NUVOTON: Re-implement __PC() with toolchain built-in

Re-implement __PC() by replacing BSP assembly with toolchain built-in.

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M2351/device/M2351_funcs.S

@@ -115,3 +115,19 @@ void AssertError(uint8_t * file, uint32_t line)
 }
 #endif
 
+/* Return LR (return address)
+ *
+ * Replace BSP assembly implementation with toolchain built-in (borrow MBED_CALLER_ADDR())
+ */
+uint32_t __PC(void)
+{
+#if (defined(__GNUC__) || defined(__clang__)) && !defined(__CC_ARM)
+    return (uint32_t) __builtin_extract_return_addr(__builtin_return_address(0));
+#elif defined(__CC_ARM)
+    return (uint32_t) __builtin_return_address(0);
+#elif defined(__ICCARM__)
+    return (uint32_t) __get_LR();
+#else
+    #error("__PC() not implemented")
+#endif
+}

targets/TARGET_NUVOTON/TARGET_M2351/device/system_M2351.c

@@ -116,3 +116,19 @@ void AssertError(uint8_t * file, uint32_t line)
 }
 #endif
 
+/* Return LR (return address)
+ *
+ * Replace BSP assembly implementation with toolchain built-in (borrow MBED_CALLER_ADDR())
+ */
+uint32_t __PC(void)
+{
+#if (defined(__GNUC__) || defined(__clang__)) && !defined(__CC_ARM)
+    return (uint32_t) __builtin_extract_return_addr(__builtin_return_address(0));
+#elif defined(__CC_ARM)
+    return (uint32_t) __builtin_return_address(0);
+#elif defined(__ICCARM__)
+    return (uint32_t) __get_LR();
+#else
+    #error("__PC() not implemented")
+#endif
+}