ArmPkg: Fix InternalMemCopyMem()

    
This function crashed when regions overalapped. The condition to
optimize the copy of overlapped regions was not correct.
    

ArmPkg: Add comments to InternalMemCopyMem()
    
These comments explain the flow of this assembly function.




git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11486 6f19259b-4bc3-4df7-8a09-765794883524

2 files changed, 212 insertions, 94 deletions

diff --git a/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.S b/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.S
index 1298f94e8..4e0122bde 100755
--- a/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.S
+++ b/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.S
@@ -43,70 +43,129 @@ GCC_ASM_EXPORT(InternalMemCopyMem)
 

 ASM_PFX(InternalMemCopyMem):

   stmfd  sp!, {r4-r11, lr}

-  tst  r0, #3

+  // Save the input parameters in extra registers (r11 = destination, r14 = source, r12 = length)

   mov  r11, r0

   mov  r10, r0

-  mov  ip, r2

-  mov  lr, r1

+  mov  r12, r2

+  mov  r14, r1

+  

+memcopy_check_overlapped:

+  cmp  r11, r1

+  // If (dest < source)

+  bcc  memcopy_check_optim_default

+  // If (dest <= source). But with the previous condition ->  If (dest == source)

+  bls  memcopy_end

+

+  // If (source + length < dest)

+  rsb  r3, r1, r11

+  cmp  r12, r3

+  bcc  memcopy_check_optim_default

+

+  // If (length == 0)  

+  cmp  r12, #0

+  beq  memcopy_end

+  

+  b     memcopy_check_optim_overlap

+

+memcopy_check_optim_default:

+  // Check if we can use an optimized path ((length >= 32) && destination word-aligned && source word-aligned) for the memcopy (optimized path if r0 == 1)

+  tst  r0, #0xF

   movne  r0, #0

-  bne  L4

-  tst  r1, #3

+  bne   memcopy_default

+  tst  r1, #0xF

   movne  r3, #0

   moveq  r3, #1

   cmp  r2, #31

   movls  r0, #0

   andhi  r0, r3, #1

-L4:

-  cmp  r11, r1

-  bcc  L26

-  bls  L7

-  rsb  r3, r1, r11

-  cmp  ip, r3

-  bcc  L26

-  cmp  ip, #0

-  beq  L7

-  add  r10, r11, ip

-  add  lr, ip, r1

-  b  L16

-L29:

-  sub  ip, ip, #8

-  cmp  ip, #7

-  ldrd  r2, [lr, #-8]!

+  b     memcopy_default

+    

+memcopy_check_optim_overlap:

+  // r10 = dest_end, r14 = source_end

+  add  r10, r11, r12

+  add  r14, r12, r1

+

+  // Are we in the optimized case ((length >= 32) && dest_end word-aligned && source_end word-aligned)

+  cmp  r2, #31

   movls  r0, #0

-  cmp  ip, #0

-  strd  r2, [r10, #-8]!

-  beq  L7

-L16:

-  cmp  r0, #0

-  bne  L29

-  sub  r3, lr, #1

-  sub  ip, ip, #1

+  movhi  r0, #1

+  tst  r10, #0xF

+  movne  r0, #0

+  tst  r14, #0xF

+  movne  r0, #0

+  b  memcopy_overlapped

+  

+memcopy_overlapped_non_optim:

+  // We read 1 byte from the end of the source buffer

+  sub  r3, r14, #1

+  sub  r12, r12, #1

   ldrb  r3, [r3, #0]  

   sub  r2, r10, #1

-  cmp  ip, #0

+  cmp  r12, #0

+  // We write 1 byte at the end of the dest buffer

   sub  r10, r10, #1

-  sub  lr, lr, #1

+  sub  r14, r14, #1

   strb  r3, [r2, #0]

-  bne  L16

-  b   L7

-L11:

-  ldrb  r3, [lr], #1  

-  sub  ip, ip, #1

+  bne  memcopy_overlapped_non_optim

+  b   memcopy_end

+

+// r10 = dest_end, r14 = source_end

+memcopy_overlapped:

+  // Are we in the optimized case ?

+  cmp  r0, #0

+  beq  memcopy_overlapped_non_optim

+  

+  // Optimized Overlapped - Read 32 bytes

+  sub  r14, r14, #32

+  sub  r12, r12, #32

+  cmp  r12, #31

+  ldmia  r14, {r2-r9}

+  

+  // If length is less than 32 then disable optim

+  movls  r0, #0

+  

+  cmp  r12, #0

+  

+  // Optimized Overlapped - Write 32 bytes  

+  sub  r10, r10, #32

+  stmia  r10, {r2-r9}

+  

+  // while (length != 0)

+  bne  memcopy_overlapped

+  b   memcopy_end

+  

+memcopy_default_non_optim:

+  // Byte copy

+  ldrb  r3, [r14], #1  

+  sub  r12, r12, #1

   strb  r3, [r10], #1

-L26:

-  cmp  ip, #0

-  beq  L7

-L30:

+  

+memcopy_default:

+  cmp  r12, #0

+  beq  memcopy_end

+  

+// r10 = dest, r14 = source

+memcopy_default_loop:

   cmp  r0, #0

-  beq  L11

-  sub  ip, ip, #32

-  cmp  ip, #31

-  ldmia  lr!, {r2-r9}

+  beq  memcopy_default_non_optim

+  

+  // Optimized memcopy - Read 32 Bytes

+  sub  r12, r12, #32

+  cmp  r12, #31

+  ldmia  r14!, {r2-r9}

+  

+  // If length is less than 32 then disable optim

   movls  r0, #0

-  cmp  ip, #0

+  

+  cmp  r12, #0

+  

+  // Optimized memcopy - Write 32 Bytes

   stmia  r10!, {r2-r9}

-  bne  L30

-L7:

+

+  // while (length != 0)

+  bne  memcopy_default_loop

+  

+memcopy_end:

   mov  r0, r11

   ldmfd  sp!, {r4-r11, pc}

   

diff --git a/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.asm b/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.asm
index 1a5e18e12..ca8d06a55 100755
--- a/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.asm
+++ b/ArmPkg/Library/BaseMemoryLibStm/Arm/CopyMem.asm
@@ -43,70 +43,129 @@ InternalMemCopyMem (
 

 InternalMemCopyMem

   stmfd  sp!, {r4-r11, lr}
-  tst  r0, #3
+  // Save the input parameters in extra registers (r11 = destination, r14 = source, r12 = length)
   mov  r11, r0
   mov  r10, r0
-  mov  ip, r2
-  mov  lr, r1
+  mov  r12, r2
+  mov  r14, r1
+  

+memcopy_check_overlapped

+  cmp  r11, r1

+  // If (dest < source)

+  bcc  memcopy_check_optim_default

+  // If (dest <= source). But with the previous condition ->  If (dest == source)

+  bls  memcopy_end

+

+  // If (source + length < dest)

+  rsb  r3, r1, r11

+  cmp  r12, r3

+  bcc  memcopy_check_optim_default

+

+  // If (length == 0)  

+  cmp  r12, #0

+  beq  memcopy_end

+  

+  b     memcopy_check_optim_overlap

+

+memcopy_check_optim_default

+  // Check if we can use an optimized path ((length >= 32) && destination word-aligned && source word-aligned) for the memcopy (optimized path if r0 == 1)

+  tst  r0, #0xF

   movne  r0, #0
-  bne  L4
-  tst  r1, #3
+  bne   memcopy_default
+  tst  r1, #0xF
   movne  r3, #0
   moveq  r3, #1
   cmp  r2, #31
   movls  r0, #0
   andhi  r0, r3, #1
-L4
-  cmp  r11, r1
-  bcc  L26
-  bls  L7
-  rsb  r3, r1, r11
-  cmp  ip, r3
-  bcc  L26
-  cmp  ip, #0
-  beq  L7
-  add  r10, r11, ip
-  add  lr, ip, r1
-  b  L16
-L29
-  sub  ip, ip, #8
-  cmp  ip, #7
-  ldrd  r2, [lr, #-8]!
+  b     memcopy_default
+    
+memcopy_check_optim_overlap
+  // r10 = dest_end, r14 = source_end
+  add  r10, r11, r12
+  add  r14, r12, r1
+
+  // Are we in the optimized case ((length >= 32) && dest_end word-aligned && source_end word-aligned)
+  cmp  r2, #31
   movls  r0, #0
-  cmp  ip, #0
-  strd  r2, [r10, #-8]!
-  beq  L7
-L16
-  cmp  r0, #0
-  bne  L29
-  sub  r3, lr, #1
-  sub  ip, ip, #1
+  movhi  r0, #1
+  tst  r10, #0xF
+  movne  r0, #0
+  tst  r14, #0xF
+  movne  r0, #0
+  b  memcopy_overlapped

+  
+memcopy_overlapped_non_optim

+  // We read 1 byte from the end of the source buffer

+  sub  r3, r14, #1
+  sub  r12, r12, #1
   ldrb  r3, [r3, #0]  
   sub  r2, r10, #1
-  cmp  ip, #0
+  cmp  r12, #0
+  // We write 1 byte at the end of the dest buffer

   sub  r10, r10, #1
-  sub  lr, lr, #1
+  sub  r14, r14, #1
   strb  r3, [r2, #0]
-  bne  L16
-  b   L7
-L11
-  ldrb  r3, [lr], #1  
-  sub  ip, ip, #1
+  bne  memcopy_overlapped_non_optim

+  b   memcopy_end

+

+// r10 = dest_end, r14 = source_end

+memcopy_overlapped

+  // Are we in the optimized case ?

+  cmp  r0, #0

+  beq  memcopy_overlapped_non_optim

+  
+  // Optimized Overlapped - Read 32 bytes

+  sub  r14, r14, #32

+  sub  r12, r12, #32

+  cmp  r12, #31

+  ldmia  r14, {r2-r9}

+  
+  // If length is less than 32 then disable optim

+  movls  r0, #0

+  
+  cmp  r12, #0

+  

+  // Optimized Overlapped - Write 32 bytes  

+  sub  r10, r10, #32

+  stmia  r10, {r2-r9}

+  

+  // while (length != 0)

+  bne  memcopy_overlapped

+  b   memcopy_end

+  

+memcopy_default_non_optim

+  // Byte copy

+  ldrb  r3, [r14], #1  
+  sub  r12, r12, #1
   strb  r3, [r10], #1
-L26
-  cmp  ip, #0
-  beq  L7
-L30
+  
+memcopy_default

+  cmp  r12, #0
+  beq  memcopy_end
+  
+// r10 = dest, r14 = source

+memcopy_default_loop

   cmp  r0, #0
-  beq  L11
-  sub  ip, ip, #32
-  cmp  ip, #31
-  ldmia  lr!, {r2-r9}
+  beq  memcopy_default_non_optim

+  
+  // Optimized memcopy - Read 32 Bytes

+  sub  r12, r12, #32
+  cmp  r12, #31
+  ldmia  r14!, {r2-r9}
+  

+  // If length is less than 32 then disable optim

   movls  r0, #0
-  cmp  ip, #0
+  

+  cmp  r12, #0
+  

+  // Optimized memcopy - Write 32 Bytes

   stmia  r10!, {r2-r9}
-  bne  L30
-L7
+
+  // while (length != 0)

+  bne  memcopy_default_loop

+  
+memcopy_end

   mov  r0, r11
   ldmfd  sp!, {r4-r11, pc}