calls.c (expand_call): Do not use the target as the return slot if it is not sufficiently aligned.

* calls.c (expand_call): Do not use the target as the return slot if
	it is not sufficiently aligned.

From-SVN: r215958

gcc/ChangeLog

@@ -1,3 +1,8 @@
+2014-10-06  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* calls.c (expand_call): Do not use the target as the return slot if
+	it is not sufficiently aligned.
+
 2014-10-06  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
 
 	* config/rs6000/rs6000.c (analyze_swaps commentary): Add

gcc/calls.c

@@ -2377,7 +2377,14 @@ expand_call (tree exp, rtx target, int ignore)
       {
 	struct_value_size = int_size_in_bytes (rettype);
 
-	if (target && MEM_P (target) && CALL_EXPR_RETURN_SLOT_OPT (exp))
+	/* Even if it is semantically safe to use the target as the return
+	   slot, it may be not sufficiently aligned for the return type.  */
+	if (CALL_EXPR_RETURN_SLOT_OPT (exp)
+	    && target
+	    && MEM_P (target)
+	    && !(MEM_ALIGN (target) < TYPE_ALIGN (rettype)
+		 && SLOW_UNALIGNED_ACCESS (TYPE_MODE (rettype),
+					   MEM_ALIGN (target))))
 	  structure_value_addr = XEXP (target, 0);
 	else
 	  {

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2014-10-06  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gnat.dg/return4.adb: New test.
+	* gnat.dg/return4_pkg.ad[sb]: New helper.
+
 2014-10-06  Edward Smith-Rowland  <3dw4rd@verizon.net>
 
 	* g++.dg/cpp1y/attr-deprecated-neg.C: Attribute no longer ignored.

gcc/testsuite/gnat.dg/return4.adb

@@ -0,0 +1,22 @@
+-- { dg-do run }
+-- { dg-options "-O" }
+
+with Return4_Pkg; use Return4_Pkg;
+
+procedure Return4 is
+
+  type Local_Rec is record
+    C : Character;
+    R : Rec;
+  end record;
+  pragma Pack (Local_Rec);
+
+  L : Local_Rec;
+  for L'Alignment use 2;
+
+begin
+  L.R := Get_Value (0);
+  if L.R.I1 /= 0 then
+    raise Program_Error;
+  end if;
+end;

gcc/testsuite/gnat.dg/return4_pkg.adb

@@ -0,0 +1,9 @@
+package body Return4_Pkg  is
+
+  function Get_Value (I : Integer) return Rec is
+    Value : Rec := (I1 => I, I2 => I, I3 => I);
+  begin
+    return Value;
+  end;
+
+end Return4_Pkg;

gcc/testsuite/gnat.dg/return4_pkg.ads

@@ -0,0 +1,9 @@
+package Return4_Pkg is
+
+  type Rec is record
+    I1, I2, I3 : Integer;
+  end record;
+
+  function Get_Value (I : Integer) return Rec;
+
+end Return4_Pkg;