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* use BsrDWord in software mod/div

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* use a for loop instead of an until loop so code generation is potentially better

git-svn-id: trunk@22318 -
This commit is contained in:
florian 2012-09-04 18:58:20 +00:00
parent 5facc6ad5e
commit bc47125943
1 changed files with 35 additions and 47 deletions
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82
rtl/inc/generic.inc
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@ -1360,22 +1360,6 @@ end;
****************************************************************************}
{$ifdef FPC_INCLUDE_SOFTWARE_MOD_DIV}
function count_leading_zeros_32bit(l : longint) : longint;
var
i : longint;
begin
for i:=0 to 31 do
begin
if (l and (longint($80000000) shr i))<>0 then
begin
result:=i;
exit;
end;
end;
result:=i;
end;
{$ifndef FPC_SYSTEM_HAS_DIV_DWORD}
function fpc_div_dword(n,z : dword) : dword; [public,alias: 'FPC_DIV_DWORD']; compilerproc;
var
@ -1384,24 +1368,26 @@ function fpc_div_dword(n,z : dword) : dword; [public,alias: 'FPC_DIV_DWORD']; co
result:=0;
if n=0 then
HandleErrorAddrFrameInd(200,get_pc_addr,get_frame);
lzz:=count_leading_zeros_32bit(z);
lzn:=count_leading_zeros_32bit(n);
if z=0 then
exit;
lzz:=BsrDWord(z);
lzn:=BsrDWord(n);
{ if the denominator contains less zeros
then the numerator
the d is greater than the n }
if lzn<lzz then
then d is greater than the n }
if lzn>lzz then
exit;
shift:=lzn-lzz;
shift:=lzz-lzn;
n:=n shl shift;
repeat
if z>=n then
begin
z:=z-n;
result:=result+dword(1 shl shift);
end;
dec(shift);
n:=n shr 1;
until shift<0;
for shift:=shift downto 0 do
begin
if z>=n then
begin
z:=z-n;
result:=result+dword(1 shl shift);
end;
n:=n shr 1;
end;
end;
{$endif FPC_SYSTEM_HAS_DIV_DWORD}
@ -1411,27 +1397,29 @@ function fpc_mod_dword(n,z : dword) : dword; [public,alias: 'FPC_MOD_DWORD']; co
var
shift,lzz,lzn : longint;
begin
result:=0;
if n=0 then
HandleErrorAddrFrameInd(200,get_pc_addr,get_frame);
lzz:=count_leading_zeros_32bit(z);
lzn:=count_leading_zeros_32bit(n);
{ if the denominator contains less zeros
then the numerator
the d is greater than the n }
if lzn<lzz then
result:=0;
if n=0 then
HandleErrorAddrFrameInd(200,get_pc_addr,get_frame);
if z=0 then
exit;
lzz:=BsrDWord(z);
lzn:=BsrDWord(n);
{ if the denominator contains less zeros
then the numerator
then d is greater than the n }
if lzn>lzz then
begin
result:=z;
exit;
end;
shift:=lzn-lzz;
n:=n shl shift;
repeat
if z>=n then
z:=z-n;
dec(shift);
n:=n shr 1;
until shift<0;
shift:=lzz-lzn;
n:=n shl shift;
for shift:=shift downto 0 do
begin
if z>=n then
z:=z-n;
n:=n shr 1;
end;
result:=z;
end;
{$endif FPC_SYSTEM_HAS_MOD_DWORD}