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c++: build initializer_list<string> in a loop [PR105838]

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The previous patch avoided building an initializer_list<string> at all when
building a vector<string>, but in situations where that isn't possible, we
could still build the initializer_list with a loop over a constant array.

This is represented using a VEC_INIT_EXPR, which required adjusting a couple
of places that expected the initializer array to have the same type as the
target array and fixing build_vec_init not to undo our efforts.

	PR c++/105838

gcc/cp/ChangeLog:

	* call.cc (convert_like_internal) [ck_list]: Use
	maybe_init_list_as_array.
	* constexpr.cc (cxx_eval_vec_init_1): Init might have
	a different type.
	* tree.cc (build_vec_init_elt): Likewise.
	* init.cc (build_vec_init): Handle from_array from a
	TARGET_EXPR.  Retain TARGET_EXPR of a different type.

gcc/testsuite/ChangeLog:

	* g++.dg/tree-ssa/initlist-opt2.C: New test.
This commit is contained in:
Jason Merrill 2022-12-06 18:10:48 -05:00
parent d081807d8d
commit bd0485f20f
5 changed files with 48 additions and 8 deletions
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11
gcc/cp/call.cc
View file

@ -8501,7 +8501,16 @@ convert_like_internal (conversion *convs, tree expr, tree fn, int argnum,
unsigned len = CONSTRUCTOR_NELTS (expr);
tree array;
if (len)
if (tree init = maybe_init_list_as_array (elttype, expr))
{
elttype = cp_build_qualified_type
(elttype, cp_type_quals (elttype) | TYPE_QUAL_CONST);
array = build_array_of_n_type (elttype, len);
array = build_vec_init_expr (array, init, complain);
array = get_target_expr (array);
array = cp_build_addr_expr (array, complain);
}
else if (len)
{
tree val; unsigned ix;

6
gcc/cp/constexpr.cc
View file

@ -5255,12 +5255,12 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init,
else
{
/* Copying an element. */
gcc_assert (same_type_ignoring_top_level_qualifiers_p
(atype, TREE_TYPE (init)));
eltinit = cp_build_array_ref (input_location, init, idx, complain);
if (!lvalue_p (init))
eltinit = move (eltinit);
eltinit = force_rvalue (eltinit, complain);
eltinit = (perform_implicit_conversion_flags
(elttype, eltinit, complain,
LOOKUP_IMPLICIT|LOOKUP_NO_NARROWING));
eltinit = cxx_eval_constant_expression (&new_ctx, eltinit, lval,
non_constant_p, overflow_p);
}

13
gcc/cp/init.cc
View file

@ -4420,7 +4420,9 @@ build_vec_init (tree base, tree maxindex, tree init,
/* Look through the TARGET_EXPR around a compound literal. */
if (init && TREE_CODE (init) == TARGET_EXPR
&& TREE_CODE (TARGET_EXPR_INITIAL (init)) == CONSTRUCTOR
&& from_array != 2)
&& from_array != 2
&& (same_type_ignoring_top_level_qualifiers_p
(TREE_TYPE (init), atype)))
init = TARGET_EXPR_INITIAL (init);
if (tree vi = get_vec_init_expr (init))
@ -4546,7 +4548,14 @@ build_vec_init (tree base, tree maxindex, tree init,
{
if (lvalue_kind (init) & clk_rvalueref)
xvalue = true;
base2 = decay_conversion (init, complain);
if (TREE_CODE (init) == TARGET_EXPR)
{
/* Avoid error in decay_conversion. */
base2 = decay_conversion (TARGET_EXPR_SLOT (init), complain);
base2 = cp_build_compound_expr (init, base2, tf_none);
}
else
base2 = decay_conversion (init, complain);
if (base2 == error_mark_node)
return error_mark_node;
itype = TREE_TYPE (base2);

2
gcc/cp/tree.cc
View file

@ -785,8 +785,6 @@ build_vec_init_elt (tree type, tree init, tsubst_flags_t complain)
releasing_vec argvec;
if (init && !BRACE_ENCLOSED_INITIALIZER_P (init))
{
gcc_assert (same_type_ignoring_top_level_qualifiers_p
(type, TREE_TYPE (init)));
tree init_type = strip_array_types (TREE_TYPE (init));
tree dummy = build_dummy_object (init_type);
if (!lvalue_p (init))

24
gcc/testsuite/g++.dg/tree-ssa/initlist-opt2.C Normal file
View file

@ -0,0 +1,24 @@
// PR c++/105838
// { dg-additional-options -fdump-tree-gimple }
// { dg-do compile { target c++11 } }
// Check that we call the basic_string constructor once (and define it once).
// { dg-final { scan-tree-dump-times {>::basic_string} 2 "gimple" } }
#include <string>
void g (const void *);
void f (const char *p)
{
std::initializer_list<std::string> lst = {
"aahing", "aaliis", "aarrgh", "abacas", "abacus", "abakas", "abamps", "abands", "abased", "abaser", "abases", "abasia",
"abated", "abater", "abates", "abatis", "abator", "abattu", "abayas", "abbacy", "abbess", "abbeys", "abbots", "abcees",
"abdabs", "abduce", "abduct", "abears", "abeigh", "abeles", "abelia", "abends", "abhors", "abided", "abider", "abides",
"abject", "abjure", "ablate", "ablaut", "ablaze", "ablest", "ablets", "abling", "ablins", "abloom", "ablush", "abmhos",
"aboard", "aboded", "abodes", "abohms", "abolla", "abomas", "aboral", "abords", "aborne", "aborts", "abound", "abouts",
"aboves", "abrade", "abraid", "abrash", "abrays", "abrazo", "abrege", "abrins", "abroad", "abrupt", "abseil", "absent",
};
g(&lst);
}