> >> Did you see the failures even after your mips_regno_mode_ok_for_base_p
> >> change? LRA should know how to reload a "W" address.
> >
> > Yes but I realize there is more. It fails because $sp is now included
> > in BASE_REG_CLASS and "W" is based on it. However, I suppose that
> > it would be too eager to say it is wrong and likely there is something
> > missing
> > in LRA if we want to keep all alternatives. Currently there is no check
> > if a reloaded operand has a valid address, use of $sp in lbu/lhu cases.
> > Even if we added extra checks we are less likely to benefit as we need
> > to reload the base into register.
>
> Not sure what you mean, sorry. "W" exists specifically to exclude
> $sp-based and $pc-based addresses. LRA AFAIK should already be able
> to reload addresses that are valid in the TARGET_LEGITIMATE_ADDRESS_P
> sense but which do not match the constraints for a particular insn.
>
> Can you remember one of the tests that fails?
I couldn't trigger the problem with the original testcase but found another
one that reveals it. The following needs to compiled with -mips32r2 -mips16 -Os:
struct { int addr; } c;
struct command { int args[1]; };
unsigned short a;
fn1 (struct command *p1)
{
unsigned short d;
d = fn2 ();
a = p1->args[0];
fn3 (a);
if (c.addr)
{
fn4 (p1->args[0]);
return;
}
(&c)->addr = fn5 ();
fn6 (d);
}
Not sure how the constraint would/should exclude $sp-based address in LRA.
In this particular case, a spilled pseudo is changed to memory giving the
following RTL form:
(insn 30 29 31 4 (set (reg:SI 4 $4)
(and:SI (mem/c:SI (plus:SI (reg/f:SI 78 $frame)
(const_int 16 [0x10])) [7 %sfp+16 S4 A32])
(const_int 65535 [0xffff]))) shell.i:17 161 {*andsi3_mips16}
(expr_list:REG_DEAD (reg:SI 194 [ D.1469 ])
(nil)))
The operand 1 during alternative selection is not marked as a bad operand as it
is a memory
operand. $frame appears to be fine as it could be eliminated later to hard
register. No reloads
are inserted for the instructions concerned. Unless, $frame should be
temporarily eliminated
and then a reload would be inserted?
Regards,
Robert
