[Bug middle-end/112830] internal compiler error: in convert_memory_address_addr_space_1, at explow.cc:302

["gjl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112830

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |avr
           Keywords|                            |addr-space,
                   |                            |ice-on-valid-code

--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
In explow.cc, we have:

rtx convert_memory_address_addr_space_1 (...)
{
#ifndef POINTERS_EXTEND_UNSIGNED
  gcc_assert (GET_MODE (x) == to_mode || GET_MODE (x) == VOIDmode); // line 302
  return x;
#else /* defined(POINTERS_EXTEND_UNSIGNED) */

so it seems the backend has to define POINTERS_EXTEND_UNSIGNED, which it
currently doesn't.  However, the documentation of PEU reads:

> Macro: POINTERS_EXTEND_UNSIGNED
>   A C expression that determines how pointers should be extended from
>   ptr_mode to either Pmode or word_mode. It is greater than zero if
>   pointers should be zero-extended, zero if they should be sign-extended,
>   and negative if some other sort of conversion is needed. In the last case,
>   the extension is done by the target’s ptr_extend instruction.
>   You need not define this macro if the ptr_mode, Pmode and word_mode are
>   all the same width. 

The avr backend has:

Pmode = word_mode = HImode (16 bits), mode for ADDR_SPACE_GENERIC

PSImode = 24 bits, mode for ADDR_SPACE_MEMX, aka. __memx

So it appear the middle-end wants to "extend" a pointer from 24-bit PSImode to
16-bit Pmode, which makes no sense.  Apart from that, the code does not require
any pointer adjustments.

One guess is that the middle-end tries to expand the memcpy, because insn
cpymemhi only support CONST_INT lengths, and gets somethig wrong about address
spaces.

The backend defines TARGET_ADDR_SPACE_CONVERT, and
TARGET_ADDR_SPACE_ADDRESS_MODE is the same like TARGET_ADDR_SPACE_POINTER_MODE
for all address spaces.