Re: [PATCH GCC]Pick up more address lowering cases for ivopt and tree-affine.c

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Nov 25, 2013 at 7:41 PM, Jeff Law <law@redhat.com> wrote:
> On 11/25/13 02:22, bin.cheng wrote:
>>
>> Hi,
>> I previously committed two patches lowering complex address expression for
>> IVOPT at http://gcc.gnu.org/ml/gcc-patches/2013-11/msg00546.html and
>> http://gcc.gnu.org/ml/gcc-patches/2013-11/msg01103.html
>> When I bootstrapping GCC I found there were some peculiar cases like
>> &MEM[ptr+CST] + xxxx, which should be handled too.  This patch consists
>> below two changes:
>>
>> 1) change in alloc_iv:
>> Original code lowers top level complex address expressions like
>> &MEM[ptr+off].  The patch relaxes check condition in order to lower
>> expressions like &MEM[ptr+off] + xxx, just as the BASE from below dump:
>> use 2
>>    generic
>>    in statement _595 = &MEM[(void *)&this_prg + 36B] + _594;
>>
>>    at position
>>    type struct gcov_bucket_type *
>>    base (struct gcov_bucket_type *) &MEM[(void *)&this_prg + 36B] +
>> (sizetype) ((unsigned int) (src_i_683 + -1) * 20)
>>    step 4294967276
>>    base object (void *) &this_prg
>>    related candidates
>>
>> 2) change in tree_to_aff_combination:
>> The function get_inner_reference returns "&MEM[ptr+off]" as the core for
>> input like the memory ADDRESS in below dump:
>> use 2
>>    address
>>    in statement _59 = MEM[(const struct gcov_ctr_summary *)summary_22(D) +
>> 4B].histogram[h_ix_111].min_value;
>>
>>    at position MEM[(const struct gcov_ctr_summary *)summary_22(D) +
>> 4B].histogram[h_ix_111].min_value
>>    type const gcov_type *
>>    base (const gcov_type *) &MEM[(const struct gcov_ctr_summary
>> *)summary_22(D) + 4B] + 36
>>    step 20
>>    base object (void *) summary_22(D)
>>    related candidates
>>
>> Which can be further reduced into something like "summary_22(D) + 40B".
>> This change is necessary for the first one, because I am using
>> tree_to_aff_combination rather than get_inner_reference_aff now.
>>
>> Bootstrap and test on x86/x86_64/arm.  Is it OK?
>>
>> Thanks.
>> bin
>>
>> 2013-11-25  Bin Cheng  <bin.cheng@arm.com>
>>
>>         * tree-ssa-loop-ivopts.c (contain_complex_addr_expr): New.
>>         (alloc_iv): Lower more cases by calling contain_complex_addr_expr
>>         and tree_to_aff_combination.
>>         * tree-affine.c (tree_to_aff_combination): Handle &MEM[ptr+CST]
>>         in core part of complex reference.
>>
>> gcc/testsuite/ChangeLog
>> 2013-11-25  Bin Cheng  <bin.cheng@arm.com>
>>
>>         * gcc.dg/tree-ssa/ivopts-lower_base.c: New test.
>
> Unless there's a PR for this problem, I think this needs to wait.

I agree.  Btw, please split the patch.

Index: gcc/tree-affine.c
===================================================================
--- gcc/tree-affine.c    (revision 205087)
+++ gcc/tree-affine.c    (working copy)
@@ -328,7 +328,19 @@ tree_to_aff_combination (tree expr, tree type, aff
                  double_int::from_uhwi (bitpos / BITS_PER_UNIT));
       core = build_fold_addr_expr (core);
       if (TREE_CODE (core) == ADDR_EXPR)
-    aff_combination_add_elt (comb, core, double_int_one);
+    {
+      /* Handle &MEM[ptr + CST] in core part of complex reference.  */
+      if (TREE_CODE (TREE_OPERAND (core, 0)) == MEM_REF)
+        {
+          core = TREE_OPERAND (core, 0);
+          tree_to_aff_combination (TREE_OPERAND (core, 0), type, &tmp);
+          aff_combination_add (comb, &tmp);
+          tree_to_aff_combination (TREE_OPERAND (core, 1), sizetype, &tmp);
+          aff_combination_add (comb, &tmp);
+        }
+      else
+        aff_combination_add_elt (comb, core, double_int_one);
+    }
       else
     {
       tree_to_aff_combination (core, type, &tmp)

please handle the offset before taking the address, thus

  if (TREE_CODE (core) == MEM_REF)
    {
       add constant offset;
       core = TREE_OPERAND (core, 0);
    }
  else
    core = build_fold_addr_expr (core);

that simplifies things and avoids the address building.

Richard.

> jeff
>
>