Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c	(revision 241222)
+++ config/i386/i386.c	(working copy)
@@ -50833,6 +50833,9 @@ ix86_addr_space_zero_address_valid (addr
 #undef TARGET_HARD_REGNO_SCRATCH_OK
 #define TARGET_HARD_REGNO_SCRATCH_OK ix86_hard_regno_scratch_ok
 
+#undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
+#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 1
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 #include "gt-i386.h"
Index: config/i386/i386.h
===================================================================
--- config/i386/i386.h	(revision 241222)
+++ config/i386/i386.h	(working copy)
@@ -2666,9 +2666,6 @@ extern void debug_dispatch_window (int);
 
 #define TARGET_SUPPORTS_WIDE_INT 1
 
-/* Use custom descriptors instead of trampolines when possible.  */
-#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 1
-
 /*
 Local variables:
 version-control: t
Index: config/ia64/ia64.c
===================================================================
--- config/ia64/ia64.c	(revision 241222)
+++ config/ia64/ia64.c	(working copy)
@@ -649,6 +649,9 @@ static const struct attribute_spec ia64_
 #undef TARGET_ATTRIBUTE_TAKES_IDENTIFIER_P
 #define TARGET_ATTRIBUTE_TAKES_IDENTIFIER_P ia64_attribute_takes_identifier_p
 
+#undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
+#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 0
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 /* Returns TRUE iff the target attribute indicated by ATTR_ID takes a plain
Index: config/ia64/ia64.h
===================================================================
--- config/ia64/ia64.h	(revision 241222)
+++ config/ia64/ia64.h	(working copy)
@@ -1715,7 +1715,4 @@ struct GTY(()) machine_function
 /* Switch on code for querying unit reservations.  */
 #define CPU_UNITS_QUERY 1
 
-/* IA-64 already uses descriptors for its standard calling sequence.  */
-#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 0
-
 /* End of ia64.h */
Index: config/rs6000/rs6000.c
===================================================================
--- config/rs6000/rs6000.c	(revision 241222)
+++ config/rs6000/rs6000.c	(working copy)
@@ -1867,6 +1867,9 @@ static const struct attribute_spec rs600
 
 #undef TARGET_OPTAB_SUPPORTED_P
 #define TARGET_OPTAB_SUPPORTED_P rs6000_optab_supported_p
+
+#undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
+#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 1
 
 
 /* Processor table.  */
@@ -4862,6 +4865,10 @@ rs6000_option_override_internal (bool gl
 	 Linux and Darwin ABIs at the moment.  For now, only AIX is fixed.  */
       if (DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_DARWIN)
 	targetm.calls.split_complex_arg = NULL;
+
+      /* The AIX and ELFv1 ABIs define standard function descriptors.  */
+      if (DEFAULT_ABI == ABI_AIX)
+	targetm.calls.custom_function_descriptors = 0;
     }
 
   /* Initialize rs6000_cost with the appropriate target costs.  */
Index: config/rs6000/rs6000.h
===================================================================
--- config/rs6000/rs6000.h	(revision 241222)
+++ config/rs6000/rs6000.h	(working copy)
@@ -2922,9 +2922,6 @@ extern GTY(()) tree rs6000_builtin_decls
 
 #define TARGET_SUPPORTS_WIDE_INT 1
 
-/* Use custom descriptors instead of trampolines if not AIX or ELFv1.  */
-#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS (DEFAULT_ABI != ABI_AIX)
-
 #if (GCC_VERSION >= 3000)
 #pragma GCC poison TARGET_FLOAT128 OPTION_MASK_FLOAT128 MASK_FLOAT128
 #endif
Index: config/sparc/sparc.c
===================================================================
--- config/sparc/sparc.c	(revision 241222)
+++ config/sparc/sparc.c	(working copy)
@@ -866,6 +866,9 @@ char sparc_hard_reg_printed[8];
 #undef TARGET_FIXED_CONDITION_CODE_REGS
 #define TARGET_FIXED_CONDITION_CODE_REGS sparc_fixed_condition_code_regs
 
+#undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
+#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 1
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 /* Return the memory reference contained in X if any, zero otherwise.  */
Index: config/sparc/sparc.h
===================================================================
--- config/sparc/sparc.h	(revision 241222)
+++ config/sparc/sparc.h	(working copy)
@@ -1813,6 +1813,3 @@ extern int sparc_indent_opcode;
 #define SPARC_LOW_FE_EXCEPT_VALUES 0
 
 #define TARGET_SUPPORTS_WIDE_INT 1
-
-/* Use custom descriptors instead of trampolines when possible.  */
-#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 1
Index: testsuite/gcc.dg/Wtrampolines.c
===================================================================
--- testsuite/gcc.dg/Wtrampolines.c	(revision 241222)
+++ testsuite/gcc.dg/Wtrampolines.c	(working copy)
@@ -28,7 +28,7 @@ void foo (void)
 
   double a (int k, pfun x1, pfun x2, pfun x3, pfun x4, pfun x5)
   {
-    double b (void)  /* { dg-warning "trampoline generated for nested function 'b'" } */
+    double b (void)  /* { dg-warning "trampoline generated for nested function 'b'" "standard descriptors" { xfail ia64-*-* powerpc64-*-* } } */
     { 
       k = k - 1;
       return a (k, b, x1, x2, x3, x4 );
Index: testsuite/gnat.dg/trampoline4.adb
===================================================================
--- testsuite/gnat.dg/trampoline4.adb	(revision 241222)
+++ testsuite/gnat.dg/trampoline4.adb	(working copy)
@@ -1,6 +1,6 @@
 -- { dg-do compile { target *-*-linux* } }
 -- { dg-options "-ftrampolines -gnatws" }
--- { dg-skip-if "native descriptors" { ia64-*-* powerpc64-*-* } }
+-- { dg-skip-if "standard descriptors" { ia64-*-* powerpc64-*-* } }
 
 procedure Trampoline4 is