> As reported in pr57540, gcc chooses bad address mode, resulting in A)
> invariant part of address expression is not kept or hoisted; b) additional
> computation which should be encoded in address expression. The reason is
> when gcc runs into "addr+offset" (which is invalid) during expanding, it
> pre-computes the entire address and accesses memory unit using "MEM[reg]".
> Yet we can force addr into register and try to generate "reg+offset" which
> is valid for targets like ARM. By doing this, we can:
> 1) keep addr in loop invariant form and hoist it later;
> 2) saving additional computation by taking advantage of scaled addressing
> mode;
Does the invalid address not go through arm_legitimize_address from here?
/* Perform machine-dependent transformations on X
in certain cases. This is not necessary since the code
below can handle all possible cases, but machine-dependent
transformations can make better code. */
{
rtx orig_x = x;
x = targetm.addr_space.legitimize_address (x, oldx, mode, as);
if (orig_x != x && memory_address_addr_space_p (mode, x, as))
goto done;
}
--
Eric Botcazou
