"Steve Ellcey " <sell...@imgtec.com> writes:
> Here is a patch for PR6400. The problem is that and_operands_ok was checking
> one operand to see if it was a memory_operand but MIPS16 addressing is more
> restrictive than what the general memory_operand allows. The fix was to
> call mips_classify_address if TARGET_MIPS16 is set because it will do a
> more complete mips16 addressing check and reject operands that do not meet
> the more restrictive requirements.
>
> I ran the GCC testsuite with no regressions and have included a test case as
> part of this patch.
>
> OK to checkin?
>
> Steve Ellcey
> sell...@imgtec.com
>
>
> 2016-01-26 Steve Ellcey <sell...@imgtec.com>
>
> PR target/68400
> * config/mips/mips.c (and_operands_ok): Add MIPS16 check.
>
>
>
> diff --git a/gcc/config/mips/mips.c b/gcc/config/mips/mips.c
> index dd54d6a..adeafa3 100644
> --- a/gcc/config/mips/mips.c
> +++ b/gcc/config/mips/mips.c
> @@ -8006,9 +8006,18 @@ mask_low_and_shift_p (machine_mode mode, rtx mask, rtx
> shift, int maxlen)
> bool
> and_operands_ok (machine_mode mode, rtx op1, rtx op2)
> {
> - return (memory_operand (op1, mode)
> - ? and_load_operand (op2, mode)
> - : and_reg_operand (op2, mode));
> +
> + if (memory_operand (op1, mode))
> + {
> + if (TARGET_MIPS16) {
> + struct mips_address_info addr;
> + if (!mips_classify_address (&addr, op1, mode, false))
> + return false;
> + }
Nit: brace formatting.
It looks like the patch only works by accident. The code above
is passing the MEM, rather than the address inside the MEM, to
mips_classify_address. Since (mem (mem ...)) is never valid on MIPS,
the effect is to disable the memory alternatives of *and<mode>3_mips16
unconditionally.
The addresses that occur in the testcase are valid as far as
mips_classify_address is concerned. FWIW, there shouldn't be any
difference between the addresses that memory_operand accepts and the
addresses that mips_classify_address accepts.
In theory, the "W" constraints in *and<mode>3_mips16 are supposed to
tell the target-independent code that this instruction cannot handle
constant addresses or stack-based addresses. That seems to be working
correctly during RA for the testcase. The problem comes in regcprop,
which ends up creating a second stack pointer rtx distinct from
stack_pointer_rtx:
(reg/f:SI 29 $sp [375])
(Note the ORIGINAL_REGNO of 375.) This then defeats the test in
mips_stack_address_p:
bool
mips_stack_address_p (rtx x, machine_mode mode)
{
struct mips_address_info addr;
return (mips_classify_address (&addr, x, mode, false)
&& addr.type == ADDRESS_REG
&& addr.reg == stack_pointer_rtx);
}
Change the == to rtx_equal_p and the test passes. I don't think that's
the correct fix though -- the fix is to stop a second stack pointer rtx
from being created.
Thanks,
Richard
