littlefs: Add littlefs.intrinsics to override intrinsics support

Enables intrinsics for bit operations such as ctz, popc, and le32
conversion. Can be disabled to help debug toolchain issues. Has
proven to be surprisingly useful.

Author: geky

features/filesystem/littlefs/littlefs/lfs_util.h

@@ -46,6 +46,7 @@
 #define MBED_LFS_ENABLE_WARN   true
 #define MBED_LFS_ENABLE_ERROR  true
 #define MBED_LFS_ENABLE_ASSERT true
+#define MBED_LFS_INTRINSICS    true
 #endif
 
 // Logging functions
@@ -106,7 +107,8 @@ static inline uint32_t lfs_min(uint32_t a, uint32_t b) {
 
 // Find the next smallest power of 2 less than or equal to a
 static inline uint32_t lfs_npw2(uint32_t a) {
-#if !defined(LFS_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
+#if !defined(LFS_NO_INTRINSICS) && MBED_LFS_INTRINSICS && \
+    (defined(__GNUC__) || defined(__CC_ARM))
     return 32 - __builtin_clz(a-1);
 #else
     uint32_t r = 0;
@@ -123,7 +125,8 @@ static inline uint32_t lfs_npw2(uint32_t a) {
 // Count the number of trailing binary zeros in a
 // lfs_ctz(0) may be undefined
 static inline uint32_t lfs_ctz(uint32_t a) {
-#if !defined(LFS_NO_INTRINSICS) && defined(__GNUC__)
+#if !defined(LFS_NO_INTRINSICS) && MBED_LFS_INTRINSICS && \
+    defined(__GNUC__)
     return __builtin_ctz(a);
 #else
     return lfs_npw2((a & -a) + 1) - 1;
@@ -132,7 +135,8 @@ static inline uint32_t lfs_ctz(uint32_t a) {
 
 // Count the number of binary ones in a
 static inline uint32_t lfs_popc(uint32_t a) {
-#if !defined(LFS_NO_INTRINSICS) && (defined(__GNUC__) || defined(__CC_ARM))
+#if !defined(LFS_NO_INTRINSICS) && MBED_LFS_INTRINSICS && \
+    (defined(__GNUC__) || defined(__CC_ARM))
     return __builtin_popcount(a);
 #else
     a = a - ((a >> 1) & 0x55555555);
@@ -149,12 +153,12 @@ static inline int lfs_scmp(uint32_t a, uint32_t b) {
 
 // Convert from 32-bit little-endian to native order
 static inline uint32_t lfs_fromle32(uint32_t a) {
-#if !defined(LFS_NO_INTRINSICS) && ( \
+#if !defined(LFS_NO_INTRINSICS) && MBED_LFS_INTRINSICS && ( \
     (defined(  BYTE_ORDER  ) &&   BYTE_ORDER   ==   ORDER_LITTLE_ENDIAN  ) || \
     (defined(__BYTE_ORDER  ) && __BYTE_ORDER   == __ORDER_LITTLE_ENDIAN  ) || \
     (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__))
     return a;
-#elif !defined(LFS_NO_INTRINSICS) && ( \
+#elif !defined(LFS_NO_INTRINSICS) && MBED_LFS_INTRINSICS && ( \
     (defined(  BYTE_ORDER  ) &&   BYTE_ORDER   ==   ORDER_BIG_ENDIAN  ) || \
     (defined(__BYTE_ORDER  ) && __BYTE_ORDER   == __ORDER_BIG_ENDIAN  ) || \
     (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__))

features/filesystem/littlefs/mbed_lib.json

@@ -21,6 +21,11 @@
         "value": 512,
         "help": "Number of blocks to lookahead during block allocation. A larger lookahead reduces the number of passes required to allocate a block. The lookahead buffer requires only 1 bit per block so it can be quite large with little ram impact. Should be a multiple of 32."
     },
+    "intrinsics": {
+        "macro_name": "MBED_LFS_INTRINSICS",
+        "value": true,
+        "help": "Enable intrinsics for bit operations such as ctz, popc, and le32 conversion. Can be disabled to help debug toolchain issues"
+    },
     "enable_info": {
         "macro_name": "MBED_LFS_ENABLE_INFO",
         "value": false,