On Tue, Apr 11, 2023 at 07:26:07PM -0600, Jeff Law wrote:
> I did bootstrap on riscv, but not a regression test, that's spinning right
> now.
>
> Jeff
> diff --git a/gcc/combine.cc b/gcc/combine.cc
> index 22bf8e1ec89..c41d8a09b3b 100644
> --- a/gcc/combine.cc
> +++ b/gcc/combine.cc
> @@ -10055,9 +10055,10 @@ simplify_and_const_int_1 (scalar_int_mode mode, rtx
> varop,
>
> /* See what bits may be nonzero in VAROP. Unlike the general case of
> a call to nonzero_bits, here we don't care about bits outside
> - MODE. */
> + MODE unless WORD_REGISTER_OPERATIONS is true. */
I would have expected something like
WORD_REGISTER_OPERATIONS && known_le (GET_MODE_PRECISION (mode), BITS_PER_WORD)
as the condition to use word_mode, rather than just
WORD_REGISTER_OPERATIONS. In both spots. Because larger modes should be
used as is, not a narrower word_mode instead of them.
> - nonzero = nonzero_bits (varop, mode) & GET_MODE_MASK (mode);
> + enum machine_mode tmode = WORD_REGISTER_OPERATIONS ? word_mode : mode;
> + nonzero = nonzero_bits (varop, tmode) & GET_MODE_MASK (tmode);
>
> /* Turn off all bits in the constant that are known to already be zero.
> Thus, if the AND isn't needed at all, we will have CONSTOP ==
> NONZERO_BITS
> diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
> index 3b33afa2461..5f6f70491d8 100644
> --- a/gcc/simplify-rtx.cc
> +++ b/gcc/simplify-rtx.cc
> @@ -3752,7 +3752,10 @@ simplify_context::simplify_binary_operation_1
> (rtx_code code,
> return op0;
> if (HWI_COMPUTABLE_MODE_P (mode))
> {
> - HOST_WIDE_INT nzop0 = nonzero_bits (trueop0, mode);
> + /* When WORD_REGISTER_OPERATIONS is true, we need to know the
> + nonzero bits in WORD_MODE rather than MODE. */
> + HOST_WIDE_INT nzop0
> + = nonzero_bits (trueop0, WORD_REGISTER_OPERATIONS ? word_mode :
> mode);
> HOST_WIDE_INT nzop1;
> if (CONST_INT_P (trueop1))
> {
Regarding my earlier comments for this spot, the later code does
nzop1 = nonzero_bits (trueop1, mode);
/* If we are clearing all the nonzero bits, the result is zero. */
if ((nzop1 & nzop0) == 0
&& !side_effects_p (op0) && !side_effects_p (op1))
return CONST0_RTX (mode);
and because nonzero_bits in word_mode if it is wider might have just more
bits set above mode, but nzop1 will not have those bits set, I think it is
fine the way you wrote it (except for the precision check).
Jakub
