SRA: Total scalarization after access propagation [PR92706]
authorMartin Jambor <mjambor@suse.cz>
Wed, 29 Jan 2020 12:13:13 +0000 (13:13 +0100)
committerMartin Jambor <mjambor@suse.cz>
Wed, 29 Jan 2020 12:13:13 +0000 (13:13 +0100)
2020-01-29  Martin Jambor  <mjambor@suse.cz>

PR tree-optimization/92706
* tree-sra.c (struct access): Adjust comment of
grp_total_scalarization.
(find_access_in_subtree): Look for single children spanning an entire
access.
(scalarizable_type_p): Allow register accesses, adjust callers.
(completely_scalarize): Remove function.
(scalarize_elem): Likewise.
(create_total_scalarization_access): Likewise.
(sort_and_splice_var_accesses): Do not track total scalarization
flags.
(analyze_access_subtree): New parameter totally, adjust to new meaning
of grp_total_scalarization.
(analyze_access_trees): Pass new parameter to analyze_access_subtree.
(can_totally_scalarize_forest_p): New function.
(create_total_scalarization_access): Likewise.
(create_total_access_and_reshape): Likewise.
(total_should_skip_creating_access): Likewise.
(totally_scalarize_subtree): Likewise.
(analyze_all_variable_accesses): Perform total scalarization after
subaccess propagation using the new functions above.
(initialize_constant_pool_replacements): Output initializers by
traversing the access tree.

testsuite/
* gcc.dg/tree-ssa/pr92706-2.c: New test.
* gcc.dg/guality/pr59776.c: Xfail tests for s2.g.

gcc/ChangeLog
gcc/testsuite/ChangeLog
gcc/testsuite/gcc.dg/guality/pr59776.c
gcc/testsuite/gcc.dg/tree-ssa/pr92706-2.c [new file with mode: 0644]
gcc/tree-sra.c

index 16247a59304acd39c46f40bf4c460f168b4eafb3..61da54df34638e9aeea7960e3f5e5d92c703f423 100644 (file)
@@ -1,3 +1,29 @@
+2020-01-29  Martin Jambor  <mjambor@suse.cz>
+
+       PR tree-optimization/92706
+       * tree-sra.c (struct access): Adjust comment of
+       grp_total_scalarization.
+       (find_access_in_subtree): Look for single children spanning an entire
+       access.
+       (scalarizable_type_p): Allow register accesses, adjust callers.
+       (completely_scalarize): Remove function.
+       (scalarize_elem): Likewise.
+       (create_total_scalarization_access): Likewise.
+       (sort_and_splice_var_accesses): Do not track total scalarization
+       flags.
+       (analyze_access_subtree): New parameter totally, adjust to new meaning
+       of grp_total_scalarization.
+       (analyze_access_trees): Pass new parameter to analyze_access_subtree.
+       (can_totally_scalarize_forest_p): New function.
+       (create_total_scalarization_access): Likewise.
+       (create_total_access_and_reshape): Likewise.
+       (total_should_skip_creating_access): Likewise.
+       (totally_scalarize_subtree): Likewise.
+       (analyze_all_variable_accesses): Perform total scalarization after
+       subaccess propagation using the new functions above.
+       (initialize_constant_pool_replacements): Output initializers by
+       traversing the access tree.
+
 2020-01-29  Martin Jambor  <mjambor@suse.cz>
 
        * tree-sra.c (verify_sra_access_forest): New function.
index 055188488293a26709a05317c07954eba2008ac3..38758207989c09359bfe6ccc6bcd74f42dd949df 100644 (file)
@@ -1,3 +1,9 @@
+2020-01-29  Martin Jambor  <mjambor@suse.cz>
+
+       PR tree-optimization/92706
+       * gcc.dg/tree-ssa/pr92706-2.c: New test.
+       * gcc.dg/guality/pr59776.c: Xfail tests for s2.g.
+
 2020-01-28  Jan Hubicka  <hubicka@ucw.cz>
 
        * gcc.dg/tree-prof/indir-call-prof-2.c: New testcase.
index 382abb622bbd4e01bfdfb7a29a20f8d5348d5e7d..6c1c8165b70748bbf181202a695730fb2bf485b6 100644 (file)
@@ -12,11 +12,11 @@ foo (struct S *p)
   struct S s1, s2;                     /* { dg-final { gdb-test pr59776.c:17 "s1.f" "5.0" } } */
   s1 = *p;                             /* { dg-final { gdb-test pr59776.c:17 "s1.g" "6.0" } } */
   s2 = s1;                             /* { dg-final { gdb-test pr59776.c:17 "s2.f" "0.0" } } */
-  *(int *) &s2.f = 0;                  /* { dg-final { gdb-test pr59776.c:17 "s2.g" "6.0" } } */
+  *(int *) &s2.f = 0;                  /* { dg-final { gdb-test pr59776.c:17 "s2.g" "6.0" { xfail *-*-* } } } */
   asm volatile (NOP : : : "memory");   /* { dg-final { gdb-test pr59776.c:20 "s1.f" "5.0" } } */
   asm volatile (NOP : : : "memory");   /* { dg-final { gdb-test pr59776.c:20 "s1.g" "6.0" } } */
   s2 = s1;                             /* { dg-final { gdb-test pr59776.c:20 "s2.f" "5.0" } } */
-  asm volatile (NOP : : : "memory");   /* { dg-final { gdb-test pr59776.c:20 "s2.g" "6.0" } } */
+  asm volatile (NOP : : : "memory");   /* { dg-final { gdb-test pr59776.c:20 "s2.g" "6.0" { xfail *-*-* } } } */
   asm volatile (NOP : : : "memory");
 }
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr92706-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr92706-2.c
new file mode 100644 (file)
index 0000000..37ab976
--- /dev/null
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-esra" } */
+
+typedef __UINT64_TYPE__ uint64_t;
+typedef __UINT32_TYPE__ uint32_t;
+struct S { uint32_t i[2]; } __attribute__((aligned(__alignof__(uint64_t))));
+typedef uint64_t my_int64 __attribute__((may_alias));
+uint64_t load (void *p)
+{
+  struct S u, v, w;
+  uint64_t tem;
+  tem = *(my_int64 *)p;
+  *(my_int64 *)&v = tem;
+  u = v;
+  w = u;
+  return *(my_int64 *)&w;
+}
+
+/* { dg-final { scan-tree-dump "Created a replacement for v" "esra" } } */
index 36106fecaf181c7b9e2abfce6b6b9decaabbafb3..2b0849858de5a62e4915d4e89d651e1ca598b368 100644 (file)
@@ -211,8 +211,11 @@ struct access
      is not propagated in the access tree in any direction.  */
   unsigned grp_scalar_write : 1;
 
-  /* Is this access an artificial one created to scalarize some record
-     entirely? */
+  /* In a root of an access tree, true means that the entire tree should be
+     totally scalarized - that all scalar leafs should be scalarized and
+     non-root grp_total_scalarization accesses should be honored.  Otherwise,
+     non-root accesses with grp_total_scalarization should never get scalar
+     replacements.  */
   unsigned grp_total_scalarization : 1;
 
   /* Other passes of the analysis use this bit to make function
@@ -485,6 +488,15 @@ find_access_in_subtree (struct access *access, HOST_WIDE_INT offset,
       access = child;
     }
 
+  /* Total scalarization does not replace single field structures with their
+     single field but rather creates an access for them underneath.  Look for
+     it.  */
+  if (access)
+    while (access->first_child
+          && access->first_child->offset == offset
+          && access->first_child->size == size)
+      access = access->first_child;
+
   return access;
 }
 
@@ -856,7 +868,8 @@ create_access (tree expr, gimple *stmt, bool write)
 static bool
 scalarizable_type_p (tree type, bool const_decl)
 {
-  gcc_assert (!is_gimple_reg_type (type));
+  if (is_gimple_reg_type (type))
+    return true;
   if (type_contains_placeholder_p (type))
     return false;
 
@@ -871,8 +884,7 @@ scalarizable_type_p (tree type, bool const_decl)
          if (DECL_BIT_FIELD (fld))
            return false;
 
-         if (!is_gimple_reg_type (ft)
-             && !scalarizable_type_p (ft, const_decl))
+         if (!scalarizable_type_p (ft, const_decl))
            return false;
        }
 
@@ -902,8 +914,7 @@ scalarizable_type_p (tree type, bool const_decl)
        return false;
 
       tree elem = TREE_TYPE (type);
-      if (!is_gimple_reg_type (elem)
-         && !scalarizable_type_p (elem, const_decl))
+      if (!scalarizable_type_p (elem, const_decl))
        return false;
       return true;
     }
@@ -912,114 +923,6 @@ scalarizable_type_p (tree type, bool const_decl)
   }
 }
 
-static void scalarize_elem (tree, HOST_WIDE_INT, HOST_WIDE_INT, bool, tree, tree);
-
-/* Create total_scalarization accesses for all scalar fields of a member
-   of type DECL_TYPE conforming to scalarizable_type_p.  BASE
-   must be the top-most VAR_DECL representing the variable; within that,
-   OFFSET locates the member and REF must be the memory reference expression for
-   the member.  */
-
-static void
-completely_scalarize (tree base, tree decl_type, HOST_WIDE_INT offset, tree ref)
-{
-  switch (TREE_CODE (decl_type))
-    {
-    case RECORD_TYPE:
-      for (tree fld = TYPE_FIELDS (decl_type); fld; fld = DECL_CHAIN (fld))
-       if (TREE_CODE (fld) == FIELD_DECL)
-         {
-           HOST_WIDE_INT pos = offset + int_bit_position (fld);
-           tree ft = TREE_TYPE (fld);
-           tree nref = build3 (COMPONENT_REF, ft, ref, fld, NULL_TREE);
-
-           scalarize_elem (base, pos, tree_to_uhwi (DECL_SIZE (fld)),
-                           TYPE_REVERSE_STORAGE_ORDER (decl_type),
-                           nref, ft);
-         }
-      break;
-    case ARRAY_TYPE:
-      {
-       tree elemtype = TREE_TYPE (decl_type);
-       tree elem_size = TYPE_SIZE (elemtype);
-       gcc_assert (elem_size && tree_fits_shwi_p (elem_size));
-       HOST_WIDE_INT el_size = tree_to_shwi (elem_size);
-       gcc_assert (el_size > 0);
-
-       tree minidx = TYPE_MIN_VALUE (TYPE_DOMAIN (decl_type));
-       gcc_assert (TREE_CODE (minidx) == INTEGER_CST);
-       tree maxidx = TYPE_MAX_VALUE (TYPE_DOMAIN (decl_type));
-       /* Skip (some) zero-length arrays; others have MAXIDX == MINIDX - 1.  */
-       if (maxidx)
-         {
-           gcc_assert (TREE_CODE (maxidx) == INTEGER_CST);
-           tree domain = TYPE_DOMAIN (decl_type);
-           /* MINIDX and MAXIDX are inclusive, and must be interpreted in
-              DOMAIN (e.g. signed int, whereas min/max may be size_int).  */
-           offset_int idx = wi::to_offset (minidx);
-           offset_int max = wi::to_offset (maxidx);
-           if (!TYPE_UNSIGNED (domain))
-             {
-               idx = wi::sext (idx, TYPE_PRECISION (domain));
-               max = wi::sext (max, TYPE_PRECISION (domain));
-             }
-           for (int el_off = offset; idx <= max; ++idx)
-             {
-               tree nref = build4 (ARRAY_REF, elemtype,
-                                   ref,
-                                   wide_int_to_tree (domain, idx),
-                                   NULL_TREE, NULL_TREE);
-               scalarize_elem (base, el_off, el_size,
-                               TYPE_REVERSE_STORAGE_ORDER (decl_type),
-                               nref, elemtype);
-               el_off += el_size;
-             }
-         }
-      }
-      break;
-    default:
-      gcc_unreachable ();
-    }
-}
-
-/* Create total_scalarization accesses for a member of type TYPE, which must
-   satisfy either is_gimple_reg_type or scalarizable_type_p.  BASE must be the
-   top-most VAR_DECL representing the variable; within that, POS and SIZE locate
-   the member, REVERSE gives its torage order. and REF must be the reference
-   expression for it.  */
-
-static void
-scalarize_elem (tree base, HOST_WIDE_INT pos, HOST_WIDE_INT size, bool reverse,
-               tree ref, tree type)
-{
-  if (is_gimple_reg_type (type))
-  {
-    struct access *access = create_access_1 (base, pos, size);
-    access->expr = ref;
-    access->type = type;
-    access->grp_total_scalarization = 1;
-    access->reverse = reverse;
-    /* Accesses for intraprocedural SRA can have their stmt NULL.  */
-  }
-  else
-    completely_scalarize (base, type, pos, ref);
-}
-
-/* Create a total_scalarization access for VAR as a whole.  VAR must be of a
-   RECORD_TYPE or ARRAY_TYPE conforming to scalarizable_type_p.  */
-
-static void
-create_total_scalarization_access (tree var)
-{
-  HOST_WIDE_INT size = tree_to_uhwi (DECL_SIZE (var));
-  struct access *access;
-
-  access = create_access_1 (var, 0, size);
-  access->expr = var;
-  access->type = TREE_TYPE (var);
-  access->grp_total_scalarization = 1;
-}
-
 /* Return true if REF has an VIEW_CONVERT_EXPR somewhere in it.  */
 
 static inline bool
@@ -2029,7 +1932,6 @@ sort_and_splice_var_accesses (tree var)
       bool grp_assignment_read = access->grp_assignment_read;
       bool grp_assignment_write = access->grp_assignment_write;
       bool multiple_scalar_reads = false;
-      bool total_scalarization = access->grp_total_scalarization;
       bool grp_partial_lhs = access->grp_partial_lhs;
       bool first_scalar = is_gimple_reg_type (access->type);
       bool unscalarizable_region = access->grp_unscalarizable_region;
@@ -2081,7 +1983,6 @@ sort_and_splice_var_accesses (tree var)
          grp_assignment_write |= ac2->grp_assignment_write;
          grp_partial_lhs |= ac2->grp_partial_lhs;
          unscalarizable_region |= ac2->grp_unscalarizable_region;
-         total_scalarization |= ac2->grp_total_scalarization;
          relink_to_new_repr (access, ac2);
 
          /* If there are both aggregate-type and scalar-type accesses with
@@ -2122,9 +2023,7 @@ sort_and_splice_var_accesses (tree var)
       access->grp_scalar_write = grp_scalar_write;
       access->grp_assignment_read = grp_assignment_read;
       access->grp_assignment_write = grp_assignment_write;
-      access->grp_hint = total_scalarization
-       || (multiple_scalar_reads && !constant_decl_p (var));
-      access->grp_total_scalarization = total_scalarization;
+      access->grp_hint = multiple_scalar_reads && !constant_decl_p (var);
       access->grp_partial_lhs = grp_partial_lhs;
       access->grp_unscalarizable_region = unscalarizable_region;
       access->grp_same_access_path = grp_same_access_path;
@@ -2420,15 +2319,16 @@ expr_with_var_bounded_array_refs_p (tree expr)
 }
 
 /* Analyze the subtree of accesses rooted in ROOT, scheduling replacements when
-   both seeming beneficial and when ALLOW_REPLACEMENTS allows it.  Also set all
-   sorts of access flags appropriately along the way, notably always set
-   grp_read and grp_assign_read according to MARK_READ and grp_write when
-   MARK_WRITE is true.
+   both seeming beneficial and when ALLOW_REPLACEMENTS allows it.  If TOTALLY
+   is set, we are totally scalarizing the aggregate.  Also set all sorts of
+   access flags appropriately along the way, notably always set grp_read and
+   grp_assign_read according to MARK_READ and grp_write when MARK_WRITE is
+   true.
 
    Creating a replacement for a scalar access is considered beneficial if its
-   grp_hint is set (this means we are either attempting total scalarization or
-   there is more than one direct read access) or according to the following
-   table:
+   grp_hint ot TOTALLY is set (this means either that there is more than one
+   direct read access or that we are attempting total scalarization) or
+   according to the following table:
 
    Access written to through a scalar type (once or more times)
    |
@@ -2459,7 +2359,7 @@ expr_with_var_bounded_array_refs_p (tree expr)
 
 static bool
 analyze_access_subtree (struct access *root, struct access *parent,
-                       bool allow_replacements)
+                       bool allow_replacements, bool totally)
 {
   struct access *child;
   HOST_WIDE_INT limit = root->offset + root->size;
@@ -2477,8 +2377,6 @@ analyze_access_subtree (struct access *root, struct access *parent,
        root->grp_write = 1;
       if (parent->grp_assignment_write)
        root->grp_assignment_write = 1;
-      if (parent->grp_total_scalarization)
-       root->grp_total_scalarization = 1;
       if (!parent->grp_same_access_path)
        root->grp_same_access_path = 0;
     }
@@ -2493,10 +2391,10 @@ analyze_access_subtree (struct access *root, struct access *parent,
     {
       hole |= covered_to < child->offset;
       sth_created |= analyze_access_subtree (child, root,
-                                            allow_replacements && !scalar);
+                                            allow_replacements && !scalar,
+                                            totally);
 
       root->grp_unscalarized_data |= child->grp_unscalarized_data;
-      root->grp_total_scalarization &= child->grp_total_scalarization;
       if (child->grp_covered)
        covered_to += child->size;
       else
@@ -2504,7 +2402,9 @@ analyze_access_subtree (struct access *root, struct access *parent,
     }
 
   if (allow_replacements && scalar && !root->first_child
-      && (root->grp_hint
+      && (totally || !root->grp_total_scalarization)
+      && (totally
+         || root->grp_hint
          || ((root->grp_scalar_read || root->grp_assignment_read)
              && (root->grp_scalar_write || root->grp_assignment_write))))
     {
@@ -2546,6 +2446,7 @@ analyze_access_subtree (struct access *root, struct access *parent,
     {
       if (allow_replacements
          && scalar && !root->first_child
+         && !root->grp_total_scalarization
          && (root->grp_scalar_write || root->grp_assignment_write)
          && !bitmap_bit_p (cannot_scalarize_away_bitmap,
                            DECL_UID (root->base)))
@@ -2566,7 +2467,7 @@ analyze_access_subtree (struct access *root, struct access *parent,
        root->grp_total_scalarization = 0;
     }
 
-  if (!hole || root->grp_total_scalarization)
+  if (!hole || totally)
     root->grp_covered = 1;
   else if (root->grp_write || comes_initialized_p (root->base))
     root->grp_unscalarized_data = 1; /* not covered and written to */
@@ -2582,7 +2483,8 @@ analyze_access_trees (struct access *access)
 
   while (access)
     {
-      if (analyze_access_subtree (access, NULL, true))
+      if (analyze_access_subtree (access, NULL, true,
+                                 access->grp_total_scalarization))
        ret = true;
       access = access->next_grp;
     }
@@ -2855,6 +2757,369 @@ propagate_all_subaccesses (void)
     }
 }
 
+/* Return true if the forest beginning with ROOT does not contain
+   unscalarizable regions or non-byte aligned accesses.  */
+
+static bool
+can_totally_scalarize_forest_p (struct access *root)
+{
+  struct access *access = root;
+  do
+    {
+      if (access->grp_unscalarizable_region
+         || (access->offset % BITS_PER_UNIT) != 0
+         || (access->size % BITS_PER_UNIT) != 0
+         || (is_gimple_reg_type (access->type)
+             && access->first_child))
+       return false;
+
+      if (access->first_child)
+       access = access->first_child;
+      else if (access->next_sibling)
+       access = access->next_sibling;
+      else
+       {
+         while (access->parent && !access->next_sibling)
+           access = access->parent;
+         if (access->next_sibling)
+           access = access->next_sibling;
+         else
+           {
+             gcc_assert (access == root);
+             root = root->next_grp;
+             access = root;
+           }
+       }
+    }
+  while (access);
+  return true;
+}
+
+/* Create and return an ACCESS in PARENT spanning from POS with SIZE, TYPE and
+   reference EXPR for total scalarization purposes and mark it as such.  Within
+   the children of PARENT, link it in between PTR and NEXT_SIBLING.  */
+
+static struct access *
+create_total_scalarization_access (struct access *parent, HOST_WIDE_INT pos,
+                                  HOST_WIDE_INT size, tree type, tree expr,
+                                  struct access **ptr,
+                                  struct access *next_sibling)
+{
+  struct access *access = access_pool.allocate ();
+  memset (access, 0, sizeof (struct access));
+  access->base = parent->base;
+  access->offset = pos;
+  access->size = size;
+  access->expr = expr;
+  access->type = type;
+  access->parent = parent;
+  access->grp_write = parent->grp_write;
+  access->grp_total_scalarization = 1;
+  access->grp_hint = 1;
+  access->grp_same_access_path = path_comparable_for_same_access (expr);
+  access->reverse = reverse_storage_order_for_component_p (expr);
+
+  access->next_sibling = next_sibling;
+  *ptr = access;
+  return access;
+}
+
+/* Create and return an ACCESS in PARENT spanning from POS with SIZE, TYPE and
+   reference EXPR for total scalarization purposes and mark it as such, link it
+   at *PTR and reshape the tree so that those elements at *PTR and their
+   siblings which fall within the part described by POS and SIZE are moved to
+   be children of the new access.  If a partial overlap is detected, return
+   NULL.  */
+
+static struct access *
+create_total_access_and_reshape (struct access *parent, HOST_WIDE_INT pos,
+                                HOST_WIDE_INT size, tree type, tree expr,
+                                struct access **ptr)
+{
+  struct access **p = ptr;
+
+  while (*p && (*p)->offset < pos + size)
+    {
+      if ((*p)->offset + (*p)->size > pos + size)
+       return NULL;
+      p = &(*p)->next_sibling;
+    }
+
+  struct access *next_child = *ptr;
+  struct access *new_acc
+    = create_total_scalarization_access (parent, pos, size, type, expr,
+                                        ptr, *p);
+  if (p != ptr)
+    {
+      new_acc->first_child = next_child;
+      *p = NULL;
+      for (struct access *a = next_child; a; a = a->next_sibling)
+       a->parent = new_acc;
+    }
+  return new_acc;
+}
+
+static bool totally_scalarize_subtree (struct access *root);
+
+/* Return true if INNER is either the same type as OUTER or if it is the type
+   of a record field in OUTER at offset zero, possibly in nested
+   sub-records.  */
+
+static bool
+access_and_field_type_match_p (tree outer, tree inner)
+{
+  if (TYPE_MAIN_VARIANT (outer) == TYPE_MAIN_VARIANT (inner))
+    return true;
+  if (TREE_CODE (outer) != RECORD_TYPE)
+    return false;
+  tree fld = TYPE_FIELDS (outer);
+  while (fld)
+    {
+     if (TREE_CODE (fld) == FIELD_DECL)
+       {
+       if (!zerop (DECL_FIELD_OFFSET (fld)))
+         return false;
+       if (TYPE_MAIN_VARIANT (TREE_TYPE (fld)) == inner)
+         return true;
+       if (TREE_CODE (TREE_TYPE (fld)) == RECORD_TYPE)
+         fld = TYPE_FIELDS (TREE_TYPE (fld));
+       else
+         return false;
+       }
+     else
+       fld = DECL_CHAIN (fld);
+    }
+  return false;
+}
+
+/* Return type of total_should_skip_creating_access indicating whether a total
+   scalarization access for a field/element should be created, whether it
+   already exists or whether the entire total scalarization has to fail.  */
+
+enum total_sra_field_state {TOTAL_FLD_CREATE, TOTAL_FLD_DONE, TOTAL_FLD_FAILED};
+
+/* Do all the necessary steps in total scalarization when the given aggregate
+   type has a TYPE at POS with the given SIZE should be put into PARENT and
+   when we have processed all its siblings with smaller offsets up until and
+   including LAST_SEEN_SIBLING (which can be NULL).
+
+   If some further siblings are to be skipped, set *LAST_SEEN_SIBLING as
+   appropriate.  Return TOTAL_FLD_CREATE id the caller should carry on with
+   creating a new access, TOTAL_FLD_DONE if access or accesses capable of
+   representing the described part of the aggregate for the purposes of total
+   scalarization already exist or TOTAL_FLD_FAILED if there is a problem which
+   prevents total scalarization from happening at all.  */
+
+static enum total_sra_field_state
+total_should_skip_creating_access (struct access *parent,
+                                  struct access **last_seen_sibling,
+                                  tree type, HOST_WIDE_INT pos,
+                                  HOST_WIDE_INT size)
+{
+  struct access *next_child;
+  if (!*last_seen_sibling)
+    next_child = parent->first_child;
+  else
+    next_child = (*last_seen_sibling)->next_sibling;
+
+  /* First, traverse the chain of siblings until it points to an access with
+     offset at least equal to POS.  Check all skipped accesses whether they
+     span the POS boundary and if so, return with a failure.  */
+  while (next_child && next_child->offset < pos)
+    {
+      if (next_child->offset + next_child->size > pos)
+       return TOTAL_FLD_FAILED;
+      *last_seen_sibling = next_child;
+      next_child = next_child->next_sibling;
+    }
+
+  /* Now check whether next_child has exactly the right POS and SIZE and if so,
+     whether it can represent what we need and can be totally scalarized
+     itself.  */
+  if (next_child && next_child->offset == pos
+      && next_child->size == size)
+    {
+      if (!is_gimple_reg_type (next_child->type)
+         && (!access_and_field_type_match_p (type, next_child->type)
+             || !totally_scalarize_subtree (next_child)))
+       return TOTAL_FLD_FAILED;
+
+      *last_seen_sibling = next_child;
+      return TOTAL_FLD_DONE;
+    }
+
+  /* If the child we're looking at would partially overlap, we just cannot
+     totally scalarize.  */
+  if (next_child
+      && next_child->offset < pos + size
+      && next_child->offset + next_child->size > pos + size)
+    return TOTAL_FLD_FAILED;
+
+  if (is_gimple_reg_type (type))
+    {
+      /* We don't scalarize accesses that are children of other scalar type
+        accesses, so if we go on and create an access for a register type,
+        there should not be any pre-existing children.  There are rare cases
+        where the requested type is a vector but we already have register
+        accesses for all its elements which is equally good.  Detect that
+        situation or whether we need to bail out.  */
+
+      HOST_WIDE_INT covered = pos;
+      bool skipping = false;
+      while (next_child
+            && next_child->offset + next_child->size <= pos + size)
+       {
+         if (next_child->offset != covered
+             || !is_gimple_reg_type (next_child->type))
+           return TOTAL_FLD_FAILED;
+
+         covered += next_child->size;
+         *last_seen_sibling = next_child;
+         next_child = next_child->next_sibling;
+         skipping = true;
+       }
+
+      if (skipping)
+       {
+         if (covered != pos + size)
+           return TOTAL_FLD_FAILED;
+         else
+           return TOTAL_FLD_DONE;
+       }
+    }
+
+  return TOTAL_FLD_CREATE;
+}
+
+/* Go over sub-tree rooted in ROOT and attempt to create scalar accesses
+   spanning all uncovered areas covered by ROOT, return false if the attempt
+   failed.  All created accesses will have grp_unscalarizable_region set (and
+   should be ignored if the function returns false).  */
+
+static bool
+totally_scalarize_subtree (struct access *root)
+{
+  gcc_checking_assert (!root->grp_unscalarizable_region);
+  gcc_checking_assert (!is_gimple_reg_type (root->type));
+
+  struct access *last_seen_sibling = NULL;
+
+  switch (TREE_CODE (root->type))
+    {
+    case RECORD_TYPE:
+      for (tree fld = TYPE_FIELDS (root->type); fld; fld = DECL_CHAIN (fld))
+       if (TREE_CODE (fld) == FIELD_DECL)
+         {
+           tree ft = TREE_TYPE (fld);
+           HOST_WIDE_INT fsize = tree_to_uhwi (DECL_SIZE (fld));
+           if (!fsize)
+             continue;
+
+           HOST_WIDE_INT pos = root->offset + int_bit_position (fld);
+           enum total_sra_field_state
+             state = total_should_skip_creating_access (root,
+                                                        &last_seen_sibling,
+                                                        ft, pos, fsize);
+           switch (state)
+             {
+             case TOTAL_FLD_FAILED:
+               return false;
+             case TOTAL_FLD_DONE:
+               continue;
+             case TOTAL_FLD_CREATE:
+               break;
+             default:
+               gcc_unreachable ();
+             }
+
+           struct access **p = (last_seen_sibling
+                                ? &last_seen_sibling->next_sibling
+                                : &root->first_child);
+           tree nref = build3 (COMPONENT_REF, ft, root->expr, fld, NULL_TREE);
+           struct access *new_child
+             = create_total_access_and_reshape (root, pos, fsize, ft, nref, p);
+           if (!new_child)
+             return false;
+
+           if (!is_gimple_reg_type (ft)
+               && !totally_scalarize_subtree (new_child))
+             return false;
+           last_seen_sibling = new_child;
+         }
+      break;
+    case ARRAY_TYPE:
+      {
+       tree elemtype = TREE_TYPE (root->type);
+       tree elem_size = TYPE_SIZE (elemtype);
+       gcc_assert (elem_size && tree_fits_shwi_p (elem_size));
+       HOST_WIDE_INT el_size = tree_to_shwi (elem_size);
+       gcc_assert (el_size > 0);
+
+       tree minidx = TYPE_MIN_VALUE (TYPE_DOMAIN (root->type));
+       gcc_assert (TREE_CODE (minidx) == INTEGER_CST);
+       tree maxidx = TYPE_MAX_VALUE (TYPE_DOMAIN (root->type));
+       /* Skip (some) zero-length arrays; others have MAXIDX == MINIDX - 1.  */
+       if (!maxidx)
+         goto out;
+       gcc_assert (TREE_CODE (maxidx) == INTEGER_CST);
+       tree domain = TYPE_DOMAIN (root->type);
+       /* MINIDX and MAXIDX are inclusive, and must be interpreted in
+          DOMAIN (e.g. signed int, whereas min/max may be size_int).  */
+       offset_int idx = wi::to_offset (minidx);
+       offset_int max = wi::to_offset (maxidx);
+       if (!TYPE_UNSIGNED (domain))
+         {
+           idx = wi::sext (idx, TYPE_PRECISION (domain));
+           max = wi::sext (max, TYPE_PRECISION (domain));
+         }
+       for (HOST_WIDE_INT pos = root->offset;
+            idx <= max;
+            pos += el_size, ++idx)
+         {
+           enum total_sra_field_state
+             state = total_should_skip_creating_access (root,
+                                                        &last_seen_sibling,
+                                                        elemtype, pos,
+                                                        el_size);
+           switch (state)
+             {
+             case TOTAL_FLD_FAILED:
+               return false;
+             case TOTAL_FLD_DONE:
+               continue;
+             case TOTAL_FLD_CREATE:
+               break;
+             default:
+               gcc_unreachable ();
+             }
+
+           struct access **p = (last_seen_sibling
+                                ? &last_seen_sibling->next_sibling
+                                : &root->first_child);
+           tree nref = build4 (ARRAY_REF, elemtype, root->expr,
+                               wide_int_to_tree (domain, idx),
+                               NULL_TREE, NULL_TREE);
+           struct access *new_child
+             = create_total_access_and_reshape (root, pos, el_size, elemtype,
+                                                nref, p);
+           if (!new_child)
+             return false;
+
+           if (!is_gimple_reg_type (elemtype)
+               && !totally_scalarize_subtree (new_child))
+             return false;
+           last_seen_sibling = new_child;
+         }
+      }
+      break;
+    default:
+      gcc_unreachable ();
+    }
+
+ out:
+  return true;
+}
+
 /* Go through all accesses collected throughout the (intraprocedural) analysis
    stage, exclude overlapping ones, identify representatives and build trees
    out of them, making decisions about scalarization on the way.  Return true
@@ -2867,8 +3132,22 @@ analyze_all_variable_accesses (void)
   bitmap tmp = BITMAP_ALLOC (NULL);
   bitmap_iterator bi;
   unsigned i;
-  bool optimize_speed_p = !optimize_function_for_size_p (cfun);
 
+  bitmap_copy (tmp, candidate_bitmap);
+  EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi)
+    {
+      tree var = candidate (i);
+      struct access *access;
+
+      access = sort_and_splice_var_accesses (var);
+      if (!access || !build_access_trees (access))
+       disqualify_candidate (var,
+                             "No or inhibitingly overlapping accesses.");
+    }
+
+  propagate_all_subaccesses ();
+
+  bool optimize_speed_p = !optimize_function_for_size_p (cfun);
   /* If the user didn't set PARAM_SRA_MAX_SCALARIZATION_SIZE_<...>,
      fall back to a target default.  */
   unsigned HOST_WIDE_INT max_scalarization_size
@@ -2884,7 +3163,6 @@ analyze_all_variable_accesses (void)
       if (global_options_set.x_param_sra_max_scalarization_size_size)
        max_scalarization_size = param_sra_max_scalarization_size_size;
     }
-
   max_scalarization_size *= BITS_PER_UNIT;
 
   EXECUTE_IF_SET_IN_BITMAP (candidate_bitmap, 0, i, bi)
@@ -2892,46 +3170,56 @@ analyze_all_variable_accesses (void)
        && !bitmap_bit_p (cannot_scalarize_away_bitmap, i))
       {
        tree var = candidate (i);
+       if (!VAR_P (var))
+         continue;
 
-       if (VAR_P (var) && scalarizable_type_p (TREE_TYPE (var),
-                                               constant_decl_p (var)))
+       if (tree_to_uhwi (TYPE_SIZE (TREE_TYPE (var))) > max_scalarization_size)
          {
-           if (tree_to_uhwi (TYPE_SIZE (TREE_TYPE (var)))
-               <= max_scalarization_size)
-             {
-               create_total_scalarization_access (var);
-               completely_scalarize (var, TREE_TYPE (var), 0, var);
-               statistics_counter_event (cfun,
-                                         "Totally-scalarized aggregates", 1);
-               if (dump_file && (dump_flags & TDF_DETAILS))
-                 {
-                   fprintf (dump_file, "Will attempt to totally scalarize ");
-                   print_generic_expr (dump_file, var);
-                   fprintf (dump_file, " (UID: %u): \n", DECL_UID (var));
-                 }
-             }
-           else if (dump_file && (dump_flags & TDF_DETAILS))
+           if (dump_file && (dump_flags & TDF_DETAILS))
              {
                fprintf (dump_file, "Too big to totally scalarize: ");
                print_generic_expr (dump_file, var);
                fprintf (dump_file, " (UID: %u)\n", DECL_UID (var));
              }
+           continue;
          }
-      }
 
-  bitmap_copy (tmp, candidate_bitmap);
-  EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi)
-    {
-      tree var = candidate (i);
-      struct access *access;
+       bool all_types_ok = true;
+       for (struct access *access = get_first_repr_for_decl (var);
+            access;
+            access = access->next_grp)
+         if (!can_totally_scalarize_forest_p (access)
+             || !scalarizable_type_p (access->type, constant_decl_p (var)))
+           {
+             all_types_ok = false;
+             break;
+           }
+       if (!all_types_ok)
+         continue;
 
-      access = sort_and_splice_var_accesses (var);
-      if (!access || !build_access_trees (access))
-       disqualify_candidate (var,
-                             "No or inhibitingly overlapping accesses.");
-    }
+       if (dump_file && (dump_flags & TDF_DETAILS))
+         {
+           fprintf (dump_file, "Will attempt to totally scalarize ");
+           print_generic_expr (dump_file, var);
+           fprintf (dump_file, " (UID: %u): \n", DECL_UID (var));
+         }
+       bool scalarized = true;
+       for (struct access *access = get_first_repr_for_decl (var);
+            access;
+            access = access->next_grp)
+         if (!is_gimple_reg_type (access->type)
+             && !totally_scalarize_subtree (access))
+           {
+             scalarized = false;
+             break;
+           }
 
-  propagate_all_subaccesses ();
+       if (scalarized)
+         for (struct access *access = get_first_repr_for_decl (var);
+              access;
+              access = access->next_grp)
+           access->grp_total_scalarization = true;
+      }
 
   if (flag_checking)
     verify_all_sra_access_forests ();
@@ -3804,25 +4092,39 @@ initialize_constant_pool_replacements (void)
       tree var = candidate (i);
       if (!constant_decl_p (var))
        continue;
-      vec<access_p> *access_vec = get_base_access_vector (var);
-      if (!access_vec)
-       continue;
-      for (unsigned i = 0; i < access_vec->length (); i++)
+
+      struct access *access = get_first_repr_for_decl (var);
+
+      while (access)
        {
-         struct access *access = (*access_vec)[i];
-         if (!access->replacement_decl)
-           continue;
-         gassign *stmt
-           = gimple_build_assign (get_access_replacement (access),
-                                  unshare_expr (access->expr));
-         if (dump_file && (dump_flags & TDF_DETAILS))
+         if (access->replacement_decl)
            {
-             fprintf (dump_file, "Generating constant initializer: ");
-             print_gimple_stmt (dump_file, stmt, 0);
-             fprintf (dump_file, "\n");
+             gassign *stmt
+               = gimple_build_assign (get_access_replacement (access),
+                                      unshare_expr (access->expr));
+             if (dump_file && (dump_flags & TDF_DETAILS))
+               {
+                 fprintf (dump_file, "Generating constant initializer: ");
+                 print_gimple_stmt (dump_file, stmt, 0);
+                 fprintf (dump_file, "\n");
+               }
+             gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
+             update_stmt (stmt);
+           }
+
+         if (access->first_child)
+           access = access->first_child;
+         else if (access->next_sibling)
+           access = access->next_sibling;
+         else
+           {
+             while (access->parent && !access->next_sibling)
+               access = access->parent;
+             if (access->next_sibling)
+               access = access->next_sibling;
+             else
+               access = access->next_grp;
            }
-         gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
-         update_stmt (stmt);
        }
     }