re PR c++/79085 (ICE with placement new to unaligned location)

	PR c++/79085
	* calls.c (expand_call): For TREE_ADDRESSABLE rettype ignore alignment
	check and use address of target always.

	* g++.dg/opt/pr79085.C: New test.

From-SVN: r258574

gcc/ChangeLog

+2018-03-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/79085
+	* calls.c (expand_call): For TREE_ADDRESSABLE rettype ignore alignment
+	check and use address of target always.
+
 2018-03-15  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR target/84574

gcc/calls.c

@@ -3422,9 +3422,14 @@ expand_call (tree exp, rtx target, int ignore)
 	if (CALL_EXPR_RETURN_SLOT_OPT (exp)
 	    && target
 	    && MEM_P (target)
-	    && !(MEM_ALIGN (target) < TYPE_ALIGN (rettype)
-		 && targetm.slow_unaligned_access (TYPE_MODE (rettype),
-						   MEM_ALIGN (target))))
+	    /* If rettype is addressable, we may not create a temporary.
+	       If target is properly aligned at runtime and the compiler
+	       just doesn't know about it, it will work fine, otherwise it
+	       will be UB.  */
+	    && (TREE_ADDRESSABLE (rettype)
+		|| !(MEM_ALIGN (target) < TYPE_ALIGN (rettype)
+		     && targetm.slow_unaligned_access (TYPE_MODE (rettype),
+						       MEM_ALIGN (target)))))
 	  structure_value_addr = XEXP (target, 0);
 	else
 	  {

gcc/testsuite/ChangeLog

+2018-03-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/79085
+	* g++.dg/opt/pr79085.C: New test.
+
 2018-03-15  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR target/84574

gcc/testsuite/g++.dg/opt/pr79085.C

+// PR c++/79085
+// { dg-do compile }
+// { dg-options "-Os" }
+// { dg-additional-options "-mstrict-align" { target { aarch64*-*-* powerpc*-*-linux* powerpc*-*-elf* } } }
+
+void *operator new (__SIZE_TYPE__, void *p) { return p; }
+
+struct S
+{
+  S ();
+  S (const S &);
+  ~S (void);
+  int i;
+};
+
+S foo ();
+
+static char buf [sizeof (S) + 1];
+
+S *
+bar ()
+{
+  return new (buf + 1) S (foo ());
+}