Bug#895693: arm64: Incorrect record member value when returned from a function

[Punit Agrawal]

Source: fpc
Version: 3.0.4+dfsg-16
Severity: normal

Dear Maintainer,

While investigating build failure reported in #891682 I've stumbled
upon what seems like a free pascal compiler issue on arm64.

The value of a member of a record returned by a function varies
depending on usage.

The observed value of

   S.Width where S := R.ScaleAround0(2)

differs from the value of

   R.ScaleAround0(2).Width

The values differ on arm64 but agree on x86-64.

The attached reproducer gives the following output on arm64 -

    arm64:~/src/fpc-test$ ./test
    S.Width=0 R.ScaleAround0(2).Width=214748364800

while on x86-64

    x86-64$ ./test
    S.Width=0 R.ScaleAround0(2).Width=0
        
The reproducer is derived from a failing test in Castle Game Engine.

Thanks,
Punit

program test;

{$mode objfpc}{$H+}
{$modeSwitch advancedRecords}

type
   TRectangle = record
                   public
                   Left, Bottom: Integer;
                   Width, Height: Cardinal;

                function ScaleAround0(const Factor: Single): TRectangle;
                end;

function TRectangle.ScaleAround0(const Factor: Single): TRectangle;
begin
   if Width <= 0 then
   begin
      Result.Width  := Width;
      Result.Left   := Left;
   end else
      Writeln('This should never happen');

   Result.Height := Height;
   Result.Bottom := Bottom;
end;

function Rectangle(const Left, Bottom: Integer;
                   const Width, Height: Cardinal): TRectangle;
begin
   Rectangle.Left := Left;
   Rectangle.Bottom := Bottom;
   Rectangle.Width := Width;
   Rectangle.Height := Height;
end;

var
   R, S :  TRectangle;
begin
   R := Rectangle(10, 20, 0, 50);
   S := R.ScaleAround0(2);

   Writeln('S.Width=', S.Width, ' R.ScaleAround0(2).Width=', 
R.ScaleAround0(2).Width);   
end.