Index: gcc/regrename.h
===================================================================
--- gcc/regrename.h	(revision 224700)
+++ gcc/regrename.h	(working copy)
@@ -91,6 +91,6 @@ extern void regrename_analyze (bitmap);
 extern du_head_p regrename_chain_from_id (unsigned int);
 extern int find_rename_reg (du_head_p, enum reg_class, HARD_REG_SET *, int,
 			    bool);
-extern void regrename_do_replace (du_head_p, int);
+extern bool regrename_do_replace (du_head_p, int);
 
 #endif
Index: gcc/regrename.c
===================================================================
--- gcc/regrename.c	(revision 224700)
+++ gcc/regrename.c	(working copy)
@@ -496,12 +496,20 @@ rename_chains (void)
 	  continue;
 	}
 
-      if (dump_file)
-	fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
-
-      regrename_do_replace (this_head, best_new_reg);
-      tick[best_new_reg] = ++this_tick;
-      df_set_regs_ever_live (best_new_reg, true);
+      if (regrename_do_replace (this_head, best_new_reg))
+	{
+	  if (dump_file)
+	    fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
+	  tick[best_new_reg] = ++this_tick;
+	  df_set_regs_ever_live (best_new_reg, true);
+	}
+      else
+	{
+	  if (dump_file)
+	    fprintf (dump_file, ", renaming as %s failed\n",
+		     reg_names[best_new_reg]);
+	  tick[reg] = ++this_tick;
+	}
     }
 }
 
@@ -927,7 +935,13 @@ regrename_analyze (bitmap bb_mask)
     bb->aux = NULL;
 }
 
-void
+/* Attempt to replace all uses of the register in the chain beginning with
+   HEAD with REG.  Returns true on success and false if the replacement is
+   rejected because the insns would not validate.  The latter can happen
+   e.g. if a match_parallel predicate enforces restrictions on register
+   numbering in its subpatterns.  */
+
+bool
 regrename_do_replace (struct du_head *head, int reg)
 {
   struct du_chain *chain;
@@ -941,22 +955,26 @@ regrename_do_replace (struct du_head *he
       int reg_ptr = REG_POINTER (*chain->loc);
 
       if (DEBUG_INSN_P (chain->insn) && REGNO (*chain->loc) != base_regno)
-	INSN_VAR_LOCATION_LOC (chain->insn) = gen_rtx_UNKNOWN_VAR_LOC ();
+	validate_change (chain->insn, &(INSN_VAR_LOCATION_LOC (chain->insn)),
+			 gen_rtx_UNKNOWN_VAR_LOC (), true);
       else
 	{
-	  *chain->loc = gen_raw_REG (GET_MODE (*chain->loc), reg);
+	  validate_change (chain->insn, chain->loc, 
+			   gen_raw_REG (GET_MODE (*chain->loc), reg), true);
 	  if (regno >= FIRST_PSEUDO_REGISTER)
 	    ORIGINAL_REGNO (*chain->loc) = regno;
 	  REG_ATTRS (*chain->loc) = attr;
 	  REG_POINTER (*chain->loc) = reg_ptr;
 	}
-
-      df_insn_rescan (chain->insn);
     }
 
+  if (!apply_change_group ())
+    return false;
+
   mode = GET_MODE (*head->first->loc);
   head->regno = reg;
   head->nregs = hard_regno_nregs[reg][mode];
+  return true;
 }
 
 
Index: gcc/config/aarch64/cortex-a57-fma-steering.c
===================================================================
--- gcc/config/aarch64/cortex-a57-fma-steering.c	(revision 224700)
+++ gcc/config/aarch64/cortex-a57-fma-steering.c	(working copy)
@@ -288,11 +288,19 @@ rename_single_chain (du_head_p head, HAR
       return false;
     }
 
-  if (dump_file)
-    fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
-
-  regrename_do_replace (head, best_new_reg);
-  df_set_regs_ever_live (best_new_reg, true);
+  if (regrename_do_replace (head, best_new_reg))
+    {
+      if (dump_file)
+	fprintf (dump_file, ", renamed as %s\n", reg_names[best_new_reg]);
+      df_set_regs_ever_live (best_new_reg, true);
+    }
+  else
+    {
+      if (dump_file)
+	fprintf (dump_file, ", renaming as %s failed\n",
+		 reg_names[best_new_reg]);
+      return false;
+    }
   return true;
 }