libc: minimal: add size optimized string functions
The current implementations of memcpy and memset are optimized for
performance and use a word based loop before the byte based loop.
Add a config option that skips the word based loop. This saves 120
bytes on the Cortex-M0+ which is worthwhile on small apps like a
bootloader.
Enable by default if SIZE_OPTIMIZATIONS is set.
Signed-off-by: Michael Hope <mlhx@google.com>
diff --git a/lib/libc/minimal/source/string/string.c b/lib/libc/minimal/source/string/string.c
index 20996e4..1f889e9 100644
--- a/lib/libc/minimal/source/string/string.c
+++ b/lib/libc/minimal/source/string/string.c
@@ -301,6 +301,8 @@
unsigned char *d_byte = (unsigned char *)d;
const unsigned char *s_byte = (const unsigned char *)s;
+
+#if !defined(CONFIG_MINIMAL_LIBC_OPTIMIZE_STRING_FOR_SIZE)
const uintptr_t mask = sizeof(mem_word_t) - 1;
if ((((uintptr_t)d ^ (uintptr_t)s_byte) & mask) == 0) {
@@ -328,6 +330,7 @@
d_byte = (unsigned char *)d_word;
s_byte = (unsigned char *)s_word;
}
+#endif
/* do byte-sized copying until finished */
@@ -353,6 +356,7 @@
unsigned char *d_byte = (unsigned char *)buf;
unsigned char c_byte = (unsigned char)c;
+#if !defined(CONFIG_MINIMAL_LIBC_OPTIMIZE_STRING_FOR_SIZE)
while (((uintptr_t)d_byte) & (sizeof(mem_word_t) - 1)) {
if (n == 0) {
return buf;
@@ -380,6 +384,7 @@
/* do byte-sized initialization until finished */
d_byte = (unsigned char *)d_word;
+#endif
while (n > 0) {
*(d_byte++) = c_byte;
