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> Compiler Internals > Some cleanup sugestions on Fasm code |
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vid 01 Aug 2005, 07:16
don't forget that this (uncommented) code shuld be as explainative as possible, and "lods" clearly means skipping character, unlike "inc".
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01 Aug 2005, 07:16 |
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MCD 01 Aug 2005, 13:39
Well, actually I have discovered hundreds of such repeating paterns in Fasm code, but there isn't enough space to descibe them all here. But imagine what happens when you upgrade to a new version of Fasm but with all those code fixes you nade are lost? So better don't do such changes until you told Tomasz
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01 Aug 2005, 13:39 |
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El Tangas 01 Aug 2005, 16:29
I did change my fasm copy, just for testing, but this are just sugestions, I don't really mind if they are not implemented. This is just the way I would code if I was the author of Fasm. It's just that lods takes 5 cycles in 386 and uses memory bandwidth, while inc takes 2 cycles.
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01 Aug 2005, 16:29 |
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Tomasz Grysztar 01 Aug 2005, 16:51
Well, actually I feel ashamed I have left so many of such relicts - they are direct result of re-editing the same code pieces hundreds of times. From time to time, when I review some larger parts of code, I fix all such things - for example I have removed a lot of more or less similar ones from the X86.INC when I was upgrading it to X86_64.INC, I did review almost all the code there that time; but the PARSER.INC and EXPRESSI.INC were not generally revised for a very long time - perhaps that's why you've found such things there in the first place.
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01 Aug 2005, 16:51 |
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El Tangas 01 Aug 2005, 19:48
Nothing to be ashamed of
Fasm is a great piece of code, but its complexity is increasing, and this kind of leftovers will tend to accumulate... Well, I do have a few more things to report (expressi.inc): Code:
dec esi
mov al,[esi+1]
to
mov al,[esi]
dec esi
motive: saves one byte... Code:
shld edx,eax,1
shl eax,1
and
shl eax,1
rcl edx,1
to
add eax,eax
adc edx,edx
In general:
shl reg,1 -> add reg,reg
rcl reg,1 -> adc reg,reg
motive: faster. And finally, in preproce.inc: Code:
convert_line_data:
cmp edi,[memory_end]
jae out_of_memory
lods byte [esi]
cmp al,20h
je convert_line_data
cmp al,9
je convert_line_data
-> dec esi
-> lods byte [esi]
mov ah,al
the marked lines are not needed. |
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01 Aug 2005, 19:48 |
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Tomasz Grysztar 01 Aug 2005, 19:55
Thanks!
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01 Aug 2005, 19:55 |
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