-OoDEADSTORE takes on too much.

I said that “-OoDEADSTORE breaks almost every piece of my code”, and you asked for examples.

This code compiled with -O4 -OoDEADSTORE cuts out the srcp := pInt32(src); operation, with all the consequences.

var
	src: array[0 .. 9] of int32;
	srcp: pInt32;

begin
	srcp := pInt32(src);
	srcp[0] := 1;
end.

(Sometimes a platform-specific push to the falling can be added for more obvious effect, like calling

function ClobberAX: int32; noinline; begin result := 5; end;

first on i386/win32.)