--- gcc/config/aarch64/aarch64.c.jj	2017-04-24 19:28:02.518970890 +0200
+++ gcc/config/aarch64/aarch64.c	2017-04-25 11:07:55.169532408 +0200
@@ -2256,33 +2256,58 @@ aarch64_vfp_is_call_candidate (cumulativ
 						  NULL);
 }
 
-/* Given MODE and TYPE of a function argument, return the alignment in
+struct aarch64_fn_arg_alignment
+{
+  /* Alignment for FIELD_DECLs in function arguments.  */
+  unsigned int alignment;
+  /* Alignment for decls other than FIELD_DECLs in function arguments.  */
+  unsigned int warn_alignment;
+};
+
+/* Given MODE and TYPE of a function argument, return a pair of alignments in
    bits.  The idea is to suppress any stronger alignment requested by
    the user and opt for the natural alignment (specified in AAPCS64 \S 4.1).
    This is a helper function for local use only.  */
 
-static unsigned int
+static struct aarch64_fn_arg_alignment
 aarch64_function_arg_alignment (machine_mode mode, const_tree type)
 {
+  struct aarch64_fn_arg_alignment aa;
+  aa.alignment = 0;
+  aa.warn_alignment = 0;
+
   if (!type)
-    return GET_MODE_ALIGNMENT (mode);
+    {
+      aa.alignment = GET_MODE_ALIGNMENT (mode);
+      return aa;
+    }
+
   if (integer_zerop (TYPE_SIZE (type)))
-    return 0;
+    return aa;
 
   gcc_assert (TYPE_MODE (type) == mode);
 
   if (!AGGREGATE_TYPE_P (type))
-    return TYPE_ALIGN (TYPE_MAIN_VARIANT (type));
+    {
+      aa.alignment = TYPE_ALIGN (TYPE_MAIN_VARIANT (type));
+      return aa;
+    }
 
   if (TREE_CODE (type) == ARRAY_TYPE)
-    return TYPE_ALIGN (TREE_TYPE (type));
-
-  unsigned int alignment = 0;
+    {
+      aa.alignment = TYPE_ALIGN (TREE_TYPE (type));
+      return aa;
+    }
 
   for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
-    alignment = std::max (alignment, DECL_ALIGN (field));
+    {
+      if (TREE_CODE (field) == FIELD_DECL)
+	aa.alignment = std::max (aa.alignment, DECL_ALIGN (field));
+      else
+	aa.warn_alignment = std::max (aa.warn_alignment, DECL_ALIGN (field));
+    }
 
-  return alignment;
+  return aa;
 }
 
 /* Layout a function argument according to the AAPCS64 rules.  The rule
@@ -2369,24 +2394,35 @@ aarch64_layout_arg (cumulative_args_t pc
      entirely general registers.  */
   if (allocate_ncrn && (ncrn + nregs <= NUM_ARG_REGS))
     {
-      unsigned int alignment = aarch64_function_arg_alignment (mode, type);
 
       gcc_assert (nregs == 0 || nregs == 1 || nregs == 2);
 
       /* C.8 if the argument has an alignment of 16 then the NGRN is
          rounded up to the next even number.  */
-      if (nregs == 2 && alignment == 16 * BITS_PER_UNIT && ncrn % 2)
+      if (nregs == 2 && ncrn % 2)
 	{
-	  ++ncrn;
-	  gcc_assert (ncrn + nregs <= NUM_ARG_REGS);
+	  struct aarch64_fn_arg_alignment aa
+	    = aarch64_function_arg_alignment (mode, type);
+
+	  if (aa.warn_alignment == 16 * BITS_PER_UNIT
+	      && aa.alignment < aa.warn_alignment
+	      && warn_psabi
+	      && currently_expanding_gimple_stmt)
+	    inform (input_location,
+		    "parameter passing for argument of type %qT "
+		    "changed in GCC 7.1", type);
+	  else if (aa.alignment == 16 * BITS_PER_UNIT)
+	    {
+	      ++ncrn;
+	      gcc_assert (ncrn + nregs <= NUM_ARG_REGS);
+	    }
 	}
+
       /* NREGS can be 0 when e.g. an empty structure is to be passed.
          A reg is still generated for it, but the caller should be smart
 	 enough not to use it.  */
       if (nregs == 0 || nregs == 1 || GET_MODE_CLASS (mode) == MODE_INT)
-	{
-	  pcum->aapcs_reg = gen_rtx_REG (mode, R0_REGNUM + ncrn);
-	}
+	pcum->aapcs_reg = gen_rtx_REG (mode, R0_REGNUM + ncrn);
       else
 	{
 	  rtx par;
@@ -2414,7 +2450,10 @@ aarch64_layout_arg (cumulative_args_t pc
      this argument and align the total size if necessary.  */
 on_stack:
   pcum->aapcs_stack_words = size / UNITS_PER_WORD;
-  if (aarch64_function_arg_alignment (mode, type) == 16 * BITS_PER_UNIT)
+  struct aarch64_fn_arg_alignment aa
+    = aarch64_function_arg_alignment (mode, type);
+
+  if (aa.alignment == 16 * BITS_PER_UNIT)
     pcum->aapcs_stack_size = ROUND_UP (pcum->aapcs_stack_size,
 				       16 / UNITS_PER_WORD);
   return;
@@ -2505,13 +2544,17 @@ aarch64_function_arg_regno_p (unsigned r
 static unsigned int
 aarch64_function_arg_boundary (machine_mode mode, const_tree type)
 {
-  unsigned int alignment = aarch64_function_arg_alignment (mode, type);
+  struct aarch64_fn_arg_alignment aa
+    = aarch64_function_arg_alignment (mode, type);
+  aa.alignment = MIN (MAX (aa.alignment, PARM_BOUNDARY), STACK_BOUNDARY);
+  aa.warn_alignment
+    = MIN (MAX (aa.warn_alignment, PARM_BOUNDARY), STACK_BOUNDARY);
+
+  if (warn_psabi && aa.warn_alignment > aa.alignment)
+    inform (input_location, "parameter passing for argument of type %qT "
+	    "changed in GCC 7.1", type);
 
-  if (alignment < PARM_BOUNDARY)
-    alignment = PARM_BOUNDARY;
-  if (alignment > STACK_BOUNDARY)
-    alignment = STACK_BOUNDARY;
-  return alignment;
+  return aa.alignment;
 }
 
 /* For use by FUNCTION_ARG_PADDING (MODE, TYPE).
@@ -10211,7 +10254,9 @@ aarch64_gimplify_va_arg_expr (tree valis
   stack = build3 (COMPONENT_REF, TREE_TYPE (f_stack), unshare_expr (valist),
 		  f_stack, NULL_TREE);
   size = int_size_in_bytes (type);
-  align = aarch64_function_arg_alignment (mode, type) / BITS_PER_UNIT;
+  struct aarch64_fn_arg_alignment aa
+    = aarch64_function_arg_alignment (mode, type);
+  align = aa.alignment / BITS_PER_UNIT;
 
   dw_align = false;
   adjust = 0;
--- gcc/testsuite/g++.dg/abi/pr77728-2.C.jj	2017-04-25 10:54:08.396372117 +0200
+++ gcc/testsuite/g++.dg/abi/pr77728-2.C	2017-04-25 10:52:37.000000000 +0200
@@ -0,0 +1,171 @@
+// { dg-do compile { target { { aarch64-*-* } && c++11 } } }
+// { dg-options "-Wpsabi" }
+
+#include <stdarg.h>
+
+template <int N>
+struct alignas (16) A { char p[16]; };
+
+A<0> v;
+
+template <int N>
+struct B
+{
+  typedef A<N> T;
+  int i, j, k, l;
+};
+
+struct C : public B<0> {};
+struct D {};
+struct E : public D, C {};
+struct F : public B<1> {};
+struct G : public F { static int y alignas (16); };
+struct H : public G {};
+struct I : public D { int z alignas (16); };
+struct J : public D { static int z alignas (16); int i, j, k, l; };
+
+template <int N>
+struct K : public D { typedef A<N> T; int i, j; };
+
+struct L { static int h alignas (16); int i, j, k, l; };
+
+int
+fn1 (int a, B<0> b)	// { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" }
+{
+  return a + b.i;
+}
+
+int
+fn2 (int a, B<1> b)
+{
+  return a + b.i;
+}
+
+int
+fn3 (int a, L b)	// { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" }
+{
+  return a + b.i;
+}
+
+int
+fn4 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, B<0> n, ...)
+// { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" "" { target *-*-* } .-1 }
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn5 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, B<1> n, ...)
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn6 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, C n, ...)
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn7 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, E n, ...)
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn8 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, H n, ...)
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn9 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, I n, ...)
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn10 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, J n, ...)
+// { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" "" { target *-*-* } .-1 }
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn11 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, K<0> n, ...)
+// { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" "" { target *-*-* } .-1 }
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+int
+fn12 (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int k, int l, int m, K<2> n, ...)
+{
+  va_list ap;
+  va_start (ap, n);
+  int x = va_arg (ap, int);
+  va_end (ap);
+  return x;
+}
+
+void
+test ()
+{
+  static B<0> b0;
+  static B<1> b1;
+  static L l;
+  static C c;
+  static E e;
+  static H h;
+  static I i;
+  static J j;
+  static K<0> k0;
+  static K<2> k2;
+  fn1 (1, b0);	// { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" }
+  fn2 (1, b1);
+  fn3 (1, l);	// { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" }
+  fn4 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, b0, 1, 2, 3, 4);
+  // { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" "" { target *-*-* } .-1 }
+  fn5 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, b1, 1, 2, 3, 4);
+  fn6 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, c, 1, 2, 3, 4);
+  fn7 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, e, 1, 2, 3, 4);
+  fn8 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, h, 1, 2, 3, 4);
+  fn9 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, i, 1, 2, 3, 4);
+  fn10 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, j, 1, 2, 3, 4);
+  // { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" "" { target *-*-* } .-1 }
+  fn11 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, k0, 1, 2, 3, 4);
+  // { dg-message "note: parameter passing for argument of type \[^\n\r]* changed in GCC 7\.1" "" { target *-*-* } .-1 }
+  fn12 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, k2, 1, 2, 3, 4);
+}
