Index: gcc/machmode.h
===================================================================
--- gcc/machmode.h	2017-10-23 16:52:20.675923636 +0100
+++ gcc/machmode.h	2017-10-23 17:00:49.664349224 +0100
@@ -685,6 +685,17 @@ fixed_size_mode::includes_p (machine_mod
   return true;
 }
 
+/* Wrapper for mode arguments to target macros, so that if a target
+   doesn't need polynomial-sized modes, its header file can continue
+   to treat everything as fixed_size_mode.  This should go away once
+   macros are moved to target hooks.  It shouldn't be used in other
+   contexts.  */
+#if NUM_POLY_INT_COEFFS == 1
+#define MACRO_MODE(MODE) (as_a <fixed_size_mode> (MODE))
+#else
+#define MACRO_MODE(MODE) (MODE)
+#endif
+
 extern opt_machine_mode mode_for_size (unsigned int, enum mode_class, int);
 
 /* Return the machine mode to use for a MODE_INT of SIZE bits, if one
Index: gcc/addresses.h
===================================================================
--- gcc/addresses.h	2017-10-23 16:52:20.675923636 +0100
+++ gcc/addresses.h	2017-10-23 17:00:49.663350133 +0100
@@ -31,14 +31,15 @@ base_reg_class (machine_mode mode ATTRIB
 		enum rtx_code index_code ATTRIBUTE_UNUSED)
 {
 #ifdef MODE_CODE_BASE_REG_CLASS
-  return MODE_CODE_BASE_REG_CLASS (mode, as, outer_code, index_code);
+  return MODE_CODE_BASE_REG_CLASS (MACRO_MODE (mode), as, outer_code,
+				   index_code);
 #else
 #ifdef MODE_BASE_REG_REG_CLASS
   if (index_code == REG)
-    return MODE_BASE_REG_REG_CLASS (mode);
+    return MODE_BASE_REG_REG_CLASS (MACRO_MODE (mode));
 #endif
 #ifdef MODE_BASE_REG_CLASS
-  return MODE_BASE_REG_CLASS (mode);
+  return MODE_BASE_REG_CLASS (MACRO_MODE (mode));
 #else
   return BASE_REG_CLASS;
 #endif
@@ -58,15 +59,15 @@ ok_for_base_p_1 (unsigned regno ATTRIBUT
 		 enum rtx_code index_code ATTRIBUTE_UNUSED)
 {
 #ifdef REGNO_MODE_CODE_OK_FOR_BASE_P
-  return REGNO_MODE_CODE_OK_FOR_BASE_P (regno, mode, as,
+  return REGNO_MODE_CODE_OK_FOR_BASE_P (regno, MACRO_MODE (mode), as,
 					outer_code, index_code);
 #else
 #ifdef REGNO_MODE_OK_FOR_REG_BASE_P
   if (index_code == REG)
-    return REGNO_MODE_OK_FOR_REG_BASE_P (regno, mode);
+    return REGNO_MODE_OK_FOR_REG_BASE_P (regno, MACRO_MODE (mode));
 #endif
 #ifdef REGNO_MODE_OK_FOR_BASE_P
-  return REGNO_MODE_OK_FOR_BASE_P (regno, mode);
+  return REGNO_MODE_OK_FOR_BASE_P (regno, MACRO_MODE (mode));
 #else
   return REGNO_OK_FOR_BASE_P (regno);
 #endif
Index: gcc/targhooks.c
===================================================================
--- gcc/targhooks.c	2017-10-23 17:00:20.920834919 +0100
+++ gcc/targhooks.c	2017-10-23 17:00:49.664349224 +0100
@@ -941,7 +941,7 @@ default_libcall_value (machine_mode mode
 		       const_rtx fun ATTRIBUTE_UNUSED)
 {
 #ifdef LIBCALL_VALUE
-  return LIBCALL_VALUE (mode);
+  return LIBCALL_VALUE (MACRO_MODE (mode));
 #else
   gcc_unreachable ();
 #endif
@@ -1071,11 +1071,13 @@ default_secondary_reload (bool in_p ATTR
     }
 #ifdef SECONDARY_INPUT_RELOAD_CLASS
   if (in_p)
-    rclass = SECONDARY_INPUT_RELOAD_CLASS (reload_class, reload_mode, x);
+    rclass = SECONDARY_INPUT_RELOAD_CLASS (reload_class,
+					   MACRO_MODE (reload_mode), x);
 #endif
 #ifdef SECONDARY_OUTPUT_RELOAD_CLASS
   if (! in_p)
-    rclass = SECONDARY_OUTPUT_RELOAD_CLASS (reload_class, reload_mode, x);
+    rclass = SECONDARY_OUTPUT_RELOAD_CLASS (reload_class,
+					    MACRO_MODE (reload_mode), x);
 #endif
   if (rclass != NO_REGS)
     {
@@ -1603,7 +1605,7 @@ default_memory_move_cost (machine_mode m
 #ifndef MEMORY_MOVE_COST
     return (4 + memory_move_secondary_cost (mode, (enum reg_class) rclass, in));
 #else
-    return MEMORY_MOVE_COST (mode, (enum reg_class) rclass, in);
+    return MEMORY_MOVE_COST (MACRO_MODE (mode), (enum reg_class) rclass, in);
 #endif
 }
 
@@ -1618,7 +1620,8 @@ default_register_move_cost (machine_mode
 #ifndef REGISTER_MOVE_COST
   return 2;
 #else
-  return REGISTER_MOVE_COST (mode, (enum reg_class) from, (enum reg_class) to);
+  return REGISTER_MOVE_COST (MACRO_MODE (mode),
+			     (enum reg_class) from, (enum reg_class) to);
 #endif
 }
 
@@ -1807,7 +1810,8 @@ default_class_max_nregs (reg_class_t rcl
 			 machine_mode mode ATTRIBUTE_UNUSED)
 {
 #ifdef CLASS_MAX_NREGS
-  return (unsigned char) CLASS_MAX_NREGS ((enum reg_class) rclass, mode);
+  return (unsigned char) CLASS_MAX_NREGS ((enum reg_class) rclass,
+					  MACRO_MODE (mode));
 #else
   return ((GET_MODE_SIZE (mode) + UNITS_PER_WORD - 1) / UNITS_PER_WORD);
 #endif
