DM: added FPU support

Author: deanm1278

boards.txt

@@ -172,7 +172,7 @@ adafruit_metro_m4.build.usb_product="Adafruit Metro M4"
 adafruit_metro_m4.build.usb_manufacturer="Adafruit LLC"
 adafruit_metro_m4.build.board=SAMD_51
 adafruit_metro_m4.build.core=arduino
-adafruit_metro_m4.build.extra_flags=-D__SAMD51J20A__ -D__SAMD51__ {build.usb_flags}
+adafruit_metro_m4.build.extra_flags=-D__SAMD51J20A__ -D__SAMD51__ {build.usb_flags} -D__FPU_USED
 adafruit_metro_m4.build.ldscript=linker_scripts/gcc/flash_with_bootloader.ld
 adafruit_metro_m4.build.openocdscript=openocd_scripts/arduino_zero.cfg
 adafruit_metro_m4.build.variant=metro_m4
@@ -181,3 +181,6 @@ adafruit_metro_m4.build.vid=0x2341
 adafruit_metro_m4.build.pid=0x804d
 adafruit_metro_m4.bootloader.tool=openocd
 adafruit_metro_m4.bootloader.file=metroM4/samdx1_sam_ba.bin
+adafruit_metro_m4.compiler.c.elf.extra_flags=-mfloat-abi=hard -mfpu=fpv4-sp-d16
+adafruit_metro_m4.compiler.c.extra_flags=-mfloat-abi=hard -mfpu=fpv4-sp-d16
+adafruit_metro_m4.compiler.cpp.extra_flags=-mfloat-abi=hard -mfpu=fpv4-sp-d16

cores/arduino/cortex_handlers.c

@@ -480,6 +480,13 @@ void Reset_Handler(void)
       *pDest = 0;
   }
 
+#if defined(__FPU_USED) && defined(__SAMD51__)
+	/* Enable FPU */
+	SCB->CPACR |= (0xFu << 20);
+	__DSB();
+	__ISB();
+#endif
+
   SystemInit();
 
   main();