Re: [PATCH 2/5] completely_scalarize arrays as well as records.

[Alan Lawrence <alan dot lawrence at arm dot com>]

In-Reply-To: <55E0697D.2010008@arm.com>

On 28/08/15 16:08, Alan Lawrence wrote:
> Alan Lawrence wrote:
>>
>> Right. I think VLA's are the problem with pr64312.C also. I'm testing a fix
>> (that declares arrays with any of these properties as unscalarizable).
> ... 
> In the meantime I've reverted the patch pending further testing on x86, aarch64
> and arm.

I've now tested g++ and fortran (+ bootstrap + check-gcc) on x86, AArch64 and
ARM, and Ada on x86 and ARM.

So far the list of failures from the original patch seems to be:

* g++.dg/torture/pr64312.C on ARM and m68k-linux
* Building Ada on x86
* Ada ACATS c87b31a on ARM (where the Ada frontend builds fine)

Here's a new version, that fixes all the above, by adding a dose of paranoia in
scalarizable_type_p... (I wonder about adding a comment in completely_scalarize
that such cases have already been ruled out?)

OK to install?

Cheers, Alan
---
 gcc/testsuite/gcc.dg/tree-ssa/sra-15.c |  37 ++++++++
 gcc/tree-sra.c                         | 155 +++++++++++++++++++++++----------
 2 files changed, 144 insertions(+), 48 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/sra-15.c

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/sra-15.c b/gcc/testsuite/gcc.dg/tree-ssa/sra-15.c
new file mode 100644
index 0000000..a22062e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/sra-15.c
@@ -0,0 +1,37 @@
+/* Verify that SRA total scalarization works on records containing arrays.  */
+/* { dg-do run } */
+/* { dg-options "-O1 -fdump-tree-release_ssa --param sra-max-scalarization-size-Ospeed=32" } */
+
+extern void abort (void);
+
+struct S
+{
+  char c;
+  unsigned short f[2][2];
+  int i;
+  unsigned short f3, f4;
+};
+
+
+int __attribute__ ((noinline))
+foo (struct S *p)
+{
+  struct S l;
+
+  l = *p;
+  l.i++;
+  l.f[1][0] += 3;
+  *p = l;
+}
+
+int
+main (int argc, char **argv)
+{
+  struct S a = {0, { {5, 7}, {9, 11} }, 4, 0, 0};
+  foo (&a);
+  if (a.i != 5 || a.f[1][0] != 12)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "l;" 0 "release_ssa" } } */
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 8b3a0ad..d9fe058 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -915,73 +915,132 @@ create_access (tree expr, gimple stmt, bool write)
 }
 
 
-/* Return true iff TYPE is a RECORD_TYPE with fields that are either of gimple
-   register types or (recursively) records with only these two kinds of fields.
-   It also returns false if any of these records contains a bit-field.  */
+/* Return true iff TYPE is scalarizable - i.e. a RECORD_TYPE or fixed-length
+   ARRAY_TYPE with fields that are either of gimple register types (excluding
+   bit-fields) or (recursively) scalarizable types.  */
 
 static bool
-type_consists_of_records_p (tree type)
+scalarizable_type_p (tree type)
 {
-  tree fld;
+  gcc_assert (!is_gimple_reg_type (type));
 
-  if (TREE_CODE (type) != RECORD_TYPE)
-    return false;
+  switch (TREE_CODE (type))
+  {
+  case RECORD_TYPE:
+    for (tree fld = TYPE_FIELDS (type); fld; fld = DECL_CHAIN (fld))
+      if (TREE_CODE (fld) == FIELD_DECL)
+	{
+	  tree ft = TREE_TYPE (fld);
 
-  for (fld = TYPE_FIELDS (type); fld; fld = DECL_CHAIN (fld))
-    if (TREE_CODE (fld) == FIELD_DECL)
-      {
-	tree ft = TREE_TYPE (fld);
+	  if (DECL_BIT_FIELD (fld))
+	    return false;
 
-	if (DECL_BIT_FIELD (fld))
-	  return false;
+	  if (!is_gimple_reg_type (ft)
+	      && !scalarizable_type_p (ft))
+	    return false;
+	}
 
-	if (!is_gimple_reg_type (ft)
-	    && !type_consists_of_records_p (ft))
-	  return false;
-      }
+    return true;
 
-  return true;
+  case ARRAY_TYPE:
+    {
+      if (TYPE_DOMAIN (type) == NULL_TREE
+	  || !TREE_CONSTANT (TYPE_MIN_VALUE (TYPE_DOMAIN (type)))
+	  || !TREE_CONSTANT (TYPE_MAX_VALUE (TYPE_DOMAIN (type)))
+	  || !TREE_CONSTANT (TYPE_SIZE (type))
+	  || (tree_to_shwi (TYPE_SIZE (type)) <= 0))
+	return false;
+      tree elem = TREE_TYPE (type);
+      if (DECL_P (elem) && DECL_BIT_FIELD (elem))
+	return false;
+      if (!is_gimple_reg_type (elem)
+	 && !scalarizable_type_p (elem))
+	return false;
+      return true;
+    }
+  default:
+    return false;
+  }
 }
 
-/* Create total_scalarization accesses for all scalar type fields in DECL that
-   must be of a RECORD_TYPE conforming to type_consists_of_records_p.  BASE
-   must be the top-most VAR_DECL representing the variable, OFFSET must be the
-   offset of DECL within BASE.  REF must be the memory reference expression for
-   the given decl.  */
+static void scalarize_elem (tree, HOST_WIDE_INT, HOST_WIDE_INT, 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_record (tree base, tree decl, HOST_WIDE_INT offset,
-			     tree ref)
+completely_scalarize (tree base, tree decl_type, HOST_WIDE_INT offset, tree ref)
 {
-  tree fld, decl_type = TREE_TYPE (decl);
+  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);
 
-  for (fld = TYPE_FIELDS (decl_type); fld; fld = DECL_CHAIN (fld))
-    if (TREE_CODE (fld) == FIELD_DECL)
+	    scalarize_elem (base, pos, tree_to_uhwi (DECL_SIZE (fld)), nref,
+			    ft);
+	  }
+      break;
+    case ARRAY_TYPE:
       {
-	HOST_WIDE_INT pos = offset + int_bit_position (fld);
-	tree ft = TREE_TYPE (fld);
-	tree nref = build3 (COMPONENT_REF, TREE_TYPE (fld), ref, fld,
-			    NULL_TREE);
-
-	if (is_gimple_reg_type (ft))
+	tree elemtype = TREE_TYPE (decl_type);
+	tree elem_size = TYPE_SIZE (elemtype);
+	gcc_assert (elem_size && tree_fits_uhwi_p (elem_size));
+	int el_size = tree_to_uhwi (elem_size);
+	gcc_assert (el_size);
+
+	tree minidx = TYPE_MIN_VALUE (TYPE_DOMAIN (decl_type));
+	tree maxidx = TYPE_MAX_VALUE (TYPE_DOMAIN (decl_type));
+	gcc_assert (TREE_CODE (minidx) == INTEGER_CST
+		    && TREE_CODE (maxidx) == INTEGER_CST);
+	unsigned HOST_WIDE_INT len = tree_to_uhwi (maxidx)
+				     + 1 - tree_to_uhwi (minidx);
+	/* 4th operand to ARRAY_REF is size in units of the type alignment.  */
+	for (unsigned HOST_WIDE_INT idx = 0; idx < len; idx++)
 	  {
-	    struct access *access;
-	    HOST_WIDE_INT size;
-
-	    size = tree_to_uhwi (DECL_SIZE (fld));
-	    access = create_access_1 (base, pos, size);
-	    access->expr = nref;
-	    access->type = ft;
-	    access->grp_total_scalarization = 1;
-	    /* Accesses for intraprocedural SRA can have their stmt NULL.  */
+	    tree t_idx = build_int_cst (TYPE_DOMAIN (decl_type), idx);
+	    tree nref = build4 (ARRAY_REF, elemtype, ref, t_idx, NULL_TREE,
+				NULL_TREE);
+	    int el_off = offset + idx * el_size;
+	    scalarize_elem (base, el_off, el_size, nref, elemtype);
 	  }
-	else
-	  completely_scalarize_record (base, fld, pos, nref);
       }
+      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 and REF must be the reference expression for it.  */
+
+static void
+scalarize_elem (tree base, HOST_WIDE_INT pos, HOST_WIDE_INT size,
+		 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;
+    /* 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 conforming to type_consists_of_records_p.  */
+   RECORD_TYPE or ARRAY_TYPE conforming to scalarizable_type_p.  */
 
 static void
 create_total_scalarization_access (tree var)
@@ -2521,13 +2580,13 @@ analyze_all_variable_accesses (void)
 	tree var = candidate (i);
 
 	if (TREE_CODE (var) == VAR_DECL
-	    && type_consists_of_records_p (TREE_TYPE (var)))
+	    && scalarizable_type_p (TREE_TYPE (var)))
 	  {
 	    if (tree_to_uhwi (TYPE_SIZE (TREE_TYPE (var)))
 		<= max_scalarization_size)
 	      {
 		create_total_scalarization_access (var);
-		completely_scalarize_record (var, var, 0, var);
+		completely_scalarize (var, TREE_TYPE (var), 0, var);
 		if (dump_file && (dump_flags & TDF_DETAILS))
 		  {
 		    fprintf (dump_file, "Will attempt to totally scalarize ");
-- 
1.9.1