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References: <bug-44790-3107@http.gcc.gnu.org/bugzilla/>
Subject: [Bug middle-end/44790] Bootstrap fails after MEM-REF merge
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From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
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------- Comment #2 from rguenth at gcc dot gnu dot org  2010-07-03 11:17 -------
The code in question is likely expr.c:8830 ff:

        address_mode = targetm.addr_space.address_mode (as);
        op0 = expand_expr (TREE_OPERAND (exp, 0), NULL_RTX, address_mode,
                           EXPAND_NORMAL);
        if (!integer_zerop (TREE_OPERAND (exp, 1)))
          {
            rtx off;
            off = immed_double_int_const (mem_ref_offset (exp), address_mode);
            op0 = simplify_gen_binary (PLUS, address_mode, op0, off);
          }
        op0 = memory_address_addr_space (mode, op0, as);
        temp = gen_rtx_MEM (mode, op0);

I see that POINTER_PLUS_EXPR would end up doing

;; ap_2 = ap_1 + 8;

(insn 10 9 11 t.i:8 (set (reg:SI 345)
        (plus:SI (subreg/s/v:SI (reg/v/f:DI 339 [ ap+-4 ]) 4)
            (const_int 8 [0x8]))) -1 (nil))

(insn 11 10 0 t.i:8 (set (reg/v/f:DI 340 [ ap+-4 ])
        (unspec:DI [
                (reg:SI 345)
            ] 24)) -1 (nil))

thus appearantly the pointer mode is DI but offsets are 32bit(?!)

OTOH doing

Index: expr.c
===================================================================
--- expr.c      (revision 161771)
+++ expr.c      (working copy)
@@ -8817,14 +8817,12 @@ expand_expr_real_1 (tree exp, rtx target
              }
          }
        address_mode = targetm.addr_space.address_mode (as);
-       op0 = expand_expr (TREE_OPERAND (exp, 0), NULL_RTX, address_mode,
-                          EXPAND_NORMAL);
+       base = TREE_OPERAND (exp, 0);
        if (!integer_zerop (TREE_OPERAND (exp, 1)))
-         {
-           rtx off;
-           off = immed_double_int_const (mem_ref_offset (exp), address_mode);
-           op0 = simplify_gen_binary (PLUS, address_mode, op0, off);
-         }
+         base = build2 (POINTER_PLUS_EXPR, TREE_TYPE (base),
+                        base, double_int_to_tree (sizetype,
+                                                  mem_ref_offset (exp)));
+       op0 = expand_expr (base, NULL_RTX, address_mode, EXPAND_SUM);
        op0 = memory_address_addr_space (mode, op0, as);
        temp = gen_rtx_MEM (mode, op0);
        set_mem_attributes (temp, exp, 0);

generates

(insn 13 12 14 t.i:8 (set (reg:DI 346)
        (reg/v/f:DI 339 [ ap+-4 ])) -1 (nil))

(insn 14 13 15 t.i:8 (set (reg/f:DI 347)
        (plus:DI (reg/v/f:DI 339 [ ap+-4 ])
            (const_int 4 [0x4]))) -1 (nil))

(insn 15 14 16 t.i:9 (set (reg:SI 348)
        (mem:SI (reg/f:DI 347) [0 MEM[(long int *)ap_1 + 4B]+0 S4 A32])) -1
(nil))

which doesn't use an UNSPEC either.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44790