diff -Naurp gcc/config/avr/avr-devices.c gcc/config/avr/avr-devices.c
--- gcc/config/avr/avr-devices.c	2011-10-28 14:39:27.000000000 +0530
+++ gcc/config/avr/avr-devices.c	2011-10-28 14:59:12.000000000 +0530
@@ -278,6 +278,7 @@ const struct mcu_type_s avr_mcu_types[] 
   { "avrxmega4",    ARCH_AVRXMEGA4, NULL,                           0, 0x2000, "x64d3" },
   { "atxmega64a3",  ARCH_AVRXMEGA4, "__AVR_ATxmega64A3__",          0, 0x2000, "x64a3" },
   { "atxmega64a3u", ARCH_AVRXMEGA4, "__AVR_ATxmega64A3U__",         0, 0x2000, "x64a3u"},
+  { "atxmega64a4u", ARCH_AVRXMEGA4, "__AVR_ATxmega64A4U__",         0, 0x2000, "x64a4u"},
   { "atxmega64b1",  ARCH_AVRXMEGA4, "__AVR_ATxmega64B1__",          0, 0x2000, "x64b1" },
   { "atxmega64b3",  ARCH_AVRXMEGA4, "__AVR_ATxmega64B3__",          0, 0x2000, "x64b3"},
   { "atxmega64d3",  ARCH_AVRXMEGA4, "__AVR_ATxmega64D3__",          0, 0x2000, "x64d3" },
diff -Naurp gcc/config/avr/t-avr gcc/config/avr/t-avr
--- gcc/config/avr/t-avr	2011-10-28 14:52:10.000000000 +0530
+++ gcc/config/avr/t-avr	2011-10-28 14:59:12.000000000 +0530
@@ -288,6 +288,7 @@ MULTILIB_MATCHES = \
 	mmcu?avrxmega2=mmcu?atxmega32x1 \
 	mmcu?avrxmega4=mmcu?atxmega64a3 \
 	mmcu?avrxmega4=mmcu?atxmega64a3u \
+	mmcu?avrxmega4=mmcu?atxmega64a4u \
 	mmcu?avrxmega4=mmcu?atxmega64b1 \
 	mmcu?avrxmega4=mmcu?atxmega64b3 \
 	mmcu?avrxmega4=mmcu?atxmega64d3 \