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* patch by Rika: another improvement of cutils.newalignment, part of #39496

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florian 2021-12-25 19:37:27 +01:00
parent c0979bbc0c
commit abc4a0a4e6
1 changed files with 7 additions and 5 deletions
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compiler/cutils.pas
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@ -295,11 +295,13 @@ implementation
function newalignment(oldalignment: longint; offset: int64): longint; function newalignment(oldalignment: longint; offset: int64): longint;
begin begin
{ oldalignment must be power of two. { oldalignment must be power of two.
Works even for negative offsets (but not alignments),
as two's complement of, say, 2^4+2^3 is 11000 and -2^4-2^3 is 11...1101000 - Negating two's complement number keeps its tail '100...000' and complements all bits above.
both end with exactly N zeros, where N is the largest power of two that divides the number "x and -x" extracts this tail of 'x'.
(smallest power of two involved in these sums). } Said tail of "oldalignment or offset" is the desired answer. }
result:=1 shl BsfQWord(qword(offset or oldalignment));
result:=oldalignment or longint(offset); { high part of offset won't matter as long as alignment is 32-bit }
result:=result and -result;
end; end;