[Bug jit/66812] jit code-generation example that unexpectedly required -fno-strict-aliasing to work

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66812

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Output from fre1 dump (at e.g. optlevel 3) (with TDF_DETAILS enabled) is:

;; Function test_pr66812 (test_pr66812, funcdef_no=0, decl_uid=56,
cgraph_uid=0, symbol_order=0)

Setting value number of .MEM_4(D) to .MEM_4(D) (changed)
Value numbering .MEM_5 stmt = MEM[(struct value *)arr_2(D) +
16B].union_field.i_field = 0;
RHS 0 simplified to 0
No store match
Value numbering store MEM[(struct value *)arr_2(D) + 16B].union_field.i_field
to 0
Setting value number of .MEM_5 to .MEM_5 (changed)
Value numbering .MEM_8 stmt = MEM[(struct value *)arr_2(D) + 16B].type_code =
0;
RHS 0 simplified to 0
No store match
Value numbering store MEM[(struct value *)arr_2(D) + 16B].type_code to 0
Setting value number of .MEM_8 to .MEM_8 (changed)
Value numbering .MEM_11 stmt = MEM[(struct value *)arr_2(D) +
16B].union_field.ll_field = 10;
RHS 10 simplified to 10
No store match
Value numbering store MEM[(struct value *)arr_2(D) + 16B].union_field.ll_field
to 10
Setting value number of .MEM_11 to .MEM_11 (changed)
Value numbering .MEM_14 stmt = MEM[(struct value *)arr_2(D) + 16B].type_code =
19;
RHS 19 simplified to 19
No store match
Value numbering store MEM[(struct value *)arr_2(D) + 16B].type_code to 19
Setting value number of .MEM_14 to .MEM_14 (changed)
Value numbering .MEM_17 stmt = MEM[(struct value *)arr_2(D) +
16B].union_field.i_field = 0;
RHS 0 simplified to 0
No store match
Value numbering store MEM[(struct value *)arr_2(D) + 16B].union_field.i_field
to 0
Setting value number of .MEM_17 to .MEM_17 (changed)
Value numbering .MEM_20 stmt = MEM[(struct value *)arr_2(D) + 16B].type_code =
0;
RHS 0 simplified to 0
No store match
Value numbering store MEM[(struct value *)arr_2(D) + 16B].type_code to 0
Setting value number of .MEM_20 to .MEM_20 (changed)
Value numbers:
Deleted redundant store MEM[(struct value *)arr_2(D) + 16B].union_field.i_field
= 0;
Removing dead stmt MEM[(struct value *)arr_2(D) + 16B].union_field.i_field = 0;
test_pr66812 (struct value * arr)
{
<L0>:
  MEM[(struct value *)arr_2(D) + 16B].union_field.i_field = 0;
  MEM[(struct value *)arr_2(D) + 16B].type_code = 0;
  MEM[(struct value *)arr_2(D) + 16B].union_field.ll_field = 10;
  MEM[(struct value *)arr_2(D) + 16B].type_code = 19;
  MEM[(struct value *)arr_2(D) + 16B].type_code = 0;
  return;

}