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Subject[PATCH 4/5] -march=native: REP STOSB
Date
If CPU advertises fast REP STOSB, use it.

Inline clear_page() to use only 3 registers across function call
not whole shebang as required by ABI.

Also, tell gcc to use REP STOSB for memset(), this saves terabytes of .text.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
Makefile | 3 +++
arch/x86/boot/compressed/head_64.S | 4 ++++
arch/x86/crypto/sha1_ssse3_asm.S | 7 ++++++-
arch/x86/include/asm/page_64.h | 13 +++++++++++++
arch/x86/lib/Makefile | 2 ++
arch/x86/lib/memset_64.S | 15 +++++++++++++++
scripts/kconfig/cpuid.c | 6 +++++-
scripts/march-native.sh | 1 +
8 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 84abac4c181a..70d91d52ee60 100644
--- a/Makefile
+++ b/Makefile
@@ -593,6 +593,9 @@ endif
ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
KBUILD_CFLAGS += -mmemcpy-strategy=rep_byte:-1:align
endif
+ifdef CONFIG_MARCH_NATIVE_REP_STOSB
+KBUILD_CFLAGS += -mmemset-strategy=rep_byte:-1:align
+endif

ifeq ($(KBUILD_EXTMOD),)
# Read in dependencies to all Kconfig* files, make sure to run
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 20919b4f3133..a7913f5e18b6 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -447,8 +447,12 @@ relocated:
leaq _bss(%rip), %rdi
leaq _ebss(%rip), %rcx
subq %rdi, %rcx
+#ifdef CONFIG_MARCH_NATIVE_REP_STOSB
+ rep stosb
+#else
shrq $3, %rcx
rep stosq
+#endif

/*
* Adjust our own GOT
diff --git a/arch/x86/crypto/sha1_ssse3_asm.S b/arch/x86/crypto/sha1_ssse3_asm.S
index 6204bd53528c..ffa41d7a582a 100644
--- a/arch/x86/crypto/sha1_ssse3_asm.S
+++ b/arch/x86/crypto/sha1_ssse3_asm.S
@@ -94,10 +94,15 @@
SHA1_PIPELINED_MAIN_BODY

# cleanup workspace
- mov $8, %ecx
mov %rsp, %rdi
xor %rax, %rax
+#ifdef CONFIG_MARCH_NATIVE_REP_STOSB
+ mov $64, %ecx
+ rep stosb
+#else
+ mov $8, %ecx
rep stosq
+#endif

mov %rbp, %rsp # deallocate workspace
pop %rbp
diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index c2353661eaf1..b3d275b07624 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -36,6 +36,18 @@ extern unsigned long __phys_addr_symbol(unsigned long);
#define pfn_valid(pfn) ((pfn) < max_pfn)
#endif

+#ifdef CONFIG_MARCH_NATIVE_REP_STOSB
+static __always_inline void clear_page(void *page)
+{
+ uint32_t len = PAGE_SIZE;
+ asm volatile (
+ "rep stosb"
+ : "+D" (page), "+c" (len)
+ : "a" (0)
+ : "memory"
+ );
+}
+#else
void clear_page_orig(void *page);
void clear_page_rep(void *page);
void clear_page_erms(void *page);
@@ -49,6 +61,7 @@ static inline void clear_page(void *page)
"0" (page)
: "memory", "rax", "rcx");
}
+#endif

#ifdef CONFIG_MARCH_NATIVE_REP_MOVSB
static __always_inline void copy_page(void *to, void *from)
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 8f9460bef2ec..6cb356408ebb 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -45,7 +45,9 @@ endif
else
obj-y += iomap_copy_64.o
lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o
+ifneq ($(CONFIG_MARCH_NATIVE_REP_STOSB),y)
lib-y += clear_page_64.o
+endif
ifneq ($(CONFIG_MARCH_NATIVE_REP_MOVSB),y)
lib-y += copy_page_64.o
endif
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 9bc861c71e75..7786d1a65423 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -8,6 +8,20 @@

.weak memset

+#ifdef CONFIG_MARCH_NATIVE_REP_STOSB
+ENTRY(memset)
+ENTRY(__memset)
+ mov %esi, %eax
+ mov %rdi, %rsi
+ mov %rdx, %rcx
+ rep stosb
+ mov %rsi, %rax
+ ret
+ENDPROC(memset)
+ENDPROC(__memset)
+EXPORT_SYMBOL(memset)
+EXPORT_SYMBOL(__memset)
+#else
/*
* ISO C memset - set a memory block to a byte value. This function uses fast
* string to get better performance than the original function. The code is
@@ -140,3 +154,4 @@ ENTRY(memset_orig)
jmp .Lafter_bad_alignment
.Lfinal:
ENDPROC(memset_orig)
+#endif
diff --git a/scripts/kconfig/cpuid.c b/scripts/kconfig/cpuid.c
index 4947f47e7728..ecb285183581 100644
--- a/scripts/kconfig/cpuid.c
+++ b/scripts/kconfig/cpuid.c
@@ -44,6 +44,7 @@ static inline void cpuid2(uint32_t eax0, uint32_t ecx0, uint32_t *eax, uint32_t

static bool popcnt = false;
static bool rep_movsb = false;
+static bool rep_stosb = false;

static uint32_t eax0_max;

@@ -62,8 +63,10 @@ static void intel(void)
cpuid2(7, 0, &eax, &ecx, &edx, &ebx);
// printf("%08x %08x %08x %08x\n", eax, ecx, edx, ebx);

- if (ebx & (1 << 9))
+ if (ebx & (1 << 9)) {
rep_movsb = true;
+ rep_stosb = true;
+ }
}
}

@@ -85,6 +88,7 @@ int main(int argc, char *argv[])
#define _(x) if (streq(opt, #x)) return x ? EXIT_SUCCESS : EXIT_FAILURE
_(popcnt);
_(rep_movsb);
+ _(rep_stosb);
#undef _

return EXIT_FAILURE;
diff --git a/scripts/march-native.sh b/scripts/march-native.sh
index eb52c20c56b4..d3adf0edb2be 100755
--- a/scripts/march-native.sh
+++ b/scripts/march-native.sh
@@ -32,6 +32,7 @@ option() {
if test -x "$CPUID"; then
"$CPUID" popcnt && option "CONFIG_MARCH_NATIVE_POPCNT"
"$CPUID" rep_movsb && option "CONFIG_MARCH_NATIVE_REP_MOVSB"
+ "$CPUID" rep_stosb && option "CONFIG_MARCH_NATIVE_REP_STOSB"
fi

if test ! -f "$AUTOCONF1" -o ! -f "$AUTOCONF2"; then
--
2.13.6
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