The following fixes the PRs by not storing expressions inside
the reference ops for ARRAY_REFs for their element size but their
original operand 3.  This requires keeping track of the element
alignment and avoids any issues with not folding * /[ex] chains.
It also enables "real" VN of those ARRAY_REFs where previously
things like valueization wouldn't have worked on expression ops.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2016-07-18  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/71901
        * tree-ssa-sccvn.h (struct vn_reference_op_struct): Add
        align member, group stuff with the bitfield.
        (vn_ref_op_align_unit): New inline.
        * tree-ssa-sccvn.c (copy_reference_ops_from_ref): For ARRAY_REFs
        record element alignment and operand 3 unchanged.
        (ao_ref_init_from_vn_reference): Adjust.
        (valueize_refs_1): Likewise.
        * tree-ssa-pre.c (create_component_ref_by_pieces_1): Likewise.

        * gcc.dg/torture/pr71901.c: New testcase.

Index: gcc/tree-ssa-sccvn.h
===================================================================
*** gcc/tree-ssa-sccvn.h        (revision 238426)
--- gcc/tree-ssa-sccvn.h        (working copy)
*************** typedef const struct vn_phi_s *const_vn_
*** 81,102 ****
  typedef struct vn_reference_op_struct
  {
    ENUM_BITFIELD(tree_code) opcode : 16;
-   /* 1 for instrumented calls.  */
-   unsigned with_bounds : 1;
    /* Dependence info, used for [TARGET_]MEM_REF only.  */
    unsigned short clique;
    unsigned short base;
    /* Constant offset this op adds or -1 if it is variable.  */
    HOST_WIDE_INT off;
    tree type;
    tree op0;
    tree op1;
    tree op2;
-   bool reverse;
  } vn_reference_op_s;
  typedef vn_reference_op_s *vn_reference_op_t;
  typedef const vn_reference_op_s *const_vn_reference_op_t;
  
  
  /* A reference operation in the hashtable is representation as
     the vuse, representing the memory state at the time of
--- 81,109 ----
  typedef struct vn_reference_op_struct
  {
    ENUM_BITFIELD(tree_code) opcode : 16;
    /* Dependence info, used for [TARGET_]MEM_REF only.  */
    unsigned short clique;
    unsigned short base;
+   /* 1 for instrumented calls.  */
+   unsigned with_bounds : 1;
+   unsigned reverse : 1;
+   /* For storing TYPE_ALIGN for array ref element size computation.  */
+   unsigned align : 6;
    /* Constant offset this op adds or -1 if it is variable.  */
    HOST_WIDE_INT off;
    tree type;
    tree op0;
    tree op1;
    tree op2;
  } vn_reference_op_s;
  typedef vn_reference_op_s *vn_reference_op_t;
  typedef const vn_reference_op_s *const_vn_reference_op_t;
  
+ inline unsigned
+ vn_ref_op_align_unit (vn_reference_op_t op)
+ {
+   return op->align ? ((unsigned)1 << (op->align - 1)) / BITS_PER_UNIT : 0;
+ }
  
  /* A reference operation in the hashtable is representation as
     the vuse, representing the memory state at the time of
Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c  (revision 238426)
--- gcc/tree-ssa-pre.c  (working copy)
*************** create_component_ref_by_pieces_1 (basic_
*** 2570,2584 ****
               here as the element alignment may be not visible.  See
               PR43783.  Simply drop the element size for constant
               sizes.  */
!           if (tree_int_cst_equal (genop3, TYPE_SIZE_UNIT (elmt_type)))
              genop3 = NULL_TREE;
            else
              {
-               genop3 = size_binop (EXACT_DIV_EXPR, genop3,
-                                    size_int (TYPE_ALIGN_UNIT (elmt_type)));
-               /* We may have a useless conversion added by
-                  array_ref_element_size via copy_reference_opts_from_ref.  */
-               STRIP_USELESS_TYPE_CONVERSION (genop3);
                genop3 = find_or_generate_expression (block, genop3, stmts);
                if (!genop3)
                  return NULL_TREE;
--- 2581,2593 ----
               here as the element alignment may be not visible.  See
               PR43783.  Simply drop the element size for constant
               sizes.  */
!           if (TREE_CODE (genop3) == INTEGER_CST
!               && wi::eq_p (wi::to_offset (TYPE_SIZE_UNIT (elmt_type)),
!                            (wi::to_offset (genop3)
!                             * vn_ref_op_align_unit (currop))))
              genop3 = NULL_TREE;
            else
              {
                genop3 = find_or_generate_expression (block, genop3, stmts);
                if (!genop3)
                  return NULL_TREE;
Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c        (revision 238426)
--- gcc/tree-ssa-sccvn.c        (working copy)
*************** copy_reference_ops_from_ref (tree ref, v
*** 805,828 ****
          break;
        case ARRAY_RANGE_REF:
        case ARRAY_REF:
!         /* Record index as operand.  */
!         temp.op0 = TREE_OPERAND (ref, 1);
!         /* Always record lower bounds and element size.  */
!         temp.op1 = array_ref_low_bound (ref);
!         temp.op2 = array_ref_element_size (ref);
!         /* array_ref_element_size forces the result to sizetype
!            even if that is the same as bitsizetype.  */
!         STRIP_USELESS_TYPE_CONVERSION (temp.op2);
!         if (TREE_CODE (temp.op0) == INTEGER_CST
!             && TREE_CODE (temp.op1) == INTEGER_CST
!             && TREE_CODE (temp.op2) == INTEGER_CST)
!           {
!             offset_int off = ((wi::to_offset (temp.op0)
!                                - wi::to_offset (temp.op1))
!                               * wi::to_offset (temp.op2));
!             if (wi::fits_shwi_p (off))
!               temp.off = off.to_shwi();
!           }
          break;
        case VAR_DECL:
          if (DECL_HARD_REGISTER (ref))
--- 805,834 ----
          break;
        case ARRAY_RANGE_REF:
        case ARRAY_REF:
!         {
!           tree eltype = TREE_TYPE (TREE_TYPE (TREE_OPERAND (ref, 0)));
!           /* Record index as operand.  */
!           temp.op0 = TREE_OPERAND (ref, 1);
!           /* Always record lower bounds and element size.  */
!           temp.op1 = array_ref_low_bound (ref);
!           /* But record element size in units of the type alignment.  */
!           temp.op2 = TREE_OPERAND (ref, 3);
!           temp.align = eltype->type_common.align;
!           if (! temp.op2)
!             temp.op2 = size_binop (EXACT_DIV_EXPR, TYPE_SIZE_UNIT (eltype),
!                                    size_int (TYPE_ALIGN_UNIT (eltype)));
!           if (TREE_CODE (temp.op0) == INTEGER_CST
!               && TREE_CODE (temp.op1) == INTEGER_CST
!               && TREE_CODE (temp.op2) == INTEGER_CST)
!             {
!               offset_int off = ((wi::to_offset (temp.op0)
!                                  - wi::to_offset (temp.op1))
!                                 * wi::to_offset (temp.op2)
!                                 * vn_ref_op_align_unit (&temp));
!               if (wi::fits_shwi_p (off))
!                 temp.off = off.to_shwi();
!             }
!         }
          break;
        case VAR_DECL:
          if (DECL_HARD_REGISTER (ref))
*************** ao_ref_init_from_vn_reference (ao_ref *r
*** 1021,1027 ****
              offset_int woffset
                = wi::sext (wi::to_offset (op->op0) - wi::to_offset (op->op1),
                            TYPE_PRECISION (TREE_TYPE (op->op0)));
!             woffset *= wi::to_offset (op->op2);
              woffset <<= LOG2_BITS_PER_UNIT;
              offset += woffset;
            }
--- 1027,1033 ----
              offset_int woffset
                = wi::sext (wi::to_offset (op->op0) - wi::to_offset (op->op1),
                            TYPE_PRECISION (TREE_TYPE (op->op0)));
!             woffset *= wi::to_offset (op->op2) * vn_ref_op_align_unit (op);
              woffset <<= LOG2_BITS_PER_UNIT;
              offset += woffset;
            }
*************** valueize_refs_1 (vec<vn_reference_op_s>
*** 1471,1477 ****
        {
          offset_int off = ((wi::to_offset (vro->op0)
                             - wi::to_offset (vro->op1))
!                           * wi::to_offset (vro->op2));
          if (wi::fits_shwi_p (off))
            vro->off = off.to_shwi ();
        }
--- 1477,1484 ----
        {
          offset_int off = ((wi::to_offset (vro->op0)
                             - wi::to_offset (vro->op1))
!                           * wi::to_offset (vro->op2)
!                           * vn_ref_op_align_unit (vro));
          if (wi::fits_shwi_p (off))
            vro->off = off.to_shwi ();
        }
Index: gcc/testsuite/gcc.dg/torture/pr71901.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr71901.c      (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr71901.c      (working copy)
***************
*** 0 ****
--- 1,14 ----
+ /* { dg-do compile } */
+ 
+ typedef struct { int _mp_size; } mpz_t[1];
+ int a, b;
+ void fn1()
+ {
+   mpz_t c[1][b];
+   for (;;) {
+       int d = 0 >= 0 ? 0 == 0 ? c[0][0]->_mp_size ? -1 : 0 : 0 : 0,
+         e = 0 >= 0 ? 0 == 0 ? c[1][1]->_mp_size ? -1 : 0 : 0 : 0;
+       if (d != e)
+       a++;
+   }
+ }

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