Richard Biener <rguent...@suse.de> writes:
> This removes the odd check of size_type_node when handling left-shifts
> as multiplications of 1 << N and instead uses the type as specified.
> It also moves left-shift handling next to multiplications where it
> semantically belongs.
>
> Boostrap and regtest pending on x86_64-unknown-linux-gnu.
>
> OK? (I failed to short-cut the wide_int_to_tree for a
> poly_int_cst_p bottom)
>
> Thanks,
> Richard.
>
> 2022-01-24 Richard Biener <rguent...@suse.de>
>
> * fold-const.cc (multiple_of_p): Re-write and move LSHIFT_EXPR
> handling.
> ---
> gcc/fold-const.cc | 33 ++++++++++++++++-----------------
> 1 file changed, 16 insertions(+), 17 deletions(-)
>
> diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
> index b155611578d..a0a4913c45e 100644
> --- a/gcc/fold-const.cc
> +++ b/gcc/fold-const.cc
> @@ -14068,7 +14068,7 @@ int
> multiple_of_p (tree type, const_tree top, const_tree bottom)
> {
> gimple *stmt;
> - tree t1, op1, op2;
> + tree op1, op2;
>
> if (operand_equal_p (top, bottom, 0))
> return 1;
> @@ -14114,6 +14114,21 @@ multiple_of_p (tree type, const_tree top, const_tree
> bottom)
> return (multiple_of_p (type, TREE_OPERAND (top, 1), bottom)
> || multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
>
> + case LSHIFT_EXPR:
> + /* Handle X << CST as X * (1 << CST) and only process the constant. */
> + if (TREE_CODE (TREE_OPERAND (top, 1)) == INTEGER_CST)
> + {
> + op1 = TREE_OPERAND (top, 1);
> + if (wi::gtu_p (TYPE_PRECISION (type), wi::to_wide (op1)))
> + {
> + wide_int mul_op
> + = wi::one (TYPE_PRECISION (type)) << wi::to_wide (op1);
> + return multiple_of_p (type,
> + wide_int_to_tree (type, mul_op), bottom);
> + }
> + }
> + return 0;
> +
LGTM. Sorry for the slow response.
I guess the condition could be written:
if (wi::to_widest (op1) < TYPE_PRECISION (type))
which might be more readable, and also avoids accidentally reinterpreting
a sign.
Thanks,
Richard
> case MINUS_EXPR:
> /* It is impossible to prove if op0 - op1 is multiple of bottom
> precisely, so be conservative here checking if both op0 and op1
> @@ -14133,22 +14148,6 @@ multiple_of_p (tree type, const_tree top, const_tree
> bottom)
> return (multiple_of_p (type, op1, bottom)
> && multiple_of_p (type, TREE_OPERAND (top, 0), bottom));
>
> - case LSHIFT_EXPR:
> - if (TREE_CODE (TREE_OPERAND (top, 1)) == INTEGER_CST)
> - {
> - op1 = TREE_OPERAND (top, 1);
> - /* const_binop may not detect overflow correctly,
> - so check for it explicitly here. */
> - if (wi::gtu_p (TYPE_PRECISION (TREE_TYPE (size_one_node)),
> - wi::to_wide (op1))
> - && (t1 = fold_convert (type,
> - const_binop (LSHIFT_EXPR, size_one_node,
> - op1))) != 0
> - && !TREE_OVERFLOW (t1))
> - return multiple_of_p (type, t1, bottom);
> - }
> - return 0;
> -
> CASE_CONVERT:
> /* Can't handle conversions from non-integral or wider integral type.
> */
> if ((TREE_CODE (TREE_TYPE (TREE_OPERAND (top, 0))) != INTEGER_TYPE)
