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-rw-r--r--arch/x86_64/lib/memset.S94
1 files changed, 94 insertions, 0 deletions
diff --git a/arch/x86_64/lib/memset.S b/arch/x86_64/lib/memset.S
index 2aa48f2..ad397f2 100644
--- a/arch/x86_64/lib/memset.S
+++ b/arch/x86_64/lib/memset.S
@@ -13,6 +13,98 @@
.p2align 4
memset:
__memset:
+ movq %rdi,%r10
+ movq %rdx,%r11
+
+ /* expand byte value */
+ movzbl %sil,%ecx
+ movabs $0x0101010101010101,%rax
+ mul %rcx /* with rax, clobbers rdx */
+
+ /* align dst */
+ movl %edi,%r9d
+ andl $7,%r9d
+ jnz .Lbad_alignment
+.Lafter_bad_alignment:
+
+ movl %r11d,%ecx
+ shrl $6,%ecx
+ jz .Lhandle_tail
+
+ .p2align 4
+.Lloop_64:
+ decl %ecx
+ 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 %r11d,%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:
+ movl %r11d,%ecx
+ andl $7,%ecx
+ jz .Lende
+ .p2align 4
+.Lloop_1:
+ decl %ecx
+ movb %al,(%rdi)
+ leaq 1(%rdi),%rdi
+ jnz .Lloop_1
+
+.Lende:
+ movq %r10,%rax
+ ret
+
+.Lbad_alignment:
+ cmpq $7,%r11
+ jbe .Lhandle_7
+ movq %rax,(%rdi) /* unaligned store */
+ movq $8,%r8
+ subq %r9,%r8
+ addq %r8,%rdi
+ subq %r8,%r11
+ jmp .Lafter_bad_alignment
+
+ /* Some CPUs run faster using the string instructions.
+ It is also a lot simpler. Use this when possible */
+
+#include <asm/cpufeature.h>
+
+ .section .altinstructions,"a"
+ .align 8
+ .quad memset
+ .quad memset_c
+ .byte X86_FEATURE_REP_GOOD
+ .byte memset_c_end-memset_c
+ .byte memset_c_end-memset_c
+ .previous
+
+ .section .altinstr_replacement,"ax"
+ /* rdi destination
+ * rsi value
+ * rdx count
+ */
+memset_c:
movq %rdi,%r9
movl %edx,%r8d
andl $7,%r8d
@@ -29,3 +121,5 @@ __memset:
stosb
movq %r9,%rax
ret
+memset_c_end:
+ .previous
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