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varasm: Fix output_constructor where a RANGE_EXPR index needs to skip some elts [PR94303]

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The following testcase is miscompiled, because output_constructor doesn't
output the initializer correctly.  The FE creates {[1...2] = 9} in this
case, and we emit .long 9; long 9; .zero 8 instead of the expected
.zero 8; .long 9; .long 9.  If the CONSTRUCTOR is {[1] = 9, [2] = 9},
output_constructor_regular_field has code to notice that the current
location (local->total_bytes) is smaller than the location we want to write
to (1*sizeof(elt)) and will call assemble_zeros to skip those.  But
RANGE_EXPRs are handled by a different function which didn't do this,
so for RANGE_EXPRs we emitted them properly only if local->total_bytes
was always equal to the location where the RANGE_EXPR needs to start.

2020-03-25  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/94303
	* varasm.c (output_constructor_array_range): If local->index
	RANGE_EXPR doesn't start at the current location in the constructor,
	skip needed number of bytes using assemble_zeros or assert we don't
	go backwards.

	PR middle-end/94303
	* g++.dg/torture/pr94303.C: New test.
This commit is contained in:
Jakub Jelinek 2020-03-25 09:21:05 +01:00
parent 158cccea0d
commit 5f18995e23
4 changed files with 46 additions and 0 deletions
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6
gcc/ChangeLog
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@ -1,5 +1,11 @@
2020-03-25 Jakub Jelinek <jakub@redhat.com>
PR middle-end/94303
* varasm.c (output_constructor_array_range): If local->index
RANGE_EXPR doesn't start at the current location in the constructor,
skip needed number of bytes using assemble_zeros or assert we don't
go backwards.
PR c++/94223
* langhooks.c (lhd_set_decl_assembler_name): Use a static ulong
counter instead of DECL_UID.

3
gcc/testsuite/ChangeLog
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@ -1,5 +1,8 @@
2020-03-25 Jakub Jelinek <jakub@redhat.com>
PR middle-end/94303
* g++.dg/torture/pr94303.C: New test.
PR c++/94223
* g++.dg/opt/pr94223.C: New test.

17
gcc/testsuite/g++.dg/torture/pr94303.C Normal file
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@ -0,0 +1,17 @@
// PR middle-end/94303
// { dg-do run }
struct A {
int d = 9;
A () = default;
A (int x) : d(x) {}
void foo () { if (d < 1) __builtin_abort (); }
};
A a[3] = { 1 };
int
main ()
{
a[2].foo ();
}

20
gcc/varasm.c
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@ -5152,6 +5152,26 @@ struct oc_local_state {
static void
output_constructor_array_range (oc_local_state *local)
{
/* Perform the index calculation in modulo arithmetic but
sign-extend the result because Ada has negative DECL_FIELD_OFFSETs
but we are using an unsigned sizetype. */
unsigned prec = TYPE_PRECISION (sizetype);
offset_int idx = wi::sext (wi::to_offset (TREE_OPERAND (local->index, 0))
- wi::to_offset (local->min_index), prec);
tree valtype = TREE_TYPE (local->val);
HOST_WIDE_INT fieldpos
= (idx * wi::to_offset (TYPE_SIZE_UNIT (valtype))).to_short_addr ();
/* Advance to offset of this element. */
if (fieldpos > local->total_bytes)
{
assemble_zeros (fieldpos - local->total_bytes);
local->total_bytes = fieldpos;
}
else
/* Must not go backwards. */
gcc_assert (fieldpos == local->total_bytes);
unsigned HOST_WIDE_INT fieldsize
= int_size_in_bytes (TREE_TYPE (local->type));