Subject: [PATCH] mips: allow the compiler to optimize memset, memcmp, memcpy for better performance and (in some instances) smaller code
From: Felix Fietkau <[email-masked]>

lede-commit: 07e59c7bc7f375f792ec9734be42fe4fa391a8bb
Signed-off-by: Felix Fietkau <[email-masked]>
---
 arch/mips/boot/compressed/Makefile |  3 ++-
 arch/mips/include/asm/string.h     | 38 ++++++++++++++++++++++++++++++++++++++
 arch/mips/lib/Makefile             |  2 +-
 arch/mips/lib/memcmp.c             | 22 ++++++++++++++++++++++
 4 files changed, 63 insertions(+), 2 deletions(-)
 create mode 100644 arch/mips/lib/memcmp.c

--- a/arch/mips/boot/compressed/Makefile
+++ b/arch/mips/boot/compressed/Makefile
@@ -23,7 +23,8 @@ KBUILD_CFLAGS := $(filter-out -pg, $(KBU
 KBUILD_CFLAGS := $(filter-out -fstack-protector, $(KBUILD_CFLAGS))
 
 KBUILD_CFLAGS := $(KBUILD_CFLAGS) -D__KERNEL__ \
-	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) -D"VMLINUX_LOAD_ADDRESS_ULL=$(VMLINUX_LOAD_ADDRESS)ull"
+	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) -D"VMLINUX_LOAD_ADDRESS_ULL=$(VMLINUX_LOAD_ADDRESS)ull" \
+	-D__ZBOOT__
 
 KBUILD_AFLAGS := $(KBUILD_AFLAGS) -D__ASSEMBLY__ \
 	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) \
--- a/arch/mips/include/asm/string.h
+++ b/arch/mips/include/asm/string.h
@@ -19,4 +19,42 @@ extern void *memcpy(void *__to, __const_
 #define __HAVE_ARCH_MEMMOVE
 extern void *memmove(void *__dest, __const__ void *__src, size_t __n);
 
+#ifndef __ZBOOT__
+#define memset(__s, __c, len)					\
+({								\
+	size_t __len = (len);					\
+	void *__ret;						\
+	if (__builtin_constant_p(len) && __len >= 64)		\
+		__ret = memset((__s), (__c), __len);		\
+	else							\
+		__ret = __builtin_memset((__s), (__c), __len);	\
+	__ret;							\
+})
+
+#define memcpy(dst, src, len)					\
+({								\
+	size_t __len = (len);					\
+	void *__ret;						\
+	if (__builtin_constant_p(len) && __len >= 64)		\
+		__ret = memcpy((dst), (src), __len);		\
+	else							\
+		__ret = __builtin_memcpy((dst), (src), __len);	\
+	__ret;							\
+})
+
+#define memmove(dst, src, len)					\
+({								\
+	size_t __len = (len);					\
+	void *__ret;						\
+	if (__builtin_constant_p(len) && __len >= 64)		\
+		__ret = memmove((dst), (src), __len);		\
+	else							\
+		__ret = __builtin_memmove((dst), (src), __len);	\
+	__ret;							\
+})
+
+#define __HAVE_ARCH_MEMCMP
+#define memcmp(src1, src2, len) __builtin_memcmp((src1), (src2), (len))
+#endif
+
 #endif /* _ASM_STRING_H */
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -5,7 +5,7 @@
 
 lib-y	+= bitops.o csum_partial.o delay.o memcpy.o memset.o \
 	   mips-atomic.o strncpy_user.o \
-	   strnlen_user.o uncached.o
+	   strnlen_user.o uncached.o memcmp.o
 
 obj-y			+= iomap_copy.o
 obj-$(CONFIG_PCI)	+= iomap-pci.o
--- /dev/null
+++ b/arch/mips/lib/memcmp.c
@@ -0,0 +1,22 @@
+/*
+ *  copied from linux/lib/string.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+#include <linux/module.h>
+#include <linux/string.h>
+
+#undef memcmp
+int memcmp(const void *cs, const void *ct, size_t count)
+{
+	const unsigned char *su1, *su2;
+	int res = 0;
+
+	for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
+		if ((res = *su1 - *su2) != 0)
+			break;
+	return res;
+}
+EXPORT_SYMBOL(memcmp);
+