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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/x86/lib/memmove_64.S
Initial import
Diffstat (limited to 'arch/x86/lib/memmove_64.S')
-rw-r--r--arch/x86/lib/memmove_64.S212
1 files changed, 212 insertions, 0 deletions
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
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+++ b/arch/x86/lib/memmove_64.S
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+/*
+ * Normally compiler builtins are used, but sometimes the compiler calls out
+ * of line code. Based on asm-i386/string.h.
+ *
+ * This assembly file is re-written from memmove_64.c file.
+ * - Copyright 2011 Fenghua Yu <fenghua.yu@intel.com>
+ */
+#include <linux/linkage.h>
+#include <asm/dwarf2.h>
+#include <asm/cpufeature.h>
+#include <asm/alternative-asm.h>
+
+#undef memmove
+
+/*
+ * Implement memmove(). This can handle overlap between src and dst.
+ *
+ * Input:
+ * rdi: dest
+ * rsi: src
+ * rdx: count
+ *
+ * Output:
+ * rax: dest
+ */
+.weak memmove
+
+ENTRY(memmove)
+ENTRY(__memmove)
+ CFI_STARTPROC
+
+ /* Handle more 32 bytes in loop */
+ mov %rdi, %rax
+ cmp $0x20, %rdx
+ jb 1f
+
+ /* Decide forward/backward copy mode */
+ cmp %rdi, %rsi
+ jge .Lmemmove_begin_forward
+ mov %rsi, %r8
+ add %rdx, %r8
+ cmp %rdi, %r8
+ jg 2f
+
+.Lmemmove_begin_forward:
+ ALTERNATIVE "", "movq %rdx, %rcx; rep movsb; retq", X86_FEATURE_ERMS
+
+ /*
+ * movsq instruction have many startup latency
+ * so we handle small size by general register.
+ */
+ cmp $680, %rdx
+ jb 3f
+ /*
+ * movsq instruction is only good for aligned case.
+ */
+
+ cmpb %dil, %sil
+ je 4f
+3:
+ sub $0x20, %rdx
+ /*
+ * We gobble 32 bytes forward in each loop.
+ */
+5:
+ sub $0x20, %rdx
+ movq 0*8(%rsi), %r11
+ movq 1*8(%rsi), %r10
+ movq 2*8(%rsi), %r9
+ movq 3*8(%rsi), %r8
+ leaq 4*8(%rsi), %rsi
+
+ movq %r11, 0*8(%rdi)
+ movq %r10, 1*8(%rdi)
+ movq %r9, 2*8(%rdi)
+ movq %r8, 3*8(%rdi)
+ leaq 4*8(%rdi), %rdi
+ jae 5b
+ addq $0x20, %rdx
+ jmp 1f
+ /*
+ * Handle data forward by movsq.
+ */
+ .p2align 4
+4:
+ movq %rdx, %rcx
+ movq -8(%rsi, %rdx), %r11
+ lea -8(%rdi, %rdx), %r10
+ shrq $3, %rcx
+ rep movsq
+ movq %r11, (%r10)
+ jmp 13f
+.Lmemmove_end_forward:
+
+ /*
+ * Handle data backward by movsq.
+ */
+ .p2align 4
+7:
+ movq %rdx, %rcx
+ movq (%rsi), %r11
+ movq %rdi, %r10
+ leaq -8(%rsi, %rdx), %rsi
+ leaq -8(%rdi, %rdx), %rdi
+ shrq $3, %rcx
+ std
+ rep movsq
+ cld
+ movq %r11, (%r10)
+ jmp 13f
+
+ /*
+ * Start to prepare for backward copy.
+ */
+ .p2align 4
+2:
+ cmp $680, %rdx
+ jb 6f
+ cmp %dil, %sil
+ je 7b
+6:
+ /*
+ * Calculate copy position to tail.
+ */
+ addq %rdx, %rsi
+ addq %rdx, %rdi
+ subq $0x20, %rdx
+ /*
+ * We gobble 32 bytes backward in each loop.
+ */
+8:
+ subq $0x20, %rdx
+ movq -1*8(%rsi), %r11
+ movq -2*8(%rsi), %r10
+ movq -3*8(%rsi), %r9
+ movq -4*8(%rsi), %r8
+ leaq -4*8(%rsi), %rsi
+
+ movq %r11, -1*8(%rdi)
+ movq %r10, -2*8(%rdi)
+ movq %r9, -3*8(%rdi)
+ movq %r8, -4*8(%rdi)
+ leaq -4*8(%rdi), %rdi
+ jae 8b
+ /*
+ * Calculate copy position to head.
+ */
+ addq $0x20, %rdx
+ subq %rdx, %rsi
+ subq %rdx, %rdi
+1:
+ cmpq $16, %rdx
+ jb 9f
+ /*
+ * Move data from 16 bytes to 31 bytes.
+ */
+ movq 0*8(%rsi), %r11
+ movq 1*8(%rsi), %r10
+ movq -2*8(%rsi, %rdx), %r9
+ movq -1*8(%rsi, %rdx), %r8
+ movq %r11, 0*8(%rdi)
+ movq %r10, 1*8(%rdi)
+ movq %r9, -2*8(%rdi, %rdx)
+ movq %r8, -1*8(%rdi, %rdx)
+ jmp 13f
+ .p2align 4
+9:
+ cmpq $8, %rdx
+ jb 10f
+ /*
+ * Move data from 8 bytes to 15 bytes.
+ */
+ movq 0*8(%rsi), %r11
+ movq -1*8(%rsi, %rdx), %r10
+ movq %r11, 0*8(%rdi)
+ movq %r10, -1*8(%rdi, %rdx)
+ jmp 13f
+10:
+ cmpq $4, %rdx
+ jb 11f
+ /*
+ * Move data from 4 bytes to 7 bytes.
+ */
+ movl (%rsi), %r11d
+ movl -4(%rsi, %rdx), %r10d
+ movl %r11d, (%rdi)
+ movl %r10d, -4(%rdi, %rdx)
+ jmp 13f
+11:
+ cmp $2, %rdx
+ jb 12f
+ /*
+ * Move data from 2 bytes to 3 bytes.
+ */
+ movw (%rsi), %r11w
+ movw -2(%rsi, %rdx), %r10w
+ movw %r11w, (%rdi)
+ movw %r10w, -2(%rdi, %rdx)
+ jmp 13f
+12:
+ cmp $1, %rdx
+ jb 13f
+ /*
+ * Move data for 1 byte.
+ */
+ movb (%rsi), %r11b
+ movb %r11b, (%rdi)
+13:
+ retq
+ CFI_ENDPROC
+ENDPROC(__memmove)
+ENDPROC(memmove)