New patch to review for coreboot: 3d2b4f9 libpayload: Reorder default memcpy, speed up memset and memcmp

[Marc Jones]

Marc Jones ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/8126

-gerrit

commit 3d2b4f917024a9924556e0f8c93a180ff028d609
Author: Julius Werner 
Date:   Thu Jun 12 10:28:57 2014 -0700

libpayload: Reorder default memcpy, speed up memset and memcmp

The current default memcpy first copies single bytes to align the
    amount, then copies the rest as full words. In practice, the start of a
    buffer is much more likely to be word-aligned then the end, and aligned
    word access are usually more efficient. This patch reorders those
    accesses to first copy as many full words as possible and then finish
    the rest with byte accesses to optimize this common case.

This fixes a data abort when using USB on ARM without CONFIG_GPL. Due to
    some limitations of how DMA memory is set up in coreboot on ARM, it
    currently does not support unaligned accesses. (This could be fixed with
    a more complicated patch, but it's usually not an issue... unless, of
    course, your memcpy happens to be braindead).

Also add word-aligned accesses to memset and memcmp while I'm at it, and
    make memcmp's return value standard's compliant.

BUG=chrome-os-partner:24957
    TEST=Manual

Original-Change-Id: I2a7bcb35626a05a9a43fcfd99eb958b485d7622a
    Original-Signed-off-by: Julius Werner 
    Original-Reviewed-on: https://chromium-review.googlesource.com/203547
    Original-Reviewed-by: Stefan Reinauer 
    Original-Reviewed-by: David Hendricks 
    (cherry picked from commit 05a64d2e107e1675cc3442e6dabe14a341e55673)
    Signed-off-by: Marc Jones

Change-Id: I0030ca8a203c97587b0da31a0a5e9e11b0be050f
---
 payloads/libpayload/libc/memory.c | 63 +++++++++++++++++++++++++--------------
 1 file changed, 40 insertions(+), 23 deletions(-)

diff --git a/payloads/libpayload/libc/memory.c b/payloads/libpayload/libc/memory.c
index 12d7e33..aec60e4 100644
--- a/payloads/libpayload/libc/memory.c
+++ b/payloads/libpayload/libc/memory.c
@@ -35,12 +35,22 @@

static void *default_memset(void *s, int c, size_t n)
 {
-	char *os = s;
+	size_t i;
+	void *ret = s;
+	unsigned long w = c & 0xff;

-	while (n--)
-		*(os++) = c;
+	for (i = 1; i < sizeof(unsigned long); i <<= 1)
+		w = (w << (i * 8)) | w;

-	return s;
+	for (i = 0; i < n / sizeof(unsigned long); i++)
+		((unsigned long *)s)[i] = w;
+
+	s += i * sizeof(unsigned long);
+
+	for (i = 0; i < n % sizeof(unsigned long); i++)
+		((u8 *)s)[i] = (u8)c;
+
+	return ret;
 }

void *memset(void *s, int c, size_t n)
@@ -48,18 +58,17 @@ void *memset(void *s, int c, size_t n)

static void *default_memcpy(void *dst, const void *src, size_t n)
 {
-	int i;
+	size_t i;
    void *ret = dst;

-	for(i = 0; i < n % sizeof(unsigned long); i++)
-		((unsigned char *) dst)[i] = ((unsigned char *) src)[i];
+	for(i = 0; i < n / sizeof(unsigned long); i++)
+		((unsigned long *)dst)[i] = ((unsigned long *)src)[i];

-	n -= i;
-	src += i;
-	dst += i;
+	src += i * sizeof(unsigned long);
+	dst += i * sizeof(unsigned long);

-	for(i = 0; i < n / sizeof(unsigned long); i++)
-		((unsigned long *) dst)[i] = ((unsigned long *) src)[i];
+	for(i = 0; i < n % sizeof(unsigned long); i++)
+		((u8 *)dst)[i] = ((u8 *)src)[i];

return ret;
 }
@@ -69,8 +78,7 @@ void *memcpy(void *dst, const void *src, size_t n)

static void *default_memmove(void *dst, const void *src, size_t n)
 {
-	int i;
-	unsigned long offs;
+	size_t i, offs;

if (src > dst)
    	return memcpy(dst, src, n);
@@ -78,8 +86,7 @@ static void *default_memmove(void *dst, const void *src, size_t n)
    offs = n - (n % sizeof(unsigned long));

for (i = (n % sizeof(unsigned long)) - 1; i >= 0; i--)
-		((unsigned char *)dst)[i + offs] =
-			((unsigned char *)src)[i + offs];
+		((u8 *)dst)[i + offs] = ((u8 *)src)[i + offs];

for (i = n / sizeof(unsigned long) - 1; i >= 0; i--)
    	((unsigned long *)dst)[i] = ((unsigned long *)src)[i];
@@ -95,17 +102,27 @@ void *memmove(void *dst, const void *src, size_t n)
  *
  * @param s1 Pointer to the first area to compare.
  * @param s2 Pointer to the second area to compare.
- * @param len Size of the first area in bytes (both must have the same length).
- * @return If len is 0, return zero. If the areas match, return zero.
- *         Otherwise return non-zero.
+ * @param n Size of the first area in bytes (both must have the same length).
+ * @return If n is 0, return zero. Otherwise, return a value less than, equal
+ * 	   to, or greater than zero if s1 is found less than, equal to, or
+ * 	   greater than s2 respectively.
  */

-static int default_memcmp(const void *s1, const void *s2, size_t len)
+static int default_memcmp(const void *s1, const void *s2, size_t n)
 {
-	for (; len && *(char *)s1++ == *(char *)s2++; len--) ;
-	return len;
+	size_t i;
+
+	for (i = 0; i < n / sizeof(unsigned long); i++)
+		if (((unsigned long *)s1)[i] != ((unsigned long *)s2)[i])
+			break;	/* fall through to find differing byte */
+
+	for (i *= sizeof(unsigned long); i < n; i++)
+		if (((u8 *)s1)[i] != ((u8 *)s2)[i])
+			return ((u8 *)s1)[i] - ((u8 *)s2)[i];
+
+	return 0;
 }

-int memcmp(const void *s1, const void *s2, size_t len)
+int memcmp(const void *s1, const void *s2, size_t n)
    __attribute__((weak, alias("default_memcmp")));