commit ed0241d122fc56ab60599ef0addac66c303e569b
Author: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Date:   Sat Apr 22 02:29:37 2017 +0100

    arm implementation for fix for PR77728
    
    fixup missing bits
    
    fixup changes

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index f3a6b64b168..ec1f5f450c0 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -79,9 +79,18 @@ struct four_ints
   int i[4];
 };
 
+struct arm_dbl_word_alignment
+{
+  /* Double word alignment is required for argument passing.  */
+  bool dwa_needed;
+  /* Warn if double word alignment was thought to be required because
+     of the issue from PR77728.  */
+  bool wdwa_needed;
+};
+
 /* Forward function declarations.  */
 static bool arm_const_not_ok_for_debug_p (rtx);
-static bool arm_needs_doubleword_align (machine_mode, const_tree);
+static struct arm_dbl_word_alignment arm_needs_doubleword_align (machine_mode, const_tree);
 static int arm_compute_static_chain_stack_bytes (void);
 static arm_stack_offsets *arm_get_frame_offsets (void);
 static void arm_add_gc_roots (void);
@@ -6349,7 +6358,9 @@ aapcs_layout_arg (CUMULATIVE_ARGS *pcum, machine_mode mode,
   /* C3 - For double-word aligned arguments, round the NCRN up to the
      next even number.  */
   ncrn = pcum->aapcs_ncrn;
-  if ((ncrn & 1) && arm_needs_doubleword_align (mode, type))
+  struct arm_dbl_word_alignment res = arm_needs_doubleword_align (mode,
+								  type);
+  if ((ncrn & 1) && res.dwa_needed)
     ncrn++;
 
   nregs = ARM_NUM_REGS2(mode, type);
@@ -6456,26 +6467,53 @@ arm_init_cumulative_args (CUMULATIVE_ARGS *pcum, tree fntype,
 }
 
 /* Return true if mode/type need doubleword alignment.  */
-static bool
+static struct arm_dbl_word_alignment
 arm_needs_doubleword_align (machine_mode mode, const_tree type)
 {
+  struct arm_dbl_word_alignment a = { false, false};
+
   if (!type)
-    return PARM_BOUNDARY < GET_MODE_ALIGNMENT (mode);
+    {
+      a.dwa_needed = PARM_BOUNDARY < GET_MODE_ALIGNMENT (mode);
+      return a;
+    }
 
   /* Scalar and vector types: Use natural alignment, i.e. of base type.  */
   if (!AGGREGATE_TYPE_P (type))
-    return TYPE_ALIGN (TYPE_MAIN_VARIANT (type)) > PARM_BOUNDARY;
+    {
+      a.dwa_needed = TYPE_ALIGN (TYPE_MAIN_VARIANT (type)) > PARM_BOUNDARY;
+      return a;
+    }
 
   /* Array types: Use member alignment of element type.  */
   if (TREE_CODE (type) == ARRAY_TYPE)
-    return TYPE_ALIGN (TREE_TYPE (type)) > PARM_BOUNDARY;
+    {
+      a.dwa_needed = TYPE_ALIGN (TREE_TYPE (type)) > PARM_BOUNDARY;
+      return a;
+    }
+
+  unsigned int alignment = 0;
+  unsigned int warn_align = 0;
 
   /* Record/aggregate types: Use greatest member alignment of any member.  */ 
   for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
-    if (DECL_ALIGN (field) > PARM_BOUNDARY)
-      return true;
+    {
+      if (DECL_ALIGN (field) > PARM_BOUNDARY)
+	{
+	  if (TREE_CODE (field) == FIELD_DECL)
+	    {
+	      alignment = MAX (alignment, DECL_ALIGN (field));
+	      a.dwa_needed = true;
+	    }
+	  else
+	      warn_align = MAX (warn_align, DECL_ALIGN (field));
+	}
+    }
 
-  return false;
+  if (warn_align > alignment && !a.dwa_needed)
+    a.wdwa_needed = true;
+
+  return a;
 }
 
 
@@ -6532,9 +6570,16 @@ arm_function_arg (cumulative_args_t pcum_v, machine_mode mode,
     }
 
   /* Put doubleword aligned quantities in even register pairs.  */
-  if (pcum->nregs & 1
+  struct arm_dbl_word_alignment res = arm_needs_doubleword_align (mode, type);
+
+  if ((pcum->nregs & 1) && ARM_DOUBLEWORD_ALIGN && res.wdwa_needed && warn_psabi)
+    inform (input_location,
+	    "parameter passing for argument of type %qT changed in GCC 7.1",
+	    type);
+
+  if ((pcum->nregs & 1)
       && ARM_DOUBLEWORD_ALIGN
-      && arm_needs_doubleword_align (mode, type))
+      && res.dwa_needed)
     pcum->nregs++;
 
   /* Only allow splitting an arg between regs and memory if all preceding
@@ -6554,7 +6599,14 @@ arm_function_arg (cumulative_args_t pcum_v, machine_mode mode,
 static unsigned int
 arm_function_arg_boundary (machine_mode mode, const_tree type)
 {
-  return (ARM_DOUBLEWORD_ALIGN && arm_needs_doubleword_align (mode, type)
+  struct arm_dbl_word_alignment res = arm_needs_doubleword_align (mode, type);
+
+  if (ARM_DOUBLEWORD_ALIGN && res.wdwa_needed && warn_psabi)
+    inform (input_location,
+	    "parameter passing for argument of type %qT changed in GCC 7.1",
+	    type);
+
+  return (ARM_DOUBLEWORD_ALIGN && res.dwa_needed
 	  ? DOUBLEWORD_ALIGNMENT
 	  : PARM_BOUNDARY);
 }
@@ -26516,7 +26568,12 @@ arm_setup_incoming_varargs (cumulative_args_t pcum_v,
   if (pcum->pcs_variant <= ARM_PCS_AAPCS_LOCAL)
     {
       nregs = pcum->aapcs_ncrn;
-      if ((nregs & 1) && arm_needs_doubleword_align (mode, type))
+      struct arm_dbl_word_alignment res = arm_needs_doubleword_align (mode,
+								      type);
+      if ((nregs & 1) && res.wdwa_needed && warn_psabi)
+	inform (input_location, "parameter passing for argument of type %qT "
+		"changed in GCC 7.1", type);
+      if ((nregs & 1) && res.dwa_needed)
 	nregs++;
     }
   else