On pure Pascal code, “Error: Asm: ESP/RSP cannot be used as index register” or “Error: Asm: Invalid effective address”.

Attempting to compile this code for i386/win32 or x86-64/win64 with -O2 or greater:

procedure DoSomething(index, cellSize: SizeUint);
var
	buf: array[0 .. 127] of byte;
begin
	(pByte(buf) + index * cellSize)^ := 5;
end;

begin
end.

Results in Error: Asm: Invalid effective address or Error: Asm: ESP/RSP cannot be used as index register, respectively.