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* fixed overflow checking in qword multiplication

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This commit is contained in:
florian 2004-09-26 08:52:51 +00:00
parent f77e8ab5a6
commit 9205c6e800
1 changed files with 64 additions and 10 deletions
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74
rtl/i386/int64p.inc
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@ -168,17 +168,19 @@
the longbool for checkoverflow avoids a misaligned stack
}
function fpc_mul_qword(f1,f2 : qword;checkoverflow : longbool) : qword;[public,alias: 'FPC_MUL_QWORD']; {$ifdef hascompilerproc} compilerproc; {$endif}
var
_f1 : qword;
r : qword;
r : qword;
overflowed : boolean;
begin
_f1:=f1;
overflowed:=false;
{ the following piece of code is taken from the
AMD Athlon Processor x86 Code Optimization manual }
asm
movl f1+4,%edx
movl f2+4,%ecx
cmpl $0,checkoverflow
jnz .Loverflowchecked
orl %ecx,%edx
movl f2,%edx
movl f1,%eax
@ -194,18 +196,70 @@
.Lqwordmulready:
movl %eax,r
movl %edx,r+4
end [ 'eax','edx','ecx' ];
jmp .Lend
.Loverflowchecked:
{ if both upper dwords are <>0 then it overflows always }
or %ecx,%ecx
jz .Loverok1
or %edx,%edx
jnz .Loverflowed
.Loverok1:
{ overflow checked code }
orl %ecx,%edx
movl f2,%edi
movl f1,%esi
jnz .Lqwordmultwomul2
movl %edi,%eax
mull %esi
movl %eax,%esi
movl %edx,%edi
jmp .Lqwordmulready2
.Lqwordmultwomul2:
movl f1+4,%eax
mull %edi
movl %eax,%edi
jc .Loverflowed
movl %esi,%eax
mull %ecx
movl %eax,%ecx
jc .Loverflowed
addl %edi,%ecx
jc .Loverflowed
movl f2,%eax
mull %esi
movl %eax,%esi
movl %edx,%edi
addl %ecx,%edi
jc .Loverflowed
.Lqwordmulready2:
movl %esi,r
movl %edi,r+4
jmp .Lend
.Loverflowed:
movb $1,overflowed
.Lend:
end [ 'eax','edx','ecx','edi','esi' ];
fpc_mul_qword:=r;
{ if one of the operands is greater than the result an
overflow occurs }
if checkoverflow and (_f1<>0) and (f2<>0) and
((_f1>fpc_mul_qword) or (f2>fpc_mul_qword)) then
if overflowed then
HandleErrorFrame(215,get_frame);
end;
{
$Log$
Revision 1.4 2004-07-25 11:50:39 florian
Revision 1.5 2004-09-26 08:52:51 florian
* fixed overflow checking in qword multiplication
Revision 1.4 2004/07/25 11:50:39 florian
* assembler version of mod_qword_word reactivated
Revision 1.3 2004/05/10 20:58:20 florian