I guess we really need to match the vec_extract pattern. So you need to debug why that doesn't match here.