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* the "external alignment" (i.e., that of their starting addresses) of

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record variables is now independent of their packrecords setting
    (except for packrecords C, which already calculated a reasonable
    alignment). This means that e.g. a packed record consisting of two
    pointers will be aligned at sizeof(pointer) normally. The internal
    alignment of the individual fields of packed records obviously did
    not change, also not if those fields are records themselves.
  * The size of records without any packing atributes is also padded to
    become a multiple of this improved alignment calculation, which
    means that the size of such records may change after this patch.
    Always explicitly specify a packing for records which are used for
    data storage/transmission if you want to have a consistent layout.

git-svn-id: trunk@8409 -
This commit is contained in:
Jonas Maebe 2007-09-08 18:13:28 +00:00
parent 70d94ade58
commit 0567329343
3 changed files with 97 additions and 42 deletions
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13
compiler/ncgutil.pas
View File

@ -2191,6 +2191,9 @@ implementation
storefilepos:=current_filepos;
current_filepos:=sym.fileinfo;
l:=sym.getsize;
varalign:=sym.vardef.alignment;
if (varalign=0) then
varalign:=l;
if tf_section_threadvars in target_info.flags then
begin
if (vo_is_thread_var in sym.varoptions) then
@ -2207,11 +2210,17 @@ implementation
else
begin
if (vo_is_thread_var in sym.varoptions) then
inc(l,sizeof(aint));
begin
inc(l,sizeof(aint));
{ it doesn't help to set a higher alignment, as }
{ the first sizeof(aint) bytes field will offset }
{ everything anyway }
varalign:=sizeof(aint);
end;
list:=current_asmdata.asmlists[al_globals];
sectype:=sec_bss;
end;
varalign:=var_align(size_2_align(l));
varalign:=var_align(varalign);
maybe_new_object_file(list);
new_section(list,sectype,lower(sym.mangledname),varalign);
if (sym.owner.symtabletype=globalsymtable) or

19
compiler/pdecvar.pas
View File

@ -1437,11 +1437,20 @@ implementation
recst.padalignment:=maxpadalign;
{$endif powerpc or powerpc64}
{ Align the offset where the union symtable is added }
if (recst.usefieldalignment=C_alignment) then
usedalign:=used_align(unionsymtable.recordalignment,current_settings.alignment.recordalignmin,current_settings.alignment.maxCrecordalign)
else
usedalign:=used_align(unionsymtable.recordalignment,current_settings.alignment.recordalignmin,current_settings.alignment.recordalignmax);
case recst.usefieldalignment of
{ allow the unionsymtable to be aligned however it wants }
{ (within the global min/max limits) }
0, { default }
C_alignment:
usedalign:=used_align(unionsymtable.recordalignment,current_settings.alignment.recordalignmin,current_settings.alignment.maxCrecordalign);
{ 1 byte alignment if we are bitpacked }
bit_alignment:
usedalign:=1;
{ otherwise alignment at the packrecords alignment of the }
{ current record }
else
usedalign:=used_align(recst.fieldalignment,current_settings.alignment.recordalignmin,current_settings.alignment.recordalignmax);
end;
offset:=align(recst.datasize,usedalign);
recst.datasize:=offset+unionsymtable.datasize;

107
compiler/symtable.pas
View File

@ -79,7 +79,7 @@ interface
tabstractrecordsymtable = class(tstoredsymtable)
public
usefieldalignment, { alignment to use for fields (PACKRECORDS value), C_alignment is C style }
recordalignment, { alignment required when inserting this record }
recordalignment, { alignment desired when inserting this record }
fieldalignment, { alignment current alignment used when fields are inserted }
padalignment : shortint; { size to a multiple of which the symtable has to be rounded up }
constructor create(const n:string;usealign:shortint);
@ -760,6 +760,33 @@ implementation
end;
function field2recordalignment(fieldoffs, fieldalign: aint): aint;
begin
{ optimal alignment of the record when declaring a variable of this }
{ type is independent of the packrecords setting }
if (fieldoffs mod fieldalign) = 0 then
result:=fieldalign
else if (fieldalign >= 16) and
((fieldoffs mod 16) = 0) and
((fieldalign mod 16) = 0) then
result:=16
else if (fieldalign >= 8) and
((fieldoffs mod 8) = 0) and
((fieldalign mod 8) = 0) then
result:=8
else if (fieldalign >= 4) and
((fieldoffs mod 4) = 0) and
((fieldalign mod 4) = 0) then
result:=4
else if (fieldalign >= 2) and
((fieldoffs mod 2) = 0) and
((fieldalign mod 2) = 0) then
result:=2
else
result:=1;
end;
procedure tabstractrecordsymtable.addfield(sym:tfieldvarsym);
var
l : aint;
@ -796,6 +823,9 @@ implementation
Message(sym_e_segment_too_large);
l:=l*8;
end;
if varalign=0 then
varalign:=size_2_align(l);
recordalignment:=max(recordalignment,field2recordalignment(databitsize mod 8,varalign));
{ bit packed records are limited to high(aint) bits }
{ instead of bytes to avoid double precision }
{ arithmetic in offset calculations }
@ -823,27 +853,26 @@ implementation
if varalign=0 then
varalign:=l;
if (fieldalignment<current_settings.alignment.maxCrecordalign) then
begin
if (varalign>16) and (fieldalignment<32) then
fieldalignment:=32
else if (varalign>12) and (fieldalignment<16) then
fieldalignment:=16
{ 12 is needed for long double }
else if (varalign>8) and (fieldalignment<12) then
fieldalignment:=12
else if (varalign>4) and (fieldalignment<8) then
fieldalignment:=8
else if (varalign>2) and (fieldalignment<4) then
fieldalignment:=4
else if (varalign>1) and (fieldalignment<2) then
fieldalignment:=2;
end;
begin
if (varalign>16) and (fieldalignment<32) then
fieldalignment:=32
else if (varalign>12) and (fieldalignment<16) then
fieldalignment:=16
{ 12 is needed for long double }
else if (varalign>8) and (fieldalignment<12) then
fieldalignment:=12
else if (varalign>4) and (fieldalignment<8) then
fieldalignment:=8
else if (varalign>2) and (fieldalignment<4) then
fieldalignment:=4
else if (varalign>1) and (fieldalignment<2) then
fieldalignment:=2;
end;
fieldalignment:=min(fieldalignment,current_settings.alignment.maxCrecordalign);
end;
if varalign=0 then
varalign:=size_2_align(l);
if (usefieldalignment<> bit_alignment) then
varalignfield:=used_align(varalign,current_settings.alignment.recordalignmin,fieldalignment);
varalignfield:=used_align(varalign,current_settings.alignment.recordalignmin,fieldalignment);
sym.fieldoffset:=align(_datasize,varalignfield);
if l>high(aint)-sym.fieldoffset then
@ -857,13 +886,7 @@ implementation
if (usefieldalignment=C_alignment) then
varalignrecord:=used_align(varalign,current_settings.alignment.recordalignmin,current_settings.alignment.maxCrecordalign)
else
if (usefieldalignment=0) then
varalignrecord:=used_align(varalign,current_settings.alignment.recordalignmin,current_settings.alignment.recordalignmax)
else
begin
{ packrecords is set explicitly, ignore recordalignmax limit }
varalignrecord:=used_align(varalign,current_settings.alignment.recordalignmin,usefieldalignment);
end;
varalignrecord:=field2recordalignment(sym.fieldoffset,varalign);
recordalignment:=max(recordalignment,varalignrecord);
end;
@ -882,10 +905,19 @@ implementation
use the fieldalignment, because that is updated with the
used alignment. }
if (padalignment = 1) then
if usefieldalignment=C_alignment then
padalignment:=fieldalignment
else
padalignment:=recordalignment;
case usefieldalignment of
C_alignment:
padalignment:=fieldalignment;
{ bitpacked }
bit_alignment:
padalignment:=1;
{ default/no packrecords specified }
0:
padalignment:=recordalignment
{ specific packrecords setting -> use as upper limit }
else
padalignment:=min(recordalignment,usefieldalignment);
end;
_datasize:=align(_datasize,padalignment);
end;
@ -961,6 +993,9 @@ implementation
{ add to this record symtable }
// unionst.SymList.List.List^[i].Data:=nil;
sym.ChangeOwner(self);
varalign:=tfieldvarsym(sym).vardef.alignment;
if varalign=0 then
varalign:=size_2_align(tfieldvarsym(sym).getsize);
{ retrieve size }
if (usefieldalignment=bit_alignment) then
begin
@ -988,6 +1023,7 @@ implementation
_datasize:=(databitsize+7) div 8;
end;
tfieldvarsym(sym).fieldoffset:=databitsize;
varalignrecord:=field2recordalignment(tfieldvarsym(sym).fieldoffset div 8,varalign);
end
else
begin
@ -1000,14 +1036,15 @@ implementation
_datasize:=tfieldvarsym(sym).fieldoffset+offset;
{ update address }
tfieldvarsym(sym).fieldoffset:=_datasize;
{ update alignment of this record }
varalign:=tfieldvarsym(sym).vardef.alignment;
if varalign=0 then
varalign:=size_2_align(tfieldvarsym(sym).getsize);
varalignrecord:=used_align(varalign,current_settings.alignment.recordalignmin,fieldalignment);
recordalignment:=max(recordalignment,varalignrecord);
varalignrecord:=field2recordalignment(tfieldvarsym(sym).fieldoffset,varalign);
end;
{ update alignment of this record }
if (usefieldalignment<>C_alignment) then
recordalignment:=max(recordalignment,varalignrecord);
end;
{ update alignment for C records }
if (usefieldalignment=C_alignment) then
recordalignment:=max(recordalignment,unionst.recordalignment);
{ Register defs in the new record symtable }
for i:=0 to unionst.DefList.Count-1 do
begin