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From: Mirsad Todorovac
Subject: GPC preformance kludge with local initialized arrays
Date: 7 Jun 2003, 19:57:29
Note the following lsiting, and resulting assembly code (i686, Linux):
You might think that the function is very optimized, since it requires
only two comparisons and a lookup in table per character checked?
Alas, GPC does a proper call to the real memcpy() function of complete
``v'' array on each call of function DigitValue() !!!
This makes the run twice as slow as when ``v'' array is made global
(edited):
-----------------------------------------------------
make test arr a=8
116.290u 0.400s 1:59.62 97.5% 0+0k 0+0io 10385pf+0w
time a.out arr a=8
114.190u 0.280s 1:58.53 96.5% 0+0k 0+0io 120pf+0w
114.500u 0.210s 2:03.95 92.5% 0+0k 0+0io 120pf+0w
114.650u 0.040s 1:57.13 97.9% 0+0k 0+0io 121pf+0w
114.840u 0.020s 1:57.00 98.1% 0+0k 0+0io 120pf+0w
115.180u 0.040s 2:05.03 92.1% 0+0k 0+0io 120pf+0w
106.200u 1.390s 2:07.25 84.5% 0+0k 0+0io 120pf+0w
111.700u 0.080s 2:04.02 90.1% 0+0k 0+0io 120pf+0w
make test arr a=8 glob
65.840u 0.160s 1:07.62 97.6% 0+0k 0+0io 10385pf+0w
time a.out arr a=8 glob
63.610u 0.060s 1:06.63 95.5% 0+0k 0+0io 120pf+0w
63.710u 0.030s 1:05.21 97.7% 0+0k 0+0io 120pf+0w
63.620u 0.040s 1:06.02 96.4% 0+0k 0+0io 120pf+0w
63.610u 0.030s 1:05.41 97.2% 0+0k 0+0io 120pf+0w
63.840u 0.000s 1:05.15 97.9% 0+0k 0+0io 120pf+0w
63.980u 0.010s 1:05.29 98.0% 0+0k 0+0io 120pf+0w
64.000u 0.020s 1:05.19 98.2% 0+0k 0+0io 120pf+0w
-----------------------------------------------------
Just FYI, making ``v'' array [0..255] of Integer (for aligned access) made
it even 10s slower (probably problems with FSB and cache), instead of what
is commonly said, and complete code is not a bit faster from this variant:
function DigitValue (Dig: Char): Integer; attribute (inline, const);
var d : Integer; attribute (register);
begin
if (Dig >= '0') and (Dig <= '9' ) then
DigitValue := Ord (Dig) - Ord ('0')
else if (Dig >= 'a') and (Dig <= 'z') then
DigitValue := Ord (Dig) - Ord ('a') + 10
else if (Dig >= 'A') and (Dig <= 'Z') then
DigitValue := Ord (Dig) - Ord ('A') + 10
else
DigitValue := -1
end;
... even though this code has six branches.
Is it the GNU Pascal problem or the back-end problem?
NOTE: even attribute (const) after initialization of the array didn't help
to evade memcpy().
Mirsad
isvalidnumberbase.pas:
----------------------------------------------------------------------------
program isvalidnum (output);
var i, Base: Integer;
OK : Boolean;
function IsValidNumberBase2 (s: String; Base: Integer): Boolean; attribute(const);
var i, dv : Integer; attribute (register);
b : Byte; attribute (register);
function DigitValue (Dig: Char): Integer; {attribute (inline, const);}
var d : Integer; attribute (register);
{$if 0}
{$if Low (Char) < 0}
{$error "this won't work: negative Char used as index}
{$endif}
{$endif}
v : array [0..255] of ByteInt = (
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, -1, -1, -1, -1,
-1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 );
begin
if (Dig >= '0') and (Dig <= 'z') then
DigitValue := v[Ord (Dig)]
else
DigitValue := -1;
end;
begin
b := Base;
Assert ((b >= 2) and (b <= 36), 'base out of range (2..36)');
i := 1;
if s[i] = '-' then
Inc (i);
for i := i to Length (s) do
{$define VERSION1}
{$ifdef VERSION1}
begin
dv := DigitValue (s[i]);
if (dv < 0) or (dv >= b) then
Return False
end;
{$else}
if not (DigitValue (s[i]) in [0 .. b-1]) then
Return False;
{$endif}
Return True;
end;
begin { main }
OK := IsValidNumberBase2 ('010101010101101010101', 2) and
not IsValidNumberBase2 ('0101010210101101010101', 2) and
IsValidNumberBase2 ('0121012210101101010101', 3);
if OK then
WriteLn ('OK');
end.
-------------------------------------------------------------------------
isvalidnumberbase.s (edited):
-------------------------------------------------------------------------
.file "isvalidnumberbase.pas"
.local I
.comm I,4,4
.local Base
.comm Base,4,4
.local Ok
.comm Ok,1,1
.section .rodata
.LC0:
.byte -1
.
.
.
.byte -1
.byte -1
.byte -1
.byte 0
.byte 1
.byte 2
.byte 3
.byte 4
.byte 5
.byte 6
.byte 7
.byte 8
.byte 9
.byte -1
.byte -1
.byte -1
.byte -1
.byte -1
.byte -1
.byte -1
.byte 10
.byte 11
.byte 12
.byte 13
.byte 14
.byte 15
.byte 16
.byte 17
.byte 18
.byte 19
.byte 20
.byte 21
.byte 22
.byte 23
.byte 24
.byte 25
.byte 26
.byte 27
.byte 28
.byte 29
.byte 30
.byte 31
.byte 32
.byte 33
.byte 34
.byte 35
.byte 36
.byte -1
.byte -1
.byte -1
.byte -1
.byte -1
.byte 10
.byte 11
.byte 12
.byte 13
.byte 14
.byte 15
.byte 16
.byte 17
.byte 18
.byte 19
.byte 20
.byte 21
.byte 22
.byte 23
.byte 24
.byte 25
.byte 26
.byte 27
.byte 28
.byte 29
.byte 30
.byte 31
.byte 32
.byte 33
.byte 34
.byte 35
.byte 36
.byte -1
.byte -1
.
.
.
.byte -1
.byte -1
.byte -1
.byte -1
.text
.p2align 4,,15
.type Digitvalue.0,@function
Digitvalue.0:
pushl %ebp
movl %esp, %ebp
subl $296, %esp
movl %ebx, -4(%ebp)
leal -280(%ebp), %eax
movzbl 8(%ebp), %ebx
movl %ecx, -12(%ebp)
movl $256, 8(%esp)
movl $.LC0, 4(%esp)
movl %eax, (%esp)
call memcpy
cmpb $47, %bl
jbe .L4
cmpb $122, %bl
ja .L4
movzbl %bl, %eax
movsbl -280(%eax,%ebp),%eax
.L5:
movl -4(%ebp), %ebx
movl %ebp, %esp
popl %ebp
ret
.p2align 4,,7
.L4:
movl $-1, %eax
jmp .L5
.Lfe1:
.size Digitvalue.0,.Lfe1-Digitvalue.0
.section .rodata.str1.1,"aMS",@progbits,1
.LC1:
.string "base out of range (2..36)"
.text
.p2align 4,,15
.globl Isvalidnumberbase2
.type Isvalidnumberbase2,@function
Isvalidnumberbase2:
pushl %ebp
movl %esp, %ebp
pushl %edi
pushl %esi
pushl %ebx
subl $92, %esp
movl 8(%ebp), %edi
movzbl 12(%ebp), %eax
cmpb $1, %al
seta %bl
movb %al, -73(%ebp)
testb %bl, %bl
je .L6
cmpb $36, %al
setbe %bl
.L6:
movl $25, -72(%ebp)
leal -64(%ebp), %eax
movl $25, 8(%esp)
movl $.LC1, 4(%esp)
movl %eax, (%esp)
call memcpy
leal -72(%ebp), %eax
movl %eax, 4(%esp)
movzbl %bl, %eax
movl $1, %ebx
movl $25, -68(%ebp)
movl %eax, (%esp)
call _p_Assert
cmpb $45, 8(%edi)
je .L18
.L8:
movl 4(%edi), %esi
cmpl %esi, %ebx
jg .L9
movb $0, -74(%ebp)
.p2align 4,,15
.L10:
cmpb $0, -74(%ebp)
je .L12
cmpl %esi, %ebx
je .L9
incl %ebx
.L12:
movb $1, -74(%ebp)
leal -24(%ebp), %ecx
movzbl 7(%edi,%ebx), %eax
movl %eax, (%esp)
call Digitvalue.0
movl %eax, %ecx
shrl $31, %ecx
testb %cl, %cl
movl %eax, %edx
jne .L17
movzbl -73(%ebp), %eax
cmpl %eax, %edx
jl .L14
testl %edx, %edx
js .L14
movb $1, %cl
.L14:
testb %cl, %cl
je .L10
.L17:
xorl %eax, %eax
.L1:
addl $92, %esp
popl %ebx
popl %esi
popl %edi
popl %ebp
ret
.p2align 4,,7
.L9:
movb $1, %al
jmp .L1
.L18:
movl $2, %ebx
jmp .L8
.Lfe2:
.size Isvalidnumberbase2,.Lfe2-Isvalidnumberbase2
.section .rodata.str1.1
.LC2:
.string "010101010101101010101"
.LC5:
.string "OK"
.LC4:
.string "0121012210101101010101"
.LC3:
.string "0101010210101101010101"
.text
.p2align 4,,15
.globl pascal_main_program
.type pascal_main_program,@function
pascal_main_program:
pushl %ebp
movl %esp, %ebp
subl $136, %esp
movl $21, 8(%esp)
leal -32(%ebp), %eax
movl $21, -40(%ebp)
movl $.LC2, 4(%esp)
movl %eax, (%esp)
call memcpy
leal -40(%ebp), %eax
movl $21, -36(%ebp)
movl $2, 4(%esp)
movl %eax, (%esp)
call Isvalidnumberbase2
testb %al, %al
jne .L28
.L21:
testb %al, %al
jne .L29
.L23:
movb %al, Ok
testb %al, %al
jne .L30
.L19:
movl %ebp, %esp
popl %ebp
ret
.p2align 4,,7
.L30:
movl $22, 24(%esp)
movl $2, 20(%esp)
movl $.LC5, 16(%esp)
movl $17, 12(%esp)
movl $2, 8(%esp)
movl $784, 4(%esp)
movl $_p_Output, (%esp)
call _p_Internal_Write
movl _p_InOutRes, %eax
testl %eax, %eax
je .L19
jmp .L31
.p2align 4,,7
.L29:
movl $22, -104(%ebp)
leal -96(%ebp), %eax
movl $22, 8(%esp)
movl $.LC4, 4(%esp)
movl %eax, (%esp)
call memcpy
leal -104(%ebp), %eax
movl $22, -100(%ebp)
movl $3, 4(%esp)
movl %eax, (%esp)
call Isvalidnumberbase2
jmp .L23
.p2align 4,,7
.L28:
movl $22, -72(%ebp)
leal -64(%ebp), %eax
movl $22, 8(%esp)
movl $.LC3, 4(%esp)
movl %eax, (%esp)
call memcpy
leal -72(%ebp), %eax
movl $22, -68(%ebp)
movl $2, 4(%esp)
movl %eax, (%esp)
call Isvalidnumberbase2
testb %al, %al
sete %al
jmp .L21
.L31:
call _p_CheckInOutRes
.Lfe3:
.size pascal_main_program,.Lfe3-pascal_main_program
.data
.type ctor_run_condition_14.1,@object
.size ctor_run_condition_14.1,1
ctor_run_condition_14.1:
.byte 0
.text
.p2align 4,,15
.globl init_pascal_main_program
.type init_pascal_main_program,@function
init_pascal_main_program:
cmpb $0, ctor_run_condition_14.1
pushl %ebp
movl %esp, %ebp
je .L34
popl %ebp
ret
.p2align 4,,7
.L34:
popl %ebp
movb $1, ctor_run_condition_14.1
jmp _p_DoInitProc
.Lfe4:
.size init_pascal_main_program,.Lfe4-init_pascal_main_program
.p2align 4,,15
.globl main
.type main,@function
main:
pushl %ebp
movl %esp, %ebp
subl $24, %esp
movl __GPC_RTS_VERSION_20030507__, %eax
movl 16(%ebp), %eax
andl $-16, %esp
movl %eax, 8(%esp)
movl 12(%ebp), %eax
movl %eax, 4(%esp)
movl 8(%ebp), %eax
movl %eax, (%esp)
call _p_initialize
call init_pascal_main_program
call pascal_main_program
call _p_finalize
movl %ebp, %esp
xorl %eax, %eax
popl %ebp
ret
.Lfe5:
.size main,.Lfe5-main
.ident "GCC: (GNU) 3.2.1"
-------------------------------------------------------------------------------
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