File-copy from v4.4.100
This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
new file mode 100644
index 0000000..2661fad
--- /dev/null
+++ b/arch/x86/lib/memset_64.S
@@ -0,0 +1,138 @@
+/* Copyright 2002 Andi Kleen, SuSE Labs */
+
+#include <linux/linkage.h>
+#include <asm/cpufeature.h>
+#include <asm/alternative-asm.h>
+
+.weak memset
+
+/*
+ * 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
+ * simpler and shorter than the orignal function as well.
+ *
+ * rdi destination
+ * rsi value (char)
+ * rdx count (bytes)
+ *
+ * rax original destination
+ */
+ENTRY(memset)
+ENTRY(__memset)
+ /*
+ * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
+ * to use it when possible. If not available, use fast string instructions.
+ *
+ * Otherwise, use original memset function.
+ */
+ ALTERNATIVE_2 "jmp memset_orig", "", X86_FEATURE_REP_GOOD, \
+ "jmp memset_erms", X86_FEATURE_ERMS
+
+ movq %rdi,%r9
+ movq %rdx,%rcx
+ andl $7,%edx
+ shrq $3,%rcx
+ /* expand byte value */
+ movzbl %sil,%esi
+ movabs $0x0101010101010101,%rax
+ imulq %rsi,%rax
+ rep stosq
+ movl %edx,%ecx
+ rep stosb
+ movq %r9,%rax
+ ret
+ENDPROC(memset)
+ENDPROC(__memset)
+
+/*
+ * ISO C memset - set a memory block to a byte value. This function uses
+ * enhanced rep stosb to override the fast string function.
+ * The code is simpler and shorter than the fast string function as well.
+ *
+ * rdi destination
+ * rsi value (char)
+ * rdx count (bytes)
+ *
+ * rax original destination
+ */
+ENTRY(memset_erms)
+ movq %rdi,%r9
+ movb %sil,%al
+ movq %rdx,%rcx
+ rep stosb
+ movq %r9,%rax
+ ret
+ENDPROC(memset_erms)
+
+ENTRY(memset_orig)
+ movq %rdi,%r10
+
+ /* expand byte value */
+ movzbl %sil,%ecx
+ movabs $0x0101010101010101,%rax
+ imulq %rcx,%rax
+
+ /* align dst */
+ movl %edi,%r9d
+ andl $7,%r9d
+ jnz .Lbad_alignment
+.Lafter_bad_alignment:
+
+ movq %rdx,%rcx
+ shrq $6,%rcx
+ jz .Lhandle_tail
+
+ .p2align 4
+.Lloop_64:
+ decq %rcx
+ movq %rax,(%rdi)
+ movq %rax,8(%rdi)
+ movq %rax,16(%rdi)
+ movq %rax,24(%rdi)
+ movq %rax,32(%rdi)
+ movq %rax,40(%rdi)
+ movq %rax,48(%rdi)
+ movq %rax,56(%rdi)
+ leaq 64(%rdi),%rdi
+ jnz .Lloop_64
+
+ /* Handle tail in loops. The loops should be faster than hard
+ to predict jump tables. */
+ .p2align 4
+.Lhandle_tail:
+ movl %edx,%ecx
+ andl $63&(~7),%ecx
+ jz .Lhandle_7
+ shrl $3,%ecx
+ .p2align 4
+.Lloop_8:
+ decl %ecx
+ movq %rax,(%rdi)
+ leaq 8(%rdi),%rdi
+ jnz .Lloop_8
+
+.Lhandle_7:
+ andl $7,%edx
+ jz .Lende
+ .p2align 4
+.Lloop_1:
+ decl %edx
+ movb %al,(%rdi)
+ leaq 1(%rdi),%rdi
+ jnz .Lloop_1
+
+.Lende:
+ movq %r10,%rax
+ ret
+
+.Lbad_alignment:
+ cmpq $7,%rdx
+ jbe .Lhandle_7
+ movq %rax,(%rdi) /* unaligned store */
+ movq $8,%r8
+ subq %r9,%r8
+ addq %r8,%rdi
+ subq %r8,%rdx
+ jmp .Lafter_bad_alignment
+.Lfinal:
+ENDPROC(memset_orig)