Below is a test piece that shows how to "roll your own" version of FASTCALL so that you get a stack frame free procedure where you can routinely use EBP without having to perform stack corrections on stack arguments with any stack changes. You still must preserve and restore any of EBX ESI EDI and EBP if you use them but you are free from having to adjust ESP after pushes and pops.
#IF 0 ' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
With the FASTCALL procedures the arguments are passed directly in registers bypassing the
overhead of the stack. In the system used below you can pass up to 3 arguments using the
normal volatile registers EAX ECX & EDX and in these procedures they are written in the
order,
arg1 = EAX
arg2 = ECX
arg3 = EDX
If you are passing only 1 argument you will only use EAX, with 2 arguments it will be EAX & ECX
With 3 arguments you will use EAX ECX & EDX.
The MACROS are designed to make calling the procedures more convenient but they have limitations
that are different from high level code. You must pass data that can be written directly to a
32 bit register.
With procedures constructed in this manner you have access to 7 registers and do not have to
deal with the stack making corrections to stack based addresses. You must properly comply with
the Intel ABI rules for register preservation but by doing so you can use 4 extra registers.
EBX ESI EDI & EBP
If you were going to use all 4 registers you would use the following code.
push ebx
push esi
push edi
push ebp
; write your algorithm here
pop ebp
pop edi
pop esi
pop ebx
NOTE that the restores are all popped in reverse order to the pushes.
If you don't need all 4 just preserve and restore the ones you use.
If you need extra memory variables without a stack being available you can either allocated
GLOBAL or STATIC variables within the procedure.
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#include "\basic\include\win32api.inc"
' ------------------------------
' return address of BASIC string
' ------------------------------
MACRO FUNCTION sadd(quoted)
MACROTEMP bas
LOCAL bas as STRING
bas = quoted
END MACRO = StrPtr(bas)
' ------------------------------
' --------------------
' fastcall memory copy
' --------------------
MACRO fcmemcopy(psrc,pdst,bcnt)
PREFIX "!"
mov eax, psrc
mov ecx, pdst
mov edx, bcnt
call fastcall_mcopy
END PREFIX
END MACRO
' ------------------------
' fastcall simple len algo
' ------------------------
MACRO FUNCTION fcgetlen(pstr)
MACROTEMP retval
LOCAL retval as DWORD
PREFIX "!"
mov eax, psrc
call fastcall_len
mov retval, eax
END PREFIX
END MACRO = retval
' ----------------------------
' fastcall high speed len algo
' ----------------------------
MACRO FUNCTION fcstrlen(pstr)
MACROTEMP retval
LOCAL retval as DWORD
PREFIX "!"
mov eax, psrc
call fastcall_strlen
mov retval, eax
END PREFIX
END MACRO = retval
' -------------------------------
' fastcall BYTE level memory fill
' -------------------------------
MACRO fcmfillB(src,count,filler)
PREFIX "!"
mov eax, src
mov ecx, count
mov edx, filler
call memfillB
END PREFIX
END MACRO
' --------------------------------
' fastcall DWORD level memory fill
' --------------------------------
MACRO fcmfillD(src,count,filler)
PREFIX "!"
mov eax, src
mov ecx, count
mov edx, filler
call memfillD
END PREFIX
END MACRO
' ---------------------------------------------------------
' allocate GLOBAL memory and assign a string to it
' For an empty buffer use "" for the string
' ---------------------------------------------------------
MACRO FUNCTION globalstr(quoted_text,bytecount)
MACROTEMP globalstring
GLOBAL globalstring as STRING * bytecount
globalstring = quoted_text
END MACRO = VarPtr(globalstring)
' ---------------------------------------------------------
' allocate fixed memory in the executable BSS section
' ---------------------------------------------------------
MACRO FUNCTION fixedmem(bytecount)
MACROTEMP bss_section_memory
GLOBAL bss_section_memory as STRING * bytecount
END MACRO = VarPtr(bss_section_memory)
' ---------------------------------------------------------
' allocate local memory and assign a string to it
' For an empty buffer use "" for the string
' ---------------------------------------------------------
MACRO FUNCTION localstr(quoted_text,bytecount)
MACROTEMP szstring
LOCAL szstring as STRINGZ * bytecount
szstring = quoted_text
END MACRO = VarPtr(szstring)
' ---------------------------------------------------------
' allocate local memory and return its address
' ---------------------------------------------------------
MACRO FUNCTION localmem(bytecount)
MACROTEMP stack_memory
LOCAL stack_memory as STRING * bytecount
END MACRO = VarPtr(stack_memory)
' ---------------------------------------------------------
' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
FUNCTION PBmain as LONG
LOCAL psrc as STRINGZ PTR
LOCAL pdst as STRINGZ PTR
LOCAL bcnt as DWORD
psrc = localstr("This is a test",1024)
pdst = localmem(1024)
bcnt = fcstrlen(psrc)
fcmemcopy(psrc,pdst,bcnt)
StdOut @pdst
pdst = localmem(1024)
fcmfillD(pdst,128,"XXXX")
StdOut @pdst
waitkey$
End FUNCTION
' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
FASTPROC fastcall_mcopy
PREFIX "!"
push ebx ; Intel ABI compliant
push esi ; preserve registers
push edi
cld
mov esi, eax ; source address in esi
mov edi, ecx ; destination address in edi
mov ecx, edx ; byte count in ecx
mov ebx, edx ; put a copy of byte count in ebx
shr ecx, 2
rep movsd
mov ecx, ebx
and ecx, 3
rep movsb
pop edi ; restore registers
pop esi
pop ebx
ret
END PREFIX
END FASTPROC
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FASTPROC fastcall_len
PREFIX "!"
mov ecx, eax
sub eax, 1
align 4
lbl0:
add eax, 1
cmp BYTE PTR [eax], 0
jne lbl0
sub eax, ecx
ret
END PREFIX
END FASTPROC
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FASTPROC fastcall_strlen
PREFIX "!"
; -----------------------
; Agner Fog's StrLen algo
; src pointer is in EAX
; -----------------------
push esi
push edi
lea edx, [eax+3] ; pointer+3 used in the end
mov esi, &H80808080
; -----------
; unroll by 4
; -----------
lbl1:
mov edi, [eax] ; read first 4 bytes
add eax, 4 ; increment pointer
lea ecx, [edi-&H01010101] ; subtract 1 from each byte
not edi ; invert all bytes
and ecx, edi ; and these two
and ecx, esi
jnz nxt
mov edi, [eax] ; read first 4 bytes
add eax, 4 ; increment pointer
lea ecx, [edi-&H01010101] ; subtract 1 from each byte
not edi ; invert all bytes
and ecx, edi ; and these two
and ecx, esi
jnz nxt
mov edi, [eax] ; read first 4 bytes
add eax, 4 ; increment pointer
lea ecx, [edi-&H01010101] ; subtract 1 from each byte
not edi ; invert all bytes
and ecx, edi ; and these two
and ecx, esi
jnz nxt
mov edi, [eax] ; read first 4 bytes
add eax, 4 ; 4 increment DWORD pointer
lea ecx, [edi-&H01010101] ; subtract 1 from each byte
not edi ; invert all bytes
and ecx, edi ; and these two
and ecx, esi
jz lbl1 ; no zero bytes, continue loop
nxt:
test ecx, &H00008080 ; test first two bytes
jnz lbl2
shr ecx, 16 ; not in the first 2 bytes
add eax, 2
lbl2:
shl cl, 1 ; use carry flag to avoid branch
sbb eax, edx ; compute length
pop edi
pop esi
ret
END PREFIX
END FASTPROC
' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
' FUNCTION memfillB(ByVal pmem as DWORD,ByVal lmem as DWORD,ByVal fillchar as BYTE) as DWORD
FASTPROC memfillB
PREFIX "!"
push edi ; Intel ABI complaint
mov edi, eax
mov al, dl
rep stosb
pop edi ; restore EDI
ret
END PREFIX
END FASTPROC
' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
' FUNCTION memfillD(ByVal pmem as DWORD,ByVal lmem as DWORD,ByVal fillchars as DWORD) as DWORD
FASTPROC memfillD
PREFIX "!"
push esi ; Intel ABI complaint
push edi ; preserve registers
mov esi, ecx ; count stored in ESI
mov edi, eax ; address in EDI
mov eax, edx ; fill chars in eax
cld ; write forward
shr ecx, 2 ; int divide by 4
rep stosd
mov ecx, esi ; reload count
and ecx, 3 ; calculate tail length
rep stosb
pop edi ; restore registers
pop esi
ret
END PREFIX
END FASTPROC
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Steve,
that's an interesting idea. Do you have plans to post it inside the PB forum, too? I think there are some coders which are interested.
Gunther
Gunther,
I put a link in their ASM section.
Quote from: hutch-- on December 16, 2014, 09:21:38 PM
I put a link in their ASM section.
Good idea. We would need a few more active PB & ASM coders from there.
Gunther