[PATCH 1/4] SRA: Add verification of accesses

[Martin Jambor]

Hi,

this patch has not changed since the last submission at all, in fact
it got approved but without the follow-up fix of the reverse flag, it
would introduce regression, so it should not be committed on its own.

Because the follow-up patches perform some non-trivial operations on
SRA patches, I wrote myself a verifier.  And sure enough, it has
spotted two issues, one of which is fixed in this patch too - we did
not correctly set the parent link when creating artificial accesses
for propagation across assignments.  The second one is the (not)
setting of reverse flag when creating accesses for total scalarization
but since the following patch removes the offending function, this
patch does not fix it.

Bootstrapped and tested on x86_64, I consider this a pre-requisite for
the followup patches (and the parent link fix really is).

Thanks,

Martin

2019-12-10  Martin Jambor  <mjambor@suse.cz>

	* tree-sra.c (verify_sra_access_forest): New function.
	(verify_all_sra_access_forests): Likewise.
	(create_artificial_child_access): Set parent.
	(analyze_all_variable_accesses): Call the verifier.
---
 gcc/tree-sra.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 875d5b21763..36106fecaf1 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -2321,6 +2321,88 @@ build_access_trees (struct access *access)
   return true;
 }
 
+/* Traverse the access forest where ROOT is the first root and verify that
+   various important invariants hold true.  */
+
+DEBUG_FUNCTION void
+verify_sra_access_forest (struct access *root)
+{
+  struct access *access = root;
+  tree first_base = root->base;
+  gcc_assert (DECL_P (first_base));
+  do
+    {
+      gcc_assert (access->base == first_base);
+      if (access->parent)
+	gcc_assert (access->offset >= access->parent->offset
+		    && access->size <= access->parent->size);
+      if (access->next_sibling)
+	gcc_assert (access->next_sibling->offset
+		    >= access->offset + access->size);
+
+      poly_int64 poffset, psize, pmax_size;
+      bool reverse;
+      tree base = get_ref_base_and_extent (access->expr, &poffset, &psize,
+					   &pmax_size, &reverse);
+      HOST_WIDE_INT offset, size, max_size;
+      if (!poffset.is_constant (&offset)
+	  || !psize.is_constant (&size)
+	  || !pmax_size.is_constant (&max_size))
+	gcc_unreachable ();
+      gcc_assert (base == first_base);
+      gcc_assert (offset == access->offset);
+      gcc_assert (access->grp_unscalarizable_region
+		  || size == max_size);
+      gcc_assert (max_size == access->size);
+      gcc_assert (reverse == access->reverse);
+
+      if (access->first_child)
+	{
+	  gcc_assert (access->first_child->parent == access);
+	  access = access->first_child;
+	}
+      else if (access->next_sibling)
+	{
+	  gcc_assert (access->next_sibling->parent == access->parent);
+	  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);
+}
+
+/* Verify access forests of all candidates with accesses by calling
+   verify_access_forest on each on them.  */
+
+DEBUG_FUNCTION void
+verify_all_sra_access_forests (void)
+{
+  bitmap_iterator bi;
+  unsigned i;
+  EXECUTE_IF_SET_IN_BITMAP (candidate_bitmap, 0, i, bi)
+    {
+      tree var = candidate (i);
+      struct access *access = get_first_repr_for_decl (var);
+      if (access)
+	{
+	  gcc_assert (access->base == var);
+	  verify_sra_access_forest (access);
+	}
+    }
+}
+
 /* Return true if expr contains some ARRAY_REFs into a variable bounded
    array.  */
 
@@ -2566,6 +2648,7 @@ create_artificial_child_access (struct access *parent, struct access *model,
   access->offset = new_offset;
   access->size = model->size;
   access->type = model->type;
+  access->parent = parent;
   access->grp_write = set_grp_write;
   access->grp_read = false;
   access->reverse = model->reverse;
@@ -2850,6 +2933,9 @@ analyze_all_variable_accesses (void)
 
   propagate_all_subaccesses ();
 
+  if (flag_checking)
+    verify_all_sra_access_forests ();
+
   bitmap_copy (tmp, candidate_bitmap);
   EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, bi)
     {
-- 
2.24.1