This fixes the dependency of vectorization of strided loads on
gather support.  For that to work we need to lift the restriction
in data-ref analysis that requries a constant DR_STEP.  Fortunately
fallout is small.

As a side-effect the data-reference for strided loads now makes
sense (rather than being gobbled over by gather analysis BB-level DR).

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

Richard.

2012-05-11  Richard Guenther  <rguent...@suse.de>

        * tree-data-ref.h (stride_of_unit_type_p): Handle non-constant
        strides.
        * tree-data-ref.c (dr_analyze_innermost): Allow non-constant
        strides when analyzing data-references in a loop context.
        * tree-vect-data-refs.c (vect_mark_for_runtime_alias_test): Reject
        non-constant strides for now.
        (vect_enhance_data_refs_alignment): Ignore data references
        that are strided loads.
        (vect_analyze_data_ref_access): Handle non-constant strides.
        (vect_check_strided_load): Verify the data-reference is a load.
        (vect_analyze_data_refs): Restructure to make strided load
        support not dependent on gather support.
        * tree-vect-stmts.c (vectorizable_load): Avoid useless work
        when doing strided or gather loads.
        * tree-vect-loop-manip.c (vect_vfa_segment_size): Use
        integer_zerop to compare stride with zero.

Index: gcc/tree-data-ref.h
===================================================================
*** gcc/tree-data-ref.h (revision 187396)
--- gcc/tree-data-ref.h (working copy)
*************** bool stmt_with_adjacent_zero_store_dr_p
*** 618,626 ****
  static inline bool
  stride_of_unit_type_p (tree stride, tree type)
  {
!   return tree_int_cst_equal (fold_unary (ABS_EXPR, TREE_TYPE (stride),
!                                        stride),
!                            TYPE_SIZE_UNIT (type));
  }
  
  /* Determines whether RDG vertices V1 and V2 access to similar memory
--- 618,627 ----
  static inline bool
  stride_of_unit_type_p (tree stride, tree type)
  {
!   return (TREE_CODE (stride) == INTEGER_CST
!         && tree_int_cst_equal (fold_unary (ABS_EXPR, TREE_TYPE (stride),
!                                            stride),
!                                TYPE_SIZE_UNIT (type)));
  }
  
  /* Determines whether RDG vertices V1 and V2 access to similar memory
Index: gcc/tree-data-ref.c
===================================================================
*** gcc/tree-data-ref.c (revision 187396)
--- gcc/tree-data-ref.c (working copy)
*************** dr_analyze_innermost (struct data_refere
*** 736,742 ****
    if (in_loop)
      {
        if (!simple_iv (loop, loop_containing_stmt (stmt), base, &base_iv,
!                       false))
          {
            if (nest)
              {
--- 736,742 ----
    if (in_loop)
      {
        if (!simple_iv (loop, loop_containing_stmt (stmt), base, &base_iv,
!                       nest ? true : false))
          {
            if (nest)
              {
*************** dr_analyze_innermost (struct data_refere
*** 773,779 ****
            offset_iv.step = ssize_int (0);
          }
        else if (!simple_iv (loop, loop_containing_stmt (stmt),
!                            poffset, &offset_iv, false))
          {
            if (nest)
              {
--- 773,780 ----
            offset_iv.step = ssize_int (0);
          }
        else if (!simple_iv (loop, loop_containing_stmt (stmt),
!                            poffset, &offset_iv,
!                          nest ? true : false))
          {
            if (nest)
              {
Index: gcc/tree-vect-data-refs.c
===================================================================
*** gcc/tree-vect-data-refs.c   (revision 187396)
--- gcc/tree-vect-data-refs.c   (working copy)
*************** vect_mark_for_runtime_alias_test (ddr_p
*** 542,547 ****
--- 542,558 ----
        return false;
      }
  
+   /* FORNOW: We don't support creating runtime alias tests for non-constant
+      step.  */
+   if (TREE_CODE (DR_STEP (DDR_A (ddr))) != INTEGER_CST
+       || TREE_CODE (DR_STEP (DDR_B (ddr))) != INTEGER_CST)
+     {
+       if (vect_print_dump_info (REPORT_DR_DETAILS))
+       fprintf (vect_dump, "versioning not yet supported for non-constant "
+                "step");
+       return false;
+     }
+ 
    VEC_safe_push (ddr_p, heap, LOOP_VINFO_MAY_ALIAS_DDRS (loop_vinfo), ddr);
    return true;
  }
*************** vect_enhance_data_refs_alignment (loop_v
*** 1522,1527 ****
--- 1533,1543 ----
        if (integer_zerop (DR_STEP (dr)))
        continue;
  
+       /* Strided loads perform only component accesses, alignment is
+        irrelevant for them.  */
+       if (STMT_VINFO_STRIDE_LOAD_P (stmt_info))
+       continue;
+ 
        supportable_dr_alignment = vect_supportable_dr_alignment (dr, true);
        do_peeling = vector_alignment_reachable_p (dr);
        if (do_peeling)
*************** vect_enhance_data_refs_alignment (loop_v
*** 1779,1784 ****
--- 1795,1805 ----
              && GROUP_FIRST_ELEMENT (stmt_info) != stmt)
            continue;
  
+         /* Strided loads perform only component accesses, alignment is
+            irrelevant for them.  */
+         if (STMT_VINFO_STRIDE_LOAD_P (stmt_info))
+           continue;
+ 
          save_misalignment = DR_MISALIGNMENT (dr);
          vect_update_misalignment_for_peel (dr, dr0, npeel);
          supportable_dr_alignment = vect_supportable_dr_alignment (dr, false);
*************** vect_enhance_data_refs_alignment (loop_v
*** 1861,1866 ****
--- 1882,1892 ----
                  && GROUP_FIRST_ELEMENT (stmt_info) != stmt))
            continue;
  
+         /* Strided loads perform only component accesses, alignment is
+            irrelevant for them.  */
+         if (STMT_VINFO_STRIDE_LOAD_P (stmt_info))
+           continue;
+ 
          supportable_dr_alignment = vect_supportable_dr_alignment (dr, false);
  
            if (!supportable_dr_alignment)
*************** vect_analyze_data_ref_access (struct dat
*** 2329,2335 ****
    stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
    loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
    struct loop *loop = NULL;
-   HOST_WIDE_INT dr_step;
  
    if (loop_vinfo)
      loop = LOOP_VINFO_LOOP (loop_vinfo);
--- 2355,2360 ----
*************** vect_analyze_data_ref_access (struct dat
*** 2342,2349 ****
      }
  
    /* Allow invariant loads in loops.  */
!   dr_step = TREE_INT_CST_LOW (step);
!   if (loop_vinfo && dr_step == 0)
      {
        GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;
        return DR_IS_READ (dr);
--- 2367,2373 ----
      }
  
    /* Allow invariant loads in loops.  */
!   if (loop_vinfo && integer_zerop (step))
      {
        GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;
        return DR_IS_READ (dr);
*************** vect_analyze_data_ref_access (struct dat
*** 2357,2365 ****
  
        /* For the rest of the analysis we use the outer-loop step.  */
        step = STMT_VINFO_DR_STEP (stmt_info);
!       dr_step = TREE_INT_CST_LOW (step);
! 
!       if (dr_step == 0)
        {
          if (vect_print_dump_info (REPORT_ALIGNMENT))
            fprintf (vect_dump, "zero step in outer loop.");
--- 2381,2387 ----
  
        /* For the rest of the analysis we use the outer-loop step.  */
        step = STMT_VINFO_DR_STEP (stmt_info);
!       if (integer_zerop (step))
        {
          if (vect_print_dump_info (REPORT_ALIGNMENT))
            fprintf (vect_dump, "zero step in outer loop.");
*************** vect_analyze_data_ref_access (struct dat
*** 2371,2383 ****
      }
  
    /* Consecutive?  */
!   if (!tree_int_cst_compare (step, TYPE_SIZE_UNIT (scalar_type))
!       || (dr_step < 0
!         && !compare_tree_int (TYPE_SIZE_UNIT (scalar_type), -dr_step)))
      {
!       /* Mark that it is not interleaving.  */
!       GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;
!       return true;
      }
  
    if (loop && nested_in_vect_loop_p (loop, stmt))
--- 2393,2409 ----
      }
  
    /* Consecutive?  */
!   if (TREE_CODE (step) == INTEGER_CST)
      {
!       HOST_WIDE_INT dr_step = TREE_INT_CST_LOW (step);
!       if (!tree_int_cst_compare (step, TYPE_SIZE_UNIT (scalar_type))
!         || (dr_step < 0
!             && !compare_tree_int (TYPE_SIZE_UNIT (scalar_type), -dr_step)))
!       {
!         /* Mark that it is not interleaving.  */
!         GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;
!         return true;
!       }
      }
  
    if (loop && nested_in_vect_loop_p (loop, stmt))
*************** vect_analyze_data_ref_access (struct dat
*** 2387,2392 ****
--- 2413,2422 ----
        return false;
      }
  
+   /* Assume this is a DR handled by non-constant strided load case.  */
+   if (TREE_CODE (step) != INTEGER_CST)
+     return STMT_VINFO_STRIDE_LOAD_P (stmt_info);
+ 
    /* Not consecutive access - check if it's a part of interleaving group.  */
    return vect_analyze_group_access (dr);
  }
*************** vect_check_strided_load (gimple stmt, lo
*** 2720,2725 ****
--- 2750,2758 ----
    tree base, off;
    affine_iv iv;
  
+   if (!DR_IS_READ (dr))
+     return false;
+ 
    base = DR_REF (dr);
  
    if (TREE_CODE (base) == ARRAY_REF)
*************** vect_analyze_data_refs (loop_vec_info lo
*** 3148,3168 ****
          VEC (ddr_p, heap) *ddrs = LOOP_VINFO_DDRS (loop_vinfo);
          struct data_dependence_relation *ddr, *newddr;
          bool bad = false;
-         bool strided_load = false;
          tree off;
          VEC (loop_p, heap) *nest = LOOP_VINFO_LOOP_NEST (loop_vinfo);
  
-         strided_load = vect_check_strided_load (stmt, loop_vinfo, NULL, NULL);
          gather = 0 != vect_check_gather (stmt, loop_vinfo, NULL, &off, NULL);
          if (gather
              && get_vectype_for_scalar_type (TREE_TYPE (off)) == NULL_TREE)
            gather = false;
!         if (!gather && !strided_load)
            {
              if (vect_print_dump_info (REPORT_UNVECTORIZED_LOCATIONS))
                {
                  fprintf (vect_dump,
!                          "not vectorized: not suitable for gather/strided 
load ");
                  print_gimple_stmt (vect_dump, stmt, 0, TDF_SLIM);
                }
              return false;
--- 3181,3199 ----
          VEC (ddr_p, heap) *ddrs = LOOP_VINFO_DDRS (loop_vinfo);
          struct data_dependence_relation *ddr, *newddr;
          bool bad = false;
          tree off;
          VEC (loop_p, heap) *nest = LOOP_VINFO_LOOP_NEST (loop_vinfo);
  
          gather = 0 != vect_check_gather (stmt, loop_vinfo, NULL, &off, NULL);
          if (gather
              && get_vectype_for_scalar_type (TREE_TYPE (off)) == NULL_TREE)
            gather = false;
!         if (!gather)
            {
              if (vect_print_dump_info (REPORT_UNVECTORIZED_LOCATIONS))
                {
                  fprintf (vect_dump,
!                          "not vectorized: not suitable for gather load ");
                  print_gimple_stmt (vect_dump, stmt, 0, TDF_SLIM);
                }
              return false;
*************** vect_analyze_data_refs (loop_vec_info lo
*** 3215,3230 ****
                {
                  fprintf (vect_dump,
                           "not vectorized: data dependence conflict"
!                          " prevents gather/strided load");
                  print_gimple_stmt (vect_dump, stmt, 0, TDF_SLIM);
                }
              return false;
            }
  
!         if (gather)
!           STMT_VINFO_GATHER_P (stmt_info) = true;
!         else if (strided_load)
!           STMT_VINFO_STRIDE_LOAD_P (stmt_info) = true;
        }
      }
  
--- 3246,3277 ----
                {
                  fprintf (vect_dump,
                           "not vectorized: data dependence conflict"
!                          " prevents gather load");
                  print_gimple_stmt (vect_dump, stmt, 0, TDF_SLIM);
                }
              return false;
            }
  
!         STMT_VINFO_GATHER_P (stmt_info) = true;
!       }
!       else if (loop_vinfo
!              && TREE_CODE (DR_STEP (dr)) != INTEGER_CST)
!       {
!         bool strided_load = false;
!         if (!nested_in_vect_loop_p (loop, stmt))
!           strided_load
!             = vect_check_strided_load (stmt, loop_vinfo, NULL, NULL);
!         if (!strided_load)
!           {
!             if (vect_print_dump_info (REPORT_UNVECTORIZED_LOCATIONS))
!               {
!                 fprintf (vect_dump,
!                          "not vectorized: not suitable for strided load ");
!                 print_gimple_stmt (vect_dump, stmt, 0, TDF_SLIM);
!               }
!             return false;
!           }
!         STMT_VINFO_STRIDE_LOAD_P (stmt_info) = true;
        }
      }
  
Index: gcc/tree-vect-stmts.c
===================================================================
*** gcc/tree-vect-stmts.c       (revision 187396)
--- gcc/tree-vect-stmts.c       (working copy)
*************** vectorizable_load (gimple stmt, gimple_s
*** 4210,4216 ****
    bool load_lanes_p = false;
    gimple first_stmt;
    bool inv_p;
!   bool negative;
    bool compute_in_loop = false;
    struct loop *at_loop;
    int vec_num;
--- 4210,4216 ----
    bool load_lanes_p = false;
    gimple first_stmt;
    bool inv_p;
!   bool negative = false;
    bool compute_in_loop = false;
    struct loop *at_loop;
    int vec_num;
*************** vectorizable_load (gimple stmt, gimple_s
*** 4280,4296 ****
    if (!STMT_VINFO_DATA_REF (stmt_info))
      return false;
  
-   negative = tree_int_cst_compare (nested_in_vect_loop
-                                  ? STMT_VINFO_DR_STEP (stmt_info)
-                                  : DR_STEP (dr),
-                                  size_zero_node) < 0;
-   if (negative && ncopies > 1)
-     {
-       if (vect_print_dump_info (REPORT_DETAILS))
-         fprintf (vect_dump, "multiple types with negative step.");
-       return false;
-     }
- 
    elem_type = TREE_TYPE (vectype);
    mode = TYPE_MODE (vectype);
  
--- 4280,4285 ----
*************** vectorizable_load (gimple stmt, gimple_s
*** 4321,4344 ****
        }
      }
  
-   if (negative)
-     {
-       gcc_assert (!grouped_load && !STMT_VINFO_GATHER_P (stmt_info));
-       alignment_support_scheme = vect_supportable_dr_alignment (dr, false);
-       if (alignment_support_scheme != dr_aligned
-         && alignment_support_scheme != dr_unaligned_supported)
-       {
-         if (vect_print_dump_info (REPORT_DETAILS))
-           fprintf (vect_dump, "negative step but alignment required.");
-         return false;
-       }
-       if (!perm_mask_for_reverse (vectype))
-       {
-         if (vect_print_dump_info (REPORT_DETAILS))
-           fprintf (vect_dump, "negative step and reversing not supported.");
-         return false;
-       }
-     }
  
    if (STMT_VINFO_GATHER_P (stmt_info))
      {
--- 4310,4315 ----
*************** vectorizable_load (gimple stmt, gimple_s
*** 4358,4364 ****
      }
    else if (STMT_VINFO_STRIDE_LOAD_P (stmt_info))
      {
!       vect_check_strided_load (stmt, loop_vinfo, &stride_base, &stride_step);
      }
  
    if (!vec_stmt) /* transformation not required.  */
--- 4329,4369 ----
      }
    else if (STMT_VINFO_STRIDE_LOAD_P (stmt_info))
      {
!       if (!vect_check_strided_load (stmt, loop_vinfo,
!                                   &stride_base, &stride_step))
!       return false;
!     }
!   else
!     {
!       negative = tree_int_cst_compare (nested_in_vect_loop
!                                      ? STMT_VINFO_DR_STEP (stmt_info)
!                                      : DR_STEP (dr),
!                                      size_zero_node) < 0;
!       if (negative && ncopies > 1)
!       {
!         if (vect_print_dump_info (REPORT_DETAILS))
!           fprintf (vect_dump, "multiple types with negative step.");
!         return false;
!       }
! 
!       if (negative)
!       {
!         gcc_assert (!grouped_load);
!         alignment_support_scheme = vect_supportable_dr_alignment (dr, false);
!         if (alignment_support_scheme != dr_aligned
!             && alignment_support_scheme != dr_unaligned_supported)
!           {
!             if (vect_print_dump_info (REPORT_DETAILS))
!               fprintf (vect_dump, "negative step but alignment required.");
!             return false;
!           }
!         if (!perm_mask_for_reverse (vectype))
!           {
!             if (vect_print_dump_info (REPORT_DETAILS))
!               fprintf (vect_dump, "negative step and reversing not 
supported.");
!             return false;
!           }
!       }
      }
  
    if (!vec_stmt) /* transformation not required.  */
Index: gcc/tree-vect-loop-manip.c
===================================================================
*** gcc/tree-vect-loop-manip.c  (revision 187396)
--- gcc/tree-vect-loop-manip.c  (working copy)
*************** vect_vfa_segment_size (struct data_refer
*** 2334,2340 ****
  {
    tree segment_length;
  
!   if (!compare_tree_int (DR_STEP (dr), 0))
      segment_length = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr)));
    else
      segment_length = size_binop (MULT_EXPR,
--- 2334,2340 ----
  {
    tree segment_length;
  
!   if (integer_zerop (DR_STEP (dr)))
      segment_length = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr)));
    else
      segment_length = size_binop (MULT_EXPR,

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