ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.asm

   1 ;------------------------------------------------------------------------------
   2 ;
   3 ; CopyMem() worker for ARM
   4 ;
   5 ; This file started out as C code that did 64 bit moves if the buffer was
   6 ; 32-bit aligned, else it does a byte copy. It also does a byte copy for
   7 ; any trailing bytes. It was updated to do 32-byte copies using stm/ldm.
   8 ;
   9 ; Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
  10 ; This program and the accompanying materials
  11 ; are licensed and made available under the terms and conditions of the BSD License
  12 ; which accompanies this distribution.  The full text of the license may be found at
  13 ; http://opensource.org/licenses/bsd-license.php
  14 ;
  15 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  16 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  17 ;
  18 ;------------------------------------------------------------------------------
  19
  20 /**
  21   Copy Length bytes from Source to Destination. Overlap is OK.
  22
  23   This implementation
  24
  25   @param  Destination Target of copy
  26   @param  Source      Place to copy from
  27   @param  Length      Number of bytes to copy
  28
  29   @return Destination
  30
  31
  32 VOID *
  33 EFIAPI
  34 InternalMemCopyMem (
  35   OUT     VOID                      *DestinationBuffer,
  36   IN      CONST VOID                *SourceBuffer,
  37   IN      UINTN                     Length
  38   )
  39 **/
  40
  41     INCLUDE AsmMacroExport.inc
  42
  43  RVCT_ASM_EXPORT InternalMemCopyMem
  44   stmfd  sp!, {r4-r11, lr}
  45   // Save the input parameters in extra registers (r11 = destination, r14 = source, r12 = length)
  46   mov  r11, r0
  47   mov  r10, r0
  48   mov  r12, r2
  49   mov  r14, r1
  50
  51 memcopy_check_overlapped
  52   cmp  r11, r1
  53   // If (dest < source)
  54   bcc  memcopy_check_optim_default
  55   // If (dest <= source). But with the previous condition ->  If (dest == source)
  56   bls  memcopy_end
  57
  58   // If (source + length < dest)
  59   rsb  r3, r1, r11
  60   cmp  r12, r3
  61   bcc  memcopy_check_optim_default
  62
  63   // If (length == 0)
  64   cmp  r12, #0
  65   beq  memcopy_end
  66
  67   b     memcopy_check_optim_overlap
  68
  69 memcopy_check_optim_default
  70   // Check if we can use an optimized path ((length >= 32) && destination word-aligned && source word-aligned) for the memcopy (optimized path if r0 == 1)
  71   tst  r0, #0xF
  72   movne  r0, #0
  73   bne   memcopy_default
  74   tst  r1, #0xF
  75   movne  r3, #0
  76   moveq  r3, #1
  77   cmp  r2, #31
  78   movls  r0, #0
  79   andhi  r0, r3, #1
  80   b     memcopy_default
  81
  82 memcopy_check_optim_overlap
  83   // r10 = dest_end, r14 = source_end
  84   add  r10, r11, r12
  85   add  r14, r12, r1
  86
  87   // Are we in the optimized case ((length >= 32) && dest_end word-aligned && source_end word-aligned)
  88   cmp  r2, #31
  89   movls  r0, #0
  90   movhi  r0, #1
  91   tst  r10, #0xF
  92   movne  r0, #0
  93   tst  r14, #0xF
  94   movne  r0, #0
  95   b  memcopy_overlapped
  96
  97 memcopy_overlapped_non_optim
  98   // We read 1 byte from the end of the source buffer
  99   sub  r3, r14, #1
 100   sub  r12, r12, #1
 101   ldrb  r3, [r3, #0]
 102   sub  r2, r10, #1
 103   cmp  r12, #0
 104   // We write 1 byte at the end of the dest buffer
 105   sub  r10, r10, #1
 106   sub  r14, r14, #1
 107   strb  r3, [r2, #0]
 108   bne  memcopy_overlapped_non_optim
 109   b   memcopy_end
 110
 111 // r10 = dest_end, r14 = source_end
 112 memcopy_overlapped
 113   // Are we in the optimized case ?
 114   cmp  r0, #0
 115   beq  memcopy_overlapped_non_optim
 116
 117   // Optimized Overlapped - Read 32 bytes
 118   sub  r14, r14, #32
 119   sub  r12, r12, #32
 120   cmp  r12, #31
 121   ldmia  r14, {r2-r9}
 122
 123   // If length is less than 32 then disable optim
 124   movls  r0, #0
 125
 126   cmp  r12, #0
 127
 128   // Optimized Overlapped - Write 32 bytes
 129   sub  r10, r10, #32
 130   stmia  r10, {r2-r9}
 131
 132   // while (length != 0)
 133   bne  memcopy_overlapped
 134   b   memcopy_end
 135
 136 memcopy_default_non_optim
 137   // Byte copy
 138   ldrb  r3, [r14], #1
 139   sub  r12, r12, #1
 140   strb  r3, [r10], #1
 141
 142 memcopy_default
 143   cmp  r12, #0
 144   beq  memcopy_end
 145
 146 // r10 = dest, r14 = source
 147 memcopy_default_loop
 148   cmp  r0, #0
 149   beq  memcopy_default_non_optim
 150
 151   // Optimized memcopy - Read 32 Bytes
 152   sub  r12, r12, #32
 153   cmp  r12, #31
 154   ldmia  r14!, {r2-r9}
 155
 156   // If length is less than 32 then disable optim
 157   movls  r0, #0
 158
 159   cmp  r12, #0
 160
 161   // Optimized memcopy - Write 32 Bytes
 162   stmia  r10!, {r2-r9}
 163
 164   // while (length != 0)
 165   bne  memcopy_default_loop
 166
 167 memcopy_end
 168   mov  r0, r11
 169   ldmfd  sp!, {r4-r11, pc}
 170
 171   END
 172