Juha Manninen (gmail) escreveu:
A new Lazarus review :
http://delphimax.wordpress.com/2010/09/13/freepascal-and-lazarus-success-or-
failure/
has this comment about Lazarus source:
---
Abundant use of the Exit() command instead of nesting code in If/then/else. It
has been proven (last time in Delphi Informant Magazine) that allowing a
method to nest itself out makes faster code. It is also easier to read and
study. Exit should of course be used (it must be used in many situations) but
prudently.
---
Does nesting really create faster code?
If i understand right what you mean by nesting, the produced code is
equal at least in my simple test. See attached.
I dont know for more complex situations
Luiz
program template;
{$Mode ObjFpc}
procedure DoIt;
begin
WriteLn('DoIt');
end;
procedure UseExit(i: Integer);
begin
if i = 0 then Exit;
DoIt;
end;
procedure DontUseExit(i: Integer);
begin
if i <> 0 then
DoIt;
end;
begin //Main
UseExit(1);
DontUseExit(1);
end..file "asmExit.pas"
.section .text
.section .text
.balign 4
.balign 4
# [asmExit.pas]
# [5] begin
.globl P$TEMPLATE_DOIT
P$TEMPLATE_DOIT:
# Temps allocated between ebp-4 and ebp+0
pushl %ebp
movl%esp,%ebp
subl$4,%esp
movl%ebx,-4(%ebp)
# [6] WriteLn('DoIt');
callfpc_get_output
movl%eax,%ebx
movl$_$PROGRAM$_L10,%ecx
movl%ebx,%edx
movl$0,%eax
callfpc_write_text_shortstr
callFPC_IOCHECK
movl%ebx,%eax
callfpc_writeln_end
callFPC_IOCHECK
# [7] end;
movl-4(%ebp),%ebx
leave
ret
.section .text
.balign 4
.balign 4
# [10] begin
.globl P$TEMPLATE_USEEXIT$LONGINT
P$TEMPLATE_USEEXIT$LONGINT:
# Temps allocated between ebp-4 and ebp-4
pushl %ebp
movl%esp,%ebp
subl$4,%esp
# Var i located at ebp-4
movl%eax,-4(%ebp)
# [11] if i = 0 then Exit;
testl %eax,%eax
je .L22
# [12] DoIt;
callP$TEMPLATE_DOIT
# [13] DoIt;
callP$TEMPLATE_DOIT
# [14] DoIt;
callP$TEMPLATE_DOIT
# [15] DoIt;
callP$TEMPLATE_DOIT
# [16] DoIt;
callP$TEMPLATE_DOIT
# [17] DoIt;
callP$TEMPLATE_DOIT
# [18] DoIt;
callP$TEMPLATE_DOIT
# [19] DoIt;
callP$TEMPLATE_DOIT
# [20] DoIt;
callP$TEMPLATE_DOIT
# [21] DoIt;
callP$TEMPLATE_DOIT
.L22:
# [22] end;
leave
ret
.section .text
.balign 4
.balign 4
# [25] begin
.globl P$TEMPLATE_DONTUSEEXIT$LONGINT
P$TEMPLATE_DONTUSEEXIT$LONGINT:
# Temps allocated between ebp-4 and ebp-4
pushl %ebp
movl%esp,%ebp
subl$4,%esp
# Var i located at ebp-4
movl%eax,-4(%ebp)
# [26] if i <> 0 then
testl %eax,%eax
je .L34
# [28] DoIt;
callP$TEMPLATE_DOIT
# [29] DoIt;
callP$TEMPLATE_DOIT
# [30] DoIt;
callP$TEMPLATE_DOIT
# [31] DoIt;
callP$TEMPLATE_DOIT
# [32] DoIt;
callP$TEMPLATE_DOIT
# [33] DoIt;
callP$TEMPLATE_DOIT
# [34] DoIt;
callP$TEMPLATE_DOIT
# [35] DoIt;
callP$TEMPLATE_DOIT
# [36] DoIt;
callP$TEMPLATE_DOIT
# [37] DoIt;
callP$TEMPLATE_DOIT
.L34:
# [39] end;
leave
ret
.section .text
.balign 4
.balign 4
# [41] begin //Main
.globl PASCALMAIN
PASCALMAIN:
.globl _main
_main:
# Temps allocated between ebp+0 and ebp+0
pushl %ebp
movl%esp,%ebp
callFPC_INITIALIZEUNITS
# [42] UseExit(1);
movl$1,%eax
callP$TEMPLATE_USEEXIT$LONGINT
# [43] DontUseExit(1);
movl$1,%eax
callP$TEMPLATE_DONTUSEEXIT$LONGINT
# [44] end.
callFPC_DO_EXIT
leave
ret
.balign 4
.section .data
.ascii "FPC 2.0.4 [2006/08/21] for i386 - Win32"
.balign 16
.balign 16
.globl THREADVARLIST_P$TEMPLATE
THREADVARLIST_P$TEMPLATE:
.long 0
.balign 4
.globl FPC_THREADVARTABLES
FPC_THREADVARTABLES:
.long 3
.long THREADVARLIST_SYSTEM
.long THREADVARLIST_OBJPAS
.long THREADVARLIST_P$TEMPLATE
.balign 4
.globl FPC_RESOURCESTRINGTABLES
FPC_RESOURCESTRINGTABLES:
.long 0
.balign 4
.globl INITFINAL
INITFINAL:
.long 2,0
.long INIT$_SYSTEM
.long FINALIZE$_SYSTEM
.long INIT$_OBJPAS
.long FINALIZE$_OBJPAS
.section .data
.balign 4
.globl __stklen
__stklen:
.long 262144
.section .data
.balign 4
.globl __heapsize
__heapsize:
.long 0
.section .data
.section .data
.balign 4
.globl _$PROGRAM$_L10
_$PROGRAM$_L10:
.ascii "\004DoIt\000"
.section .data
.section .data
.section .bss
__
