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| author | Jakub Jelinek <jakub@redhat.com> | 2020-07-20 10:24:19 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2020-07-20 10:24:19 +0200 |
| commit | e4f1cbc35b1e823a0a6e58eeca61c8c6ca351875 (patch) | |
| tree | baee51a3e02e958107cd446bb1587507df747e58 /gcc/gimple-fold.c | |
| parent | 83b171655dc0785262a444f5d5c2be7195977987 (diff) | |
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gimple-fold: Handle bitfields in fold_const_aggregate_ref_1 [PR93121]
When working on __builtin_bit_cast that needs to handle bitfields too,
I've made the following change to handle at least some bitfields in
fold_const_aggregate_ref_1 (those that have integral representative).
It already handles some, but only those that start and end at byte
boundaries.
2020-07-20 Jakub Jelinek <jakub@redhat.com>
PR libstdc++/93121
* gimple-fold.c (fold_const_aggregate_ref_1): For COMPONENT_REF
of a bitfield not aligned on byte boundaries try to
fold_ctor_reference DECL_BIT_FIELD_REPRESENTATIVE if any and
adjust it depending on endianity.
* gcc.dg/tree-ssa/pr93121-2.c: New test.
Diffstat (limited to 'gcc/gimple-fold.c')
| -rw-r--r-- | gcc/gimple-fold.c | 60 |
1 files changed, 58 insertions, 2 deletions
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c index dfda6db..81c77f7 100644 --- a/gcc/gimple-fold.c +++ b/gcc/gimple-fold.c @@ -7189,8 +7189,64 @@ fold_const_aggregate_ref_1 (tree t, tree (*valueize) (tree)) if (maybe_lt (offset, 0)) return NULL_TREE; - return fold_ctor_reference (TREE_TYPE (t), ctor, offset, size, - base); + tem = fold_ctor_reference (TREE_TYPE (t), ctor, offset, size, base); + if (tem) + return tem; + + /* For bit field reads try to read the representative and + adjust. */ + if (TREE_CODE (t) == COMPONENT_REF + && DECL_BIT_FIELD (TREE_OPERAND (t, 1)) + && DECL_BIT_FIELD_REPRESENTATIVE (TREE_OPERAND (t, 1))) + { + HOST_WIDE_INT csize, coffset; + tree field = TREE_OPERAND (t, 1); + tree repr = DECL_BIT_FIELD_REPRESENTATIVE (field); + if (INTEGRAL_TYPE_P (TREE_TYPE (repr)) + && size.is_constant (&csize) + && offset.is_constant (&coffset) + && (coffset % BITS_PER_UNIT != 0 + || csize % BITS_PER_UNIT != 0) + && !reverse + && BYTES_BIG_ENDIAN == WORDS_BIG_ENDIAN) + { + poly_int64 bitoffset; + poly_uint64 field_offset, repr_offset; + if (poly_int_tree_p (DECL_FIELD_OFFSET (field), &field_offset) + && poly_int_tree_p (DECL_FIELD_OFFSET (repr), &repr_offset)) + bitoffset = (field_offset - repr_offset) * BITS_PER_UNIT; + else + bitoffset = 0; + bitoffset += (tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field)) + - tree_to_uhwi (DECL_FIELD_BIT_OFFSET (repr))); + HOST_WIDE_INT bitoff; + int diff = (TYPE_PRECISION (TREE_TYPE (repr)) + - TYPE_PRECISION (TREE_TYPE (field))); + if (bitoffset.is_constant (&bitoff) + && bitoff >= 0 + && bitoff <= diff) + { + offset -= bitoff; + size = tree_to_uhwi (DECL_SIZE (repr)); + + tem = fold_ctor_reference (TREE_TYPE (repr), ctor, offset, + size, base); + if (tem && TREE_CODE (tem) == INTEGER_CST) + { + if (!BYTES_BIG_ENDIAN) + tem = wide_int_to_tree (TREE_TYPE (field), + wi::lrshift (wi::to_wide (tem), + bitoff)); + else + tem = wide_int_to_tree (TREE_TYPE (field), + wi::lrshift (wi::to_wide (tem), + diff - bitoff)); + return tem; + } + } + } + } + break; case REALPART_EXPR: case IMAGPART_EXPR: |