[PATCH] Ensure DEBUG_INSNs don't contain MEMs with non-canonical MEM_EXPRs (PR debug/48134)

[Richard Guenther]

On Thu, Mar 17, 2011 at 9:41 AM, Richard Guenther
<richard.guenther@gmail.com> wrote:
> On Thu, Mar 17, 2011 at 12:32 AM, Jakub Jelinek <jakub@redhat.com> wrote:
>> Hi!
>>
>> Currently expand_debug_expr doesn't always guarantee canonical
>> MEM_EXPRs, if MEM_EXPR isn't canonical, sometimes aliasing code ICEs on it
>> (since recent Richard's change fortunately only if --enable-checking=yes).
>>
>> The following patch canonicalizes those using fold and if canonicalization
>> isn't successful, just clears the MEM_EXPR.
>>
>> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
>> 4.6.1?
>>
>> 2011-03-17  Jakub Jelinek  <jakub@redhat.com>
>>
>>        PR debug/48134
>>        * cfgexpand.c (expand_debug_expr) <component_ref>: Use fold to
>>        canonicalize MEM_EXPR, if it still isn't canonical afterwards, just
>>        clear MEM_EXPR.
>>
>>        * gcc.dg/pr48134.c: New test.
>>
>> --- gcc/cfgexpand.c.jj  2011-03-16 18:30:12.000000000 +0100
>> +++ gcc/cfgexpand.c     2011-03-16 22:05:13.000000000 +0100
>> @@ -2712,6 +2712,8 @@ expand_debug_expr (tree exp)
>>
>>        if (MEM_P (op0))
>>          {
>> +           tree mem_exp;
>> +
>>            if (mode1 == VOIDmode)
>>              /* Bitfield.  */
>>              mode1 = smallest_mode_for_size (bitsize, MODE_INT);
>> @@ -2736,6 +2738,12 @@ expand_debug_expr (tree exp)
>>            if (op0 == orig_op0)
>>              op0 = shallow_copy_rtx (op0);
>>            set_mem_attributes (op0, exp, 0);
>> +           mem_exp = fold (exp);
>> +           if (!SSA_VAR_P (mem_exp)
>> +               && TREE_CODE (mem_exp) != MEM_REF
>> +               && TREE_CODE (mem_exp) != TARGET_MEM_REF)
>> +             mem_exp = NULL_TREE;
>> +           set_mem_expr (op0, mem_exp);
>
> That will, for the testcase drop the MEM[&t.s].w completely, right?
> I think you eventually want to use maybe_fold_reference which does
> canonicalize mem-refs after propagation (but also watch for bogus
> debug information due to constant folding of initializers I
> ran into because of setting DECL_INITIAL to error_mark_node for
> unused globals - I'll try to dig up the patch I had to fix that).

I am testing the following.

Richard.
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