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+ (safe) heuristics to use DW_CFA_advance_loc1 in CFI

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git-svn-id: trunk@48687 -
This commit is contained in:
florian 2021-02-16 21:16:54 +00:00
parent 436a0d3f9e
commit 5b29e7a3ec
1 changed files with 30 additions and 1 deletions
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31
compiler/cfidwarf.pas
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@ -543,6 +543,8 @@ implementation
var
currloclabel : tasmlabel;
hp : tai;
instrcount : longint;
dwarfloc: Integer;
begin
if FLastloclabel=nil then
internalerror(200404082);
@ -562,9 +564,36 @@ implementation
break;
hp:=tai(hp.Previous);
end;
{ check if the last advance entry is less then 8 instructions away:
as x86 instructions might not be bigger than 15 bytes and most other
CPUs use only 4 byte instructions or smaller, this is safe
we could search even more but this takes more time and 8 instructions should be normally enough
}
hp:=tai(list.Last);
instrcount:=0;
dwarfloc:=DW_CFA_advance_loc4;
while assigned(hp) and (instrcount<8) do
begin
{ stop if we find any tai which results in code or data }
if not(hp.typ in ([ait_label,ait_instruction]+SkipInstr)) then
break;
if (hp.typ=ait_label) and (tai_label(hp).labsym=FLastloclabel) then
begin
dwarfloc:=DW_CFA_advance_loc1;
break;
end;
if hp.typ=ait_instruction then
inc(instrcount);
hp:=tai(hp.Previous);
end;
current_asmdata.getlabel(currloclabel,alt_dbgframe);
list.concat(tai_label.create(currloclabel));
DwarfList.concat(tdwarfitem.create_reloffset(DW_CFA_advance_loc4,doe_32bit,FLastloclabel,currloclabel));
if dwarfloc=DW_CFA_advance_loc1 then
DwarfList.concat(tdwarfitem.create_reloffset(DW_CFA_advance_loc1,doe_8bit,FLastloclabel,currloclabel))
else
DwarfList.concat(tdwarfitem.create_reloffset(DW_CFA_advance_loc4,doe_32bit,FLastloclabel,currloclabel));
FLastloclabel:=currloclabel;
end;