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From: "amker at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/66768] address space gets lost on literal pointer
Date: Tue, 07 Jul 2015 11:17:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66768

--- Comment #8 from amker at gcc dot gnu.org ---
So address space info is kept and checked in base object's type of MEM_REF.  As
in function expand_expr_real_1:

    case TARGET_MEM_REF:
      {
        addr_space_t as
          = TYPE_ADDR_SPACE (TREE_TYPE (TREE_TYPE (TREE_OPERAND (exp, 0))));
        enum insn_code icode;
        unsigned int align;

The AVR ICE happens when base of MEM_REF[base:0, index:(sizetype)ivtmp] has
__memx address space attribute.  Since pointer to memory object in __memx
address space (PSImode) has 24 bits type length, while the type of index is
sizetype(Pmode == HImode in this case), which has 16 bits type length.  The
expression "(sizetype)ivtmp" is expanded into (subreg:HI (reg:PSI 40) 0).

So I still think IVO should distribute ivtmp as base part of MEM_REF since it
stands for a memory object.  Otherwise, we have below IVOed code:

  <bb 3>:
  # total_10 = PHI <total_5(4), 0(2)>
  # ivtmp.7_8 = PHI <ivtmp.7_7(4), 4660(2)>
  _12 = (sizetype) ivtmp.7_8;
  _4 = MEM[base: 0B, index: _12, offset: 0B];
  total_5 = _4 + total_10;
  ivtmp.7_7 = ivtmp.7_8 + 2;
  if (ivtmp.7_7 != 4700)
    goto <bb 4>;
  else
    goto <bb 5>;

  <bb 4>:
  goto <bb 3>;


This is wrong since truncation of ivtmp.7_8 to sizetype could result in wrong
address.

Thanks.