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c++: Fix up handling of vector CONSTRUCTORs with vectors in it in constexpr.cc [PR104226] 

The middle-end uses sometimes VECTOR_TYPE CONSTRUCTORs that contain
some other VECTOR_TYPE elements in it (should be with compatible element
size and smaller number of elements, e.g. a V8SImode vector can be
constructed as { V4SImode_var_1, V4SImode_var_2 }), and expansion of
__builtin_shufflevector emits these early, so constexpr.cc can see those
too.
constexpr.cc already has special cases for NULL index which is typical
for VECTOR_TYPE CONSTRUCTORs, and for VECTOR_TYPE CONSTRUCTORs that
contain just scalar elts that works just fine - init_subob_ctx just
returns on non-aggregate elts and get_or_insert_ctor_field has
  if (TREE_CODE (type) == VECTOR_TYPE && index == NULL_TREE)
    {
      CONSTRUCTOR_APPEND_ELT (CONSTRUCTOR_ELTS (ctor), index, NULL_TREE);
      return &CONSTRUCTOR_ELTS (ctor)->last();
    }
handling for it.  But for the vector in vector case init_subob_ctx would
try to create a sub-CONSTRUCTOR and even didn't handle the NULL index
case well, so instead of creating the sub-CONSTRUCTOR after the elts already
in it overwrote the first one.  So
(V8SImode) { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } }
became
(V8SImode) { 0, 0, 0, 0 }
The following patch fixes it by not forcing a sub-CONSTRUCTOR for this
vector in vector case.

2022-01-26  Jakub Jelinek  <jakub@redhat.com>

	PR c++/104226
	* constexpr.cc (init_subob_ctx): For vector ctors containing
	vector elements, ensure appending to the same ctor instead of
	creating another one.

	* g++.dg/cpp0x/constexpr-104226.C: New test.
This commit is contained in:
Jakub Jelinek 2022-01-26 19:40:29 +01:00
parent 7bd1e1296c
commit abea1c9a25
2 changed files with 22 additions and 0 deletions
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7
gcc/cp/constexpr.cc
View File

@ -4658,6 +4658,13 @@ init_subob_ctx (const constexpr_ctx *ctx, constexpr_ctx &new_ctx,
if (!AGGREGATE_TYPE_P (type) && !VECTOR_TYPE_P (type))
/* A non-aggregate member doesn't get its own CONSTRUCTOR. */
return;
if (VECTOR_TYPE_P (type)
&& VECTOR_TYPE_P (TREE_TYPE (ctx->ctor))
&& index == NULL_TREE)
/* A vector inside of a vector CONSTRUCTOR, e.g. when a larger
vector is constructed from smaller vectors, doesn't get its own
CONSTRUCTOR either. */
return;
/* The sub-aggregate initializer might contain a placeholder;
update object to refer to the subobject and ctor to refer to

15
gcc/testsuite/g++.dg/cpp0x/constexpr-104226.C Normal file
View File

@ -0,0 +1,15 @@
// PR c++/104226
// { dg-do compile }
// { dg-options "-Wno-psabi" }
typedef unsigned short __attribute__((__vector_size__(16))) U;
typedef unsigned int __attribute__((__vector_size__(16))) V;
typedef unsigned int __attribute__((__vector_size__(32))) W;
U
foo (void)
{
return __builtin_convertvector (__builtin_shufflevector ((V){}, (W){},
0, 0, 1, 0,
5, 5, 0, 2), U);
}