On February 18, 2020 4:56:08 PM GMT+01:00, Martin Jambor <mjam...@suse.cz>
wrote:
>Hi,
>
>[[no_unique_address]] C++ attribute can cause two fields of a
>RECORD_TYPE overlap, which currently confuses the totally scalarizing
>code into creating invalid access tree. For GCC 10, I'd like to
>simply disable total scalarization of types where this happens.
>
>For GCC 11 I'll write down a TODO item to enable total scalarization
>of cases like this where the problematic fields are basically empty -
>despite having a non-zero size - i.e. when they are just RECORD_TYPEs
>without any data fields.
>
>Bootstrapped and tested on x86_64, OK for trunk?
Ok.
Richard.
>Thanks,
>
>Martin
>
>2020-02-14 Martin Jambor <mjam...@suse.cz>
>
> PR tree-optimization/93667
> * tree-sra.c (scalarizable_type_p): Return false if record fields
> do not follow wach other.
>
> testsuite/
> * g++.dg/tree-ssa/pr93667.C: New test.
>---
> gcc/ChangeLog | 6 ++++++
> gcc/testsuite/ChangeLog | 5 +++++
> gcc/testsuite/g++.dg/tree-ssa/pr93667.C | 11 +++++++++++
> gcc/tree-sra.c | 14 ++++++++++++++
> 4 files changed, 36 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/tree-ssa/pr93667.C
>
>diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr93667.C
>b/gcc/testsuite/g++.dg/tree-ssa/pr93667.C
>new file mode 100644
>index 00000000000..d875f53d9ec
>--- /dev/null
>+++ b/gcc/testsuite/g++.dg/tree-ssa/pr93667.C
>@@ -0,0 +1,11 @@
>+// { dg-do compile }
>+// { dg-options "-O2 -std=c++2a" } */
>+
>+struct a {};
>+struct b { [[no_unique_address]] a aq; };
>+struct c {
>+ int d;
>+ [[no_unique_address]] b e;
>+};
>+c f() {return {};}
>+void g() { f(); }
>diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
>index 0cfac0a8192..4c7d651e6b9 100644
>--- a/gcc/tree-sra.c
>+++ b/gcc/tree-sra.c
>@@ -958,6 +958,9 @@ scalarizable_type_p (tree type, bool const_decl)
> if (type_contains_placeholder_p (type))
> return false;
>
>+ bool have_predecessor_field = false;
>+ HOST_WIDE_INT prev_pos = 0;
>+
> switch (TREE_CODE (type))
> {
> case RECORD_TYPE:
>@@ -966,6 +969,17 @@ scalarizable_type_p (tree type, bool const_decl)
> {
> tree ft = TREE_TYPE (fld);
>
>+ if (zerop (DECL_SIZE (fld)))
>+ continue;
>+
>+ HOST_WIDE_INT pos = int_bit_position (fld);
>+ if (have_predecessor_field
>+ && pos <= prev_pos)
>+ return false;
>+
>+ have_predecessor_field = true;
>+ prev_pos = pos;
>+
> if (DECL_BIT_FIELD (fld))
> return false;
>
