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FPC compiles pusha/popa as a pushaw/popaw. Is it doing right?
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Topic: FPC compiles pusha/popa as a pushaw/popaw. Is it doing right? (Read 995 times)
Avinash
Full Member
Posts: 118
FPC compiles pusha/popa as a pushaw/popaw. Is it doing right?
«
on:
June 05, 2021, 01:11:24 pm »
I would expect PUSHAD/POPAD from 32-bit compiler.
Logged
marcov
Administrator
Hero Member
Posts: 11452
FPC developer.
Re: FPC compiles pusha/popa as a pushaw/popaw. Is it doing right?
«
Reply #1 on:
June 05, 2021, 02:34:52 pm »
They have the same opcode, so the meaning is probably set by the mode ? That might be the disassembler at fault. (or whatever the backend assembler accepts, in the case of -a)
Logged
Avinash
Full Member
Posts: 118
Re: FPC compiles pusha/popa as a pushaw/popaw. Is it doing right?
«
Reply #2 on:
June 05, 2021, 03:51:48 pm »
Code: Pascal
[Select]
[+]
[-]
{$mode objfpc}
{$asmmode intel}
var
L
:
LongInt
;
begin
asm
xor
eax
,
eax
//pusha
dec eax
//popa
mov L
,
eax
end
;
WriteLn
(
HexStr
(
L
,
8
)
)
;
end
.
FFFFFFFF
Code: Pascal
[Select]
[+]
[-]
{$mode objfpc}
{$asmmode intel}
var
L
:
LongInt
;
begin
asm
xor
eax
,
eax
pusha
dec eax
popa
mov L
,
eax
end
;
WriteLn
(
HexStr
(
L
,
8
)
)
;
end
.
FFFF0000
Logged
PascalDragon
Hero Member
Posts: 5481
Compiler Developer
Re: FPC compiles pusha/popa as a pushaw/popaw. Is it doing right?
«
Reply #3 on:
June 05, 2021, 04:56:08 pm »
Yes, this is by design. See this comment from the compiler's source:
Code: Pascal
[Select]
[+]
[-]
{ pushf/popf/pusha/popa have to default to 16 bit in Intel mode
(Intel manual and Delphi-compatbile) -- setting the opsize for
these instructions doesn't change anything in the internal assember,
so change the opcode }
Logged
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FPC compiles pusha/popa as a pushaw/popaw. Is it doing right?
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