On Thu, Oct 29, 2015 at 8:18 PM, Alan Lawrence <alan.lawre...@arm.com> wrote:
> This is in response to https://gcc.gnu.org/ml/gcc/2015-10/msg00097.html, where
> Richi points out that CONSTRUCTOR elements are not necessarily ordered.
>
> I wasn't sure of a good naming convention for the new
> get_ctor_element_at_index,
> other suggestions welcome.
get_array_ctor_element_at_index
(ok it also handles vectors).
Ok with that change.
Richard.
> gcc/ChangeLog:
>
> * gimple-fold.c (fold_array_ctor_reference): Move searching code to:
> * fold-const.c (get_ctor_element_at_index): New.
> (fold): Remove binary-search through CONSTRUCTOR, call previous.
>
> * fold-const.h (get_ctor_element_at_index): New.
> ---
> gcc/fold-const.c | 93
> ++++++++++++++++++++++++++++++++++++++++---------------
> gcc/fold-const.h | 1 +
> gcc/gimple-fold.c | 47 ++--------------------------
> 3 files changed, 72 insertions(+), 69 deletions(-)
>
> diff --git a/gcc/fold-const.c b/gcc/fold-const.c
> index de45a2c..5d27b91 100644
> --- a/gcc/fold-const.c
> +++ b/gcc/fold-const.c
> @@ -12018,6 +12018,72 @@ fold_ternary_loc (location_t loc, enum tree_code
> code, tree type,
> } /* switch (code) */
> }
>
> +/* Gets the element ACCESS_INDEX from CTOR, which must be a CONSTRUCTOR. */
> +
> +tree
> +get_ctor_element_at_index (tree ctor, offset_int access_index)
> +{
> + tree index_type = NULL_TREE;
> + offset_int low_bound = 0;
> +
> + if (TREE_CODE (TREE_TYPE (ctor)) == ARRAY_TYPE)
> + {
> + tree domain_type = TYPE_DOMAIN (TREE_TYPE (ctor));
> + if (domain_type && TYPE_MIN_VALUE (domain_type))
> + {
> + /* Static constructors for variably sized objects makes no sense. */
> + gcc_assert (TREE_CODE (TYPE_MIN_VALUE (domain_type)) == INTEGER_CST);
> + index_type = TREE_TYPE (TYPE_MIN_VALUE (domain_type));
> + low_bound = wi::to_offset (TYPE_MIN_VALUE (domain_type));
> + }
> + }
> +
> + if (index_type)
> + access_index = wi::ext (access_index, TYPE_PRECISION (index_type),
> + TYPE_SIGN (index_type));
> +
> + offset_int index = low_bound - 1;
> + if (index_type)
> + index = wi::ext (index, TYPE_PRECISION (index_type),
> + TYPE_SIGN (index_type));
> +
> + offset_int max_index;
> + unsigned HOST_WIDE_INT cnt;
> + tree cfield, cval;
> +
> + FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
> + {
> + /* Array constructor might explicitely set index, or specify range
> + * or leave index NULL meaning that it is next index after previous
> + * one. */
> + if (cfield)
> + {
> + if (TREE_CODE (cfield) == INTEGER_CST)
> + max_index = index = wi::to_offset (cfield);
> + else
> + {
> + gcc_assert (TREE_CODE (cfield) == RANGE_EXPR);
> + index = wi::to_offset (TREE_OPERAND (cfield, 0));
> + max_index = wi::to_offset (TREE_OPERAND (cfield, 1));
> + }
> + }
> + else
> + {
> + index += 1;
> + if (index_type)
> + index = wi::ext (index, TYPE_PRECISION (index_type),
> + TYPE_SIGN (index_type));
> + max_index = index;
> + }
> +
> + /* Do we have match? */
> + if (wi::cmpu (access_index, index) >= 0
> + && wi::cmpu (access_index, max_index) <= 0)
> + return cval;
> + }
> + return NULL_TREE;
> +}
> +
> /* Perform constant folding and related simplification of EXPR.
> The related simplifications include x*1 => x, x*0 => 0, etc.,
> and application of the associative law.
> @@ -12094,31 +12160,8 @@ fold (tree expr)
> && TREE_CODE (op0) == CONSTRUCTOR
> && ! type_contains_placeholder_p (TREE_TYPE (op0)))
> {
> - vec<constructor_elt, va_gc> *elts = CONSTRUCTOR_ELTS (op0);
> - unsigned HOST_WIDE_INT end = vec_safe_length (elts);
> - unsigned HOST_WIDE_INT begin = 0;
> -
> - /* Find a matching index by means of a binary search. */
> - while (begin != end)
> - {
> - unsigned HOST_WIDE_INT middle = (begin + end) / 2;
> - tree index = (*elts)[middle].index;
> -
> - if (TREE_CODE (index) == INTEGER_CST
> - && tree_int_cst_lt (index, op1))
> - begin = middle + 1;
> - else if (TREE_CODE (index) == INTEGER_CST
> - && tree_int_cst_lt (op1, index))
> - end = middle;
> - else if (TREE_CODE (index) == RANGE_EXPR
> - && tree_int_cst_lt (TREE_OPERAND (index, 1), op1))
> - begin = middle + 1;
> - else if (TREE_CODE (index) == RANGE_EXPR
> - && tree_int_cst_lt (op1, TREE_OPERAND (index, 0)))
> - end = middle;
> - else
> - return (*elts)[middle].value;
> - }
> + if (tree val = get_ctor_element_at_index (op0, wi::to_offset
> (op1)))
> + return val;
> }
>
> return t;
> diff --git a/gcc/fold-const.h b/gcc/fold-const.h
> index ee74dc8..1fa6ee0 100644
> --- a/gcc/fold-const.h
> +++ b/gcc/fold-const.h
> @@ -73,6 +73,7 @@ extern tree fold_build_call_array_loc (location_t, tree,
> tree, int, tree *);
> #define fold_build_call_array_initializer(T1,T2,N,T4)\
> fold_build_call_array_initializer_loc (UNKNOWN_LOCATION, T1, T2, N, T4)
> extern tree fold_build_call_array_initializer_loc (location_t, tree, tree,
> int, tree *);
> +extern tree get_ctor_element_at_index (tree, offset_int);
> extern bool fold_convertible_p (const_tree, const_tree);
> #define fold_convert(T1,T2)\
> fold_convert_loc (UNKNOWN_LOCATION, T1, T2)
> diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
> index 85ff018..823d952 100644
> --- a/gcc/gimple-fold.c
> +++ b/gcc/gimple-fold.c
> @@ -5308,13 +5308,10 @@ fold_array_ctor_reference (tree type, tree ctor,
> unsigned HOST_WIDE_INT size,
> tree from_decl)
> {
> - unsigned HOST_WIDE_INT cnt;
> - tree cfield, cval;
> offset_int low_bound;
> offset_int elt_size;
> - offset_int index, max_index;
> offset_int access_index;
> - tree domain_type = NULL_TREE, index_type = NULL_TREE;
> + tree domain_type = NULL_TREE;
> HOST_WIDE_INT inner_offset;
>
> /* Compute low bound and elt size. */
> @@ -5324,7 +5321,6 @@ fold_array_ctor_reference (tree type, tree ctor,
> {
> /* Static constructors for variably sized objects makes no sense. */
> gcc_assert (TREE_CODE (TYPE_MIN_VALUE (domain_type)) == INTEGER_CST);
> - index_type = TREE_TYPE (TYPE_MIN_VALUE (domain_type));
> low_bound = wi::to_offset (TYPE_MIN_VALUE (domain_type));
> }
> else
> @@ -5346,9 +5342,6 @@ fold_array_ctor_reference (tree type, tree ctor,
> access_index = wi::udiv_trunc (offset_int (offset / BITS_PER_UNIT),
> elt_size);
> access_index += low_bound;
> - if (index_type)
> - access_index = wi::ext (access_index, TYPE_PRECISION (index_type),
> - TYPE_SIGN (index_type));
>
> /* And offset within the access. */
> inner_offset = offset % (elt_size.to_uhwi () * BITS_PER_UNIT);
> @@ -5357,43 +5350,9 @@ fold_array_ctor_reference (tree type, tree ctor,
> care to fold accesses spanning multiple array indexes. */
> if (inner_offset + size > elt_size.to_uhwi () * BITS_PER_UNIT)
> return NULL_TREE;
> + if (tree val = get_ctor_element_at_index (ctor, access_index))
> + return fold_ctor_reference (type, val, inner_offset, size, from_decl);
>
> - index = low_bound - 1;
> - if (index_type)
> - index = wi::ext (index, TYPE_PRECISION (index_type),
> - TYPE_SIGN (index_type));
> -
> - FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval)
> - {
> - /* Array constructor might explicitely set index, or specify range
> - or leave index NULL meaning that it is next index after previous
> - one. */
> - if (cfield)
> - {
> - if (TREE_CODE (cfield) == INTEGER_CST)
> - max_index = index = wi::to_offset (cfield);
> - else
> - {
> - gcc_assert (TREE_CODE (cfield) == RANGE_EXPR);
> - index = wi::to_offset (TREE_OPERAND (cfield, 0));
> - max_index = wi::to_offset (TREE_OPERAND (cfield, 1));
> - }
> - }
> - else
> - {
> - index += 1;
> - if (index_type)
> - index = wi::ext (index, TYPE_PRECISION (index_type),
> - TYPE_SIGN (index_type));
> - max_index = index;
> - }
> -
> - /* Do we have match? */
> - if (wi::cmpu (access_index, index) >= 0
> - && wi::cmpu (access_index, max_index) <= 0)
> - return fold_ctor_reference (type, cval, inner_offset, size,
> - from_decl);
> - }
> /* When memory is not explicitely mentioned in constructor,
> it is 0 (or out of range). */
> return build_zero_cst (type);
> --
> 1.9.1
>
