[PATCH] Fix PR71816

[Richard Biener]

The following patch fixes PR71816.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.

Richard.

2016-07-11  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/71816
        * tree-ssa-pre.c (compute_avail): Adjust alignment of ref rather
        than replacing all of its operands.

        * gcc.dg/torture/pr71816.c: New testcase.

Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c  (revision 238206)
--- gcc/tree-ssa-pre.c  (working copy)
*************** compute_avail (void)
*** 3791,3803 ****
                           || ref1->opcode == MEM_REF)
                          && (TYPE_ALIGN (ref1->type)
                              > TYPE_ALIGN (ref2->type)))
!                       {
!                         ref->operands.release ();
!                         ref->operands = operands;
!                         ref1 = ref2;
!                       }
!                     else
!                       operands.release ();
                      /* TBAA behavior is an obvious part so make sure
                         that the hashtable one covers this as well
                         by adjusting the ref alias set and its base.  */
--- 3791,3799 ----
                           || ref1->opcode == MEM_REF)
                          && (TYPE_ALIGN (ref1->type)
                              > TYPE_ALIGN (ref2->type)))
!                       ref1->type
!                         = build_aligned_type (ref1->type,
!                                               TYPE_ALIGN (ref2->type));
                      /* TBAA behavior is an obvious part so make sure
                         that the hashtable one covers this as well
                         by adjusting the ref alias set and its base.  */
*************** compute_avail (void)
*** 3824,3829 ****
--- 3820,3826 ----
                            ref1->op2 = fold_convert (ptr_type_node,
                                                      ref1->op2);
                        }
+                     operands.release ();
  
                      result = pre_expr_pool.allocate ();
                      result->kind = REFERENCE;
Index: gcc/testsuite/gcc.dg/torture/pr71816.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr71816.c      (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr71816.c      (working copy)
***************
*** 0 ****
--- 1,21 ----
+ /* { dg-do compile } */
+ 
+ void *ext2fs_resize_mem_p;
+ struct ext2_icount_el {
+     int ino;
+ } * insert_icount_el_icount_1;
+ int insert_icount_el_icount, insert_icount_el_new_size;
+ void *memcpy();
+ void *realloc();
+ int ext2fs_resize_mem(void *p1) {
+     int size = 0;
+     memcpy(&ext2fs_resize_mem_p, p1, sizeof(ext2fs_resize_mem_p));
+     realloc(&ext2fs_resize_mem_p, size);
+     return 0;
+ }
+ struct ext2_icount_el *insert_icount_el() {
+     if (insert_icount_el_icount)
+       insert_icount_el_new_size = insert_icount_el_icount_1[0].ino;
+     ext2fs_resize_mem(&insert_icount_el_icount_1);
+     return 0;
+ }