expr.c (target_align): New function.

* expr.c (target_align): New function.  Alignment the TARGET of an
	assignment may be assume to have.
	(highest_pow2_factor_for_target): Use it instead of relying on
	immediate tree attributes of TARGET, not necessarily honored when
	intermediate bitfields are involved.

	testsuite/
	* gcc.c-torture/execute/align-nest.c: New testcase.
	* gnat.dg/misaligned_nest.adb: New testcase.


Co-Authored-By: Eric Botcazou <ebotcazou@adacore.com>

From-SVN: r147916

gcc/ChangeLog

@@ -1,3 +1,11 @@
+2009-05-28  Olivier Hainque  <hainque@adacore.com>
+
+	* expr.c (target_align): New function.  Alignment the TARGET of an
+	assignment may be assume to have.
+	(highest_pow2_factor_for_target): Use it instead of relying on
+	immediate tree attributes of TARGET, not necessarily honored when
+	intermediate bitfields are involved.
+	
 2009-05-27  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR target/40266

gcc/expr.c

@@ -6224,6 +6224,45 @@ component_ref_field_offset (tree exp)
   else
     return SUBSTITUTE_PLACEHOLDER_IN_EXPR (DECL_FIELD_OFFSET (field), exp);
 }
+
+/* Alignment in bits the TARGET of an assignment may be assumed to have.  */
+
+static unsigned HOST_WIDE_INT
+target_align (const_tree target)
+{
+  /* We might have a chain of nested references with intermediate misaligning
+     bitfields components, so need to recurse to find out.  */
+
+  unsigned HOST_WIDE_INT this_align, outer_align;
+
+  switch (TREE_CODE (target))
+    {
+    case BIT_FIELD_REF:
+      return 1;
+
+    case COMPONENT_REF:
+      this_align = DECL_ALIGN (TREE_OPERAND (target, 1));
+      outer_align = target_align (TREE_OPERAND (target, 0));
+      return MIN (this_align, outer_align);
+
+    case ARRAY_REF:
+    case ARRAY_RANGE_REF:
+      this_align = TYPE_ALIGN (TREE_TYPE (target));
+      outer_align = target_align (TREE_OPERAND (target, 0));
+      return MIN (this_align, outer_align);
+
+    CASE_CONVERT:
+    case NON_LVALUE_EXPR:
+    case VIEW_CONVERT_EXPR:
+      this_align = TYPE_ALIGN (TREE_TYPE (target));
+      outer_align = target_align (TREE_OPERAND (target, 0));
+      return MAX (this_align, outer_align);
+
+    default:
+      return TYPE_ALIGN (TREE_TYPE (target));
+    }
+}
+
 
 /* Given an rtx VALUE that may contain additions and multiplications, return
    an equivalent value that just refers to a register, memory, or constant.
@@ -6670,14 +6709,10 @@ highest_pow2_factor (const_tree exp)
 static unsigned HOST_WIDE_INT
 highest_pow2_factor_for_target (const_tree target, const_tree exp)
 {
-  unsigned HOST_WIDE_INT target_align, factor;
+  unsigned HOST_WIDE_INT talign = target_align (target) / BITS_PER_UNIT;
+  unsigned HOST_WIDE_INT factor = highest_pow2_factor (exp);
   
-  factor = highest_pow2_factor (exp);
-  if (TREE_CODE (target) == COMPONENT_REF)
-    target_align = DECL_ALIGN_UNIT (TREE_OPERAND (target, 1));
-  else
-    target_align = TYPE_ALIGN_UNIT (TREE_TYPE (target));
-  return MAX (factor, target_align);
+  return MAX (factor, talign);
 }
 
 /* Return &VAR expression for emulated thread local VAR.  */

gcc/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2009-05-28  Olivier Hainque  <hainque@adacore.com>	
+            Eric Botcazou  <botcazou@adacore.com>
+    
+	* gcc.c-torture/execute/align-nest.c: New testcase.
+	* gnat.dg/misaligned_nest.adb: New testcase.
+
 2009-05-27  Rafael Avila de Espindola  <espindola@google.com>
 
 	* g++.dg/plugin/attribute_plugin.c: Include gcc-plugin.h first.

gcc/testsuite/gcc.c-torture/execute/align-nest.c

@@ -0,0 +1,28 @@
+
+void foo(int n)
+{
+  typedef struct
+  {
+    int value;
+  } myint;
+  
+  struct S
+  {
+    int i[n];
+    unsigned int b:1;
+    myint mi;
+  } __attribute__ ((packed)) __attribute__ ((aligned (4)));
+
+  struct S s[2];
+  int k;
+  
+  for (k = 0; k < 2; k ++)
+    s[k].mi.value = 0;
+}
+
+int main ()
+{
+  foo (2);
+  return 0;
+}
+

gcc/testsuite/gnat.dg/misaligned_nest.adb

@@ -0,0 +1,26 @@
+-- { dg-do run }
+-- { dg-options "-gnatp" }
+
+procedure Misaligned_Nest is
+
+   type Int is record
+      V : Integer;
+   end record;
+
+   type Block is record
+      B : Boolean;
+      I : Int;
+   end record;
+   pragma Pack (Block);
+   for Block'Alignment use 1;
+
+   type Pair is array (1 .. 2) of Block;
+
+   P : Pair;
+begin
+   for K in P'Range loop
+      P(K).I.V := 1;
+   end loop;
+end;
+
+